ASA 2013

Refresher Course Lectures Anesthesiology 2013 American Society of Anesthesiologists. All rights reserved. Note: This publication contains material copyrighted by others. Individual refresher course lectures are reprinted by ASA with permission. Reprinting or using individual refresher course lectures contained herein is strictly prohibited without permission from the authors/copyright holders.

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Current Controversies in Adult Outpatient Anesthesia

Jeffrey L. Apfelbaum, M.D. Chicago,Illinois

Introduction

The fast paced world of ambulatory anesthesiology continues to present anesthesiologists with an ever-changing array of challenges. This Refresher Course will provide an update on current controversial issues in adult outpatient anesthesia, including fast tracking; preoperative assessment, evaluation, and preparation; recent changes to ASA Basic Anesthesia Monitoring Standards; ramifications of recent changes to Interpretative Guidelines issued by the Center for Medicare and Medicaid Services (CMS) on our practice; and Computer Assisted Personalized Sedation (CAPS). Additionally we will consider a variety of breaking news areas of controversy which may include topics such as patients with obesity/modified metabolic syndrome; advances in and recommendations to enhance perioperative communication; treatment decisions for patients with coronary artery stents; opportunities to incorporate ones personal outcomes data into your patient care plan and potential effect choice of anesthetic on cancer recurrence rates.

Fast Tracking: Eliminating Intensive Post-Operative Care in Same Day Surgery Patients Using Short Acting Fast Emergence Anesthetics

Many anesthetics have the pharmacokinetic and pharmacodynamic advantages of a shorter duration of action and a more rapid rate of recovery which permit a faster emergence from anesthesia compared with their predecessors. Less than 30 years ago, it was unthinkable that patients would be able to return home on the day of surgery. Today, advances in surgery and anesthesiology make it possible to perform the vast majority of all surgical procedures, safely and effectively on an ambulatory basis, with many patients ready to be reunited with their families within minutes of emergence from anesthesia. In todays cost sensitive healthcare environment, the processes of ambulatory surgical care must be continually re-evaluated to take advantage of advances in technology and pharmacology and to optimize efficiency of the ambulatory surgical care without detriment to patient safety and satisfaction.

Traditionally, ambulatory surgical patients go from the operating room to the postanesthesia care unit (PACU) or recovery room (a highly specialized intensive care unit) for their immediate postoperative recovery from anesthesia and then to a second stage recovery unit (SSRU) for preparation for home readiness. By its very nature as a specialized ICU, the PACU is an expensive, labor-intensive environment. After a set of recovery criteria 1, 2, 3 are met in the PACU, the patient is usually transferred to the SSRU. In the SSRU, the patient-to-nurse ratio is considerably higher (i.e., nursing care in the SSRU is less labor intensive) than in the PACU. Only basic monitoring and observation are performed as the patient and his or her escort are prepared for imminent discharge to home. Because of the rapid recovery of patients undergoing anesthesia with the shorter acting, faster emergence anesthetics, some have questioned if all ambulatory surgical patients need to receive intensive postoperative care in the PACU setting or whether first stage recovery from anesthesia can be achieved safely while still in the operating room (at least for some patients), thereby resulting in enormous potential savings.

The SAFE study evaluates the impact of selective patient bypass of the PACU on both the outcomes of ambulatory surgical patients and the use of resources in the surgical arena.4 This study was designed to evaluate the rapid recovery of patients undergoing ambulatory surgery using short-acting, fast emergence anesthetic agents and to determine if policies and procedures could be developed that would allow patients to safely bypass first stage


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post-anesthesia care units (PACU) and whether such changes in the recovery paradigm would result in financial savings for the surgical center. Five community based facilities (hospitals or surgery centers) participated in this prospective observational study. While in the operating room at the end of the surgical procedure, anesthesiologists were asked to assess all ambulatory surgical patients for recovery using standardizing discharge criteria typically used at the end of a PACU stay (Table 1). If the patient met the discharge criteria, they were transferred from the OR directly to the less labor intensive second stage recovery unit (SSRU). Financial data were provided from all five sites detailing all costs associated with the recovery process. Clinical data on every elective ASA 1, 2 and 3 ambulatory surgical patient were collected over a three month period. During month one, data collected established a baseline of case mix, time stamps, adverse events, bypass rates, and financial profile. During month two, an educational intervention was provided on a multi-disciplinary basis to all units in the surgical center discussing the implications of the bypass paradigm. After implementation of the paradigm (month three) weekly feedback reports were provided to the site featuring the key outcomes of the study, and these reports were distributed to the health care providers. Nearly 5,000 patients were entered into the study. The overall bypass rate increased from 15.9% in the baseline month to 58.9% in the month following the educational intervention (p < 0.0001). The change in process in this study went beyond reducing time spent in the PACU to eliminating the time spent in the PACU while not increasing the time spent in the operating room or SSRU. In fact, the average (SD) time spent in the SSRU was significantly shorter for patients who bypassed the PACU than for those who did not bypass the PACU. There were no significant differences in other parameters of patient outcome. Annualized savings ranged from $50,000 to $160,000 per site.

The Hows And Whys Of Preoperative Evaluation

The continued growth of outpatient surgery has created new roles for the anesthesiologist which seemingly demands skills in addition to "giving a good anesthetic." The times from induction to emergence are no longer the only important role for the perioperative physician. Particularly in the freestanding and office environments, it is often the anesthesiologist who is most involved in the direct medical care of the patient; we are the physicians who must insure that the patient is appropriately screened, evaluated, and informed prior to the day of surgery. Indeed, the anesthesiologist/patient relationship which sometimes develops often takes on a primary care quality. Although sometimes difficult to arrange, the preoperative interview and evaluation by a consultant anesthesiologist (particularly in high risk patients) can be extraordinarily beneficial. In addition to lessening anxiety about the surgery and anesthesia, in most cases, the anesthesiologist will be able to identify potential medical problems in advance, determine their etiology, and if indicated, initiate appropriate corrective measures. Additionally, the ambulatory anesthesiologist can play a critically important role in assuring that the patient understands and complies with preoperative instructions. In most facilities, the goal is to resolve preoperative problems well in advance of the day of surgery, thereby minimizing the numbers of both cancellations and complications.

At the present time, there are several commonly used approaches to screening patients for ambulatory surgery. These include: (1) facility visit prior to the day of surgery, (2) office visit prior to the day of surgery, (3) telephone interviews/no visit, (4) review of health survey/no visit, (5) preoperative screening and visit on the morning of surgery, (6) virtual visit via the internet/no physical visit, and (7) the use of telemedicine technology. Each system has its own advantages and disadvantages.

Should Patient Age or ASA Physical Status Influence Case Selection?

Although the vast majority of individuals scheduled for outpatient surgery are relatively healthy (ASA Physical Status 1 and 2), practitioners are constantly being pressured by third party payors to consider "simple outpatient surgery" for patients with significant baseline co-morbidities. A survey of members of the Society for Ambulatory Anesthesia (SAMBA) revealed that half the respondents felt that their practice pushes the envelope of patient safety by performing outpatient surgery on patients with serious pre-existing conditions, and that 40% of respondents felt that their practice pushes the envelope of patient safety by performing complex or lengthy surgical procedures on outpatients. In the past, many individuals had arbitrarily stated that freestanding ambulatory surgical facilities were severely limited in the type of patients they could anesthetize, particularly with regard to age and physical status. Clinical experience, however, suggests otherwise. In a retrospective study of over 1,500 cases of patients anesthetized for ambulatory surgery, Meridy6 was unable to demonstrate an age-related effect on the duration of recovery or the incidence of postoperative complications. With regard to the issue of physical status, in a prospective study involving over 13,000 patients at a freestanding ambulatory surgical center, Natof 7 concluded


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that ASA 3 patients whose systemic diseases were well controlled preoperatively were at no higher risk for postoperative complications than ASA 1 or 2 patients. Chung examined predictors of adverse events in ambulatory surgery in the elderly, as well as factors contributing to prolonged stay after ambulatory surgery in elderly patients. This data demonstrated that outpatient surgery is safe in this patient population, with elderly patients sustaining more minor cardiovascular events than their younger counterparts, and less postoperative nausea and vomiting, pain, and drowsiness.8, 9. It is clear that geriatric and higher risk (physical status 3 and 4) patients may be considered acceptable candidates for outpatient surgery if their systemic diseases are well controlled and the patients medical condition is optimized preoperatively.

The Inappropriate Patient - Who's OK And Who's Not

There are few data to reliably categorize the inappropriate adult surgical outpatient. As anesthesiologists have become more experienced with the anesthetic management of the problem surgical outpatient, the list of "inappropriate" patients has dwindled. We must individualize our decision with regard to each patient; with few exceptions, the appropriateness of a case for outpatient surgery is determined by a combination of factors including patient considerations, surgical procedure, anesthetic technique, and anesthesiologist's comfort level.

At the University of Chicago Medical Center, we have distinguished several groups of patients who may not be appropriate candidates for ambulatory surgery. As one might expect, this list is frequently modified to adapt to the ever-changing conditions of our social and medicolegal environment.

Unstable ASA Physical Status 3 and 4: At the present time we are reluctant to proceed with elective ambulatory surgery in a medically unstable patient. Instead, we use our anesthesia perioperative medicine clinic (APMC) to screen these patients, and together with the primary care surgeon or interventionalist, establish a plan to proceed with the surgery or intervention after medical stabilization. Contrary to the original "ground rules" of ambulatory surgery, studies involving hundreds of thousands of patients seem to suggest that neither increasing age nor the presence of stable pre-existing disease affect the incidence of postoperative complications in the surgical outpatient.

Malignant Hyperpyrexia: In our facility, overnight hospitalization and observation is usually indicated for patients with a history of malignant hyperpyrexia or with identified susceptibility to malignant hyperpyrexia. However, patients who are well educated, have a good understanding of their disease process, and have ready access to medical care may be treated as outpatients by some centers.

Complex Morbid Obesity/Complex Sleep Apnea: Although patients who have a history of sleep apnea or who are morbidly obese without systemic disease are acceptable candidates for ambulatory surgery, we prefer overnight hospitalization and postoperative observation for morbidly obese surgical patients with significant pre-existing cardiac, pulmonary, hepatic or renal compromise or those patients with a history of complex sleep apnea. Practice guidelines for the perioperative management of patients with obstructive sleep apnea have recently been developed by the American Society of Anesthesiologists and offer recommendations for preoperative evaluation, preoperative preparation, intraoperative management, postoperative management, and site of surgery (inpatient vs. outpatient).10

Acute Substance Abuse: Because of the increased likelihood of acute untoward cardiovascular responses when one administers an anesthetic to a patient who has recently abused illicit drugs, we preoperatively counsel these patients and inform them that any sign of recent drug abuse on the day of surgery will result in immediate cancellation of their anesthetic. We tell them that no elective surgical procedure "is worth dying for" and encourage their preoperative participation in a rehabilitation program.

Anesthesiology directed perioperative medicine clinics are increasingly used to optimize the medical condition of a patient in preparation for surgery. These clinics have been shown to enhance patient safety11, improve patient satisfaction 12,13, minimize preoperative consultation14, and reduce day of surgery case cancellations and case postponements.15

Changes to the ASA Standards for Basic Anesthesia Monitoring


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For the first time in nearly a decade, there has been a significant change to the ASA Standards for Basic Anesthesia Monitoring.16 The standard for monitoring of ventilation has undergone significant revision: VENTILATION: 3.2.4: During regional anesthesia (with no sedation) or local anesthesia (with no sedation), the adequacy of ventilation shall be evaluated by continual observation of qualitative clinical signs. During moderate or deep sedation the adequacy of ventilation shall be evaluated by continual observation of qualitative clinical signs and monitoring for the presence of exhaled carbon dioxide unless precluded or invalidated by the nature of the patient, procedure, or equipment. Many physicians have asked if these standards apply to cases where sedation is administered in out of operating room locations. The Centers for Medicare and Medicaid (CMS) Revised Hospital Anesthesia Services Interpretative Guidelines seemingly provide guidance on this issue. The first section in these Interpretative Guidelines is entitled Types of Anesthesia Services and the first bullet in this section begins as follows: Anesthesia services, which include both anesthesia and analgesia, are provided along a continuum, ranging from the application of local anesthetics for minor procedures to general anesthesia for patients who require loss of consciousness as well as control of vital body functions in order to tolerate invasive operative procedures. This continuum also includes minimal sedation, moderate sedation/analgesia (conscious sedation), monitored anesthesia care (MAC), and regional anesthesia.

CMS Issues Revised Hospital Anesthesia Services Interpretive Guidelines

CMS has recently issued significant revisions to the Anesthesia Services Interpretive Guidelines.16 These included significant revisions to the CMS compliance requirements for both pre and post anesthesia evaluations, as well as a requirement that heretofore, ALL anesthesia and sedation services (including mild, moderate, and deep sedation) , regardless of providers MUST be organized into a single anesthesia service under the direction of a qualified doctor of medicine or doctor of osteopathy. Specific portions of these Interpretive Guidelines will be addressed during the presentation.

Computer-Assisted Personalized Sedation (CAPS)

Ethicon Endo-Surgery, Inc. has developed a computer-assisted personalized sedation system (trade name SEDASYS) According to the manufacturer, the SEDASYS System is the first computer-assisted personalized sedation (CAPS) system designed for physician/nurse teams to provide minimal-to-moderate sedation levels with propofol. By integrating drug delivery and patient monitoring, the SEDASYS System enables physician/nurse teams to deliver personalized sedation. It automatically detects and responds to signs of over-sedation (oxygen desaturation and low respiratory rate/apnea) by stopping or reducing delivery of propofol, increasing oxygen delivery and automatically instructing patients to take a deep breath.

On May 28, 2009, the Anesthesia and Respiratory Therapy Devices Advisory Committee of the US Food and Drug Administration (FDA) concluded its deliberations and recommended to the FDA that the SEDASYS device be approvable for the administration of propofol by physician/nurse teams for the initiation and maintenance of minimal to moderate sedation during screening and diagnostic procedures in patients undergoing colonoscopy and esophagoduodenoscopy procedures with the following conditions: 1) The device may only be used in adult patients (ASA I, II, and III) 70 years old or younger; 2) The device may only be used in the presence of a 3 person clinical team where one person shall have the sole responsibility of monitoring the patient, the device and managing the patient's airway. This dedicated person must have advanced training and at least the skills of a nurse; 3) Physicians utilizing the device must complete training in advanced airway management, pharmacology of propofol and opioids, patient selection, monitor training (such as SpO2 monitoring), device set-up and maintenance with the training provided by a clinician with credentials to provide deep sedation to general anesthesia. In addition, there needs to be a program established for ongoing maintenance of training; 4) The manufacturer must complete all post-marketing studies as proposed at the time of the Advisory Panel hearing. 5) The product launch is controlled.

On several occasions, representatives of the company have suggested that the device is compliant with ASA guidelines on sedation/analgesia by non-anesthesiologists; as a result of this claim both medical professionals and lay people have occasionally erroneously concluded that the device is consistent with ASA standards, guidelines, statements and/or policies.17 Indeed, some individuals have mistakenly concluded that ASA has


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endorsed the product. However, this conclusion is erroneous. In the AANA-ASA Joint Statement Regarding Propofol Administration (April 14, 2004) the ASA position regarding the use of propofol is clearly stated as follows:18 Whenever propofol is used for sedation/anesthesia, it should be administered only by persons trained in the administration of general anesthesia, who are not simultaneously involved in these surgical or diagnostic procedures. This restriction is concordant with specific language in the propofol package insert, and failure to follow these recommendations could put patients at increased risk of significant injury or death.

In April 2010, Johnson & Johnson, the parent company of Ethicon-Endo Surgery, Inc., announced that the FDA sent the company a not approvable letter for the SEDASYS Computer Assisted Personalized Sedation System. The company had appealed this decision and on May 10, 2013 the company announced that the FDA had granted PMA approval for the device. The SEDASYS System is expected to be introduced on a limited basis beginning in 2014. The company will collaborate with the gastroenterology, anesthesiology and nursing communities to successfully integrate the SEDASYS System, and conduct two post-approval studies to monitor the use of the technology in actual clinical practice. During the session, we will review many of the specifics of this device and present an update on its current approval status.

Summary

Today there is a continued trend to expand the indications for ambulatory surgery. Because outpatient anesthesia is a break from our traditional training, we are constantly being confronted with the need for change in our clinical practice patterns. We have recognized that the needs of the surgical outpatient may be very different from the inpatient and are now trying to adapt our practice patterns to meet the psychologic and pharmacologic requirements of the compacted perioperative management the outpatient receives. This Refresher Course has focused on some of the controversial problems which we as practicing clinicians must deal with every day in our practice of ambulatory anesthesia for adult patients.


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REFERENCES

1. Chung F: Are discharge criteria changing? J Clin Anesth 1993; 5:64S-68S. 2. Chung F: Recovery pattern and home-readiness after ambulatory surgery. Anesth Analg 1995; 80:896-902. 3. Aldrete JA: J Perianes Nurs 1998; 13(3):148-55. 4. Apfelbaum JL, et al: Anesthesiology 2002; 97:66-74. 5. Sandberg et al: Anesthesiology 2012; 117:4: 772-779. 6. Meridy HW. Anesth Analg 1982, 61:921-6. 7. Natof HE. Ambulatory surgery: Patients with pre-existing medical problems. Ill Med J 1984; 166(2):101. 8. Chung F, Mezeu G, Tong D. BJA 1999, 83(2): 262-70. 9. Chung F, Mezei G. Anesth Analg 1999, 89(6): 1352-9. 10. Gross JB, et al. Anesthesiology 2006; 104(5):1081-1093. 11. Parsa P, et al. Anesth Analg 2004; 100:S-147. 12. Parker BM, et al. J Clin Anesth 2000; 12:350-6. 13. Harnett, et al. Anesthesiology 2010; 112:66 14. Fischer SP. Anesthesiology 1996; 85:190-206. 15. Ferschl MB, et al. Anesthesiology 103(4):855-859. 16. http://www.asahq.org/For-Members/Clinical-Information/Standards-Guidelines-and-Statements.aspx 17. Pambianco, et al: GI Endoscopy 2008;68: 542-547 18. http://www.asahq.org/publicationsAndServices/standards/37.pdf TABLE 1. DISCHARGE CRITERIA Awake, alert, oriented, responsive (or return to baseline) Minimal pain No active bleeding Vital signs stable (not likely to require pharmacologic intervention) Minimal nausea No vomiting If nondepolarizing neuromuscular blocking agent used, patient can perform sustained five second head lift Oxygen saturation of 94% on room air (three minutes or longer) OR return of oxygen saturation to baseline

or higher in order to be eligible to bypass Phase I recovery (PACU), the patient must meet ALL of the above criteria, and in the judgment of the anesthesiologist, be capable of transfer to the step-down unit, with appropriate care and facility for patient management at that location

Disclosure This speaker has indicated that he or she has no significant financial relationship with the manufacturer of a commercial product or provider of a commercial service that may be discussed in this presentation.


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Preoperative Evaluation of the Adult Outpatient

Barbara S. Gold, M.D. Minneapolis, Minnesota

Introduction Preoperative evaluation is a fundamental component of anesthetic delivery because it guides anesthetic management and postoperative care. This is especially true in the ambulatory surgical setting where preoperative evaluation also informs patient selection. Patient selection, in turn, is the cornerstone for safe and efficient ambulatory anesthesia care. In the outpatient setting the preoperative anesthesia assessment which exists in a variety of forms - is a key tool for both optimizing medical and administrative outcomes. Proactive identification and management of medical problems avoids last minute surprises that at best interrupt ambulatory surgery center patient flow and at worst contribute to adverse medical outcomes. This lecture will review: 1) the basic requirements for preoperative evaluation as determined by payers and regulators 2) models of preoperative evaluation and their merits and 3) preanesthetic evaluation of selected co-morbidities which are particularly relevant to the outpatient setting such as obesity, sleep apnea, cardiac disease, and insulin requiring diabetes.

Ground Rules The ground rules that govern US hospitals as set forth by the Joint Commission state that prior to any operative or other high risk procedure the patient receives a medical history and physical examination no more than 30 days prior to surgery. (Standard: RC.02.01.03, PC.01.02.03, EP 5) The American Society of Anesthesiologists has adopted standards (last amended in 2010) for preanesthesia care which is more specific http://www.asahq.org/For-Healthcare-Professionals/Standards-Guidelines-and-Statements.aspx; accessed 5/13) Basic Standards for Preanesthesia Care The anesthesiologist, before the delivery of anesthesia care, is responsible for: 1. Reviewing the available medical record.2. Interviewing and performing a focused examination of the patient to:

a. Discuss the medical history, including previous anesthetic experiences and medical therapy.b. Assess those aspects of the patients physical condition that might affect decisions regarding perioperativerisk and management.

3. Ordering and reviewing pertinent available tests and consultations as necessary for the delivery of anesthesia care.4. Ordering appropriate preoperative medications.5. Ensuring that consent has been obtained for the anesthesia care.6. Documenting in the chart that the above has been performed.

Furthermore the ASA Statement on Documentation (last amended in 2008) lists specific elements of the preanesthesia evaluation that should be recorded and further states that this is the responsibility of an anesthesiologist. (www.asahq.org/publicationsAndServices/sgstoc.htm, accessed 5/13) The content of this evaluation is to include medical history, anesthetic history, medications, appropriate physical exam including vital signs and documentation of airway assessment, review of objective diagnostic data and medical records, medical consultations when applicable, assignment of ASA physical status, formulation of anesthetic plan and documentation of risks and benefits of the plan including discharge issues when indicated. The Center for Medicare and Medicaid Services (CMS) issued Revised Hospital Anesthesia Services Interpretive Guidelines in December 2009 (with a clarification in January 2011) which reflect the ASA Statement for documenting preoperative assessment. What then is the best approach for satisfying these minimum requirements and professional society expectations? Clearly, the answer depends on the type of facility, patient population and procedures. Patient selection criteria, and hence evaluation paradigms, for a free-standing or office based practice will undoubtedly differ from a hospital


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based practice in a tertiary care center. In spite of these differences, there are some unifying guiding principles that apply to all settings. For starters, the basic requirements as outlined above need to be satisfied in a manner that is consistent and efficient. The goal is to determine who is fit for outpatient surgery and then to optimize those candidates. The extent and focus of the preanesthesia assessment is determined by the patients co-morbidities and type of surgical procedure. Secondly, a plethora of studies indicate that laboratory exams should be obtained for medical indication only and that routine testing is of no value, especially in the ambulatory setting. (1-3) However, the information gained from a thorough history and physical exam and clear communication with members of the perioperative team is of considerable benefit. Investigators of the Australian Incident Monitoring Study database identified poor airway assessment, communication problems, and inadequate preoperative evaluation as contributing factors in 197 preventable major adverse events (incidence 3.1%) including death and major morbidity. (4) While laboratory exams may not be useful, basic patient evaluation and communication of salient features are still essential. Over the past few decades, several models have been developed to facilitate preoperative communication, triaging, and medical evaluation. All of these models have their strengths and weaknesses, depending on the facility (free-standing center, office, hospital, etc.) and the patient population. Models for Systematic Preoperative Evaluation Patients can be evaluated on the day of surgery or seen in a preoperative evaluation clinic, or some hybrid version. The preferred model depends on patient demographics and type of facility. Patients evaluated the day of surgery have usually had a screening telephone interview with a preoperative nurse several days in advance of the procedure with anesthesiologist consultation as necessary. This method can be quite effective and efficient if relevant patient records (i.e., history and physical, laboratory values) are available at the time of the telephone screen, the nurses are well trained at interviewing, and have algorithms for seeking physician consultation. At the other end of the spectrum are preoperative evaluation clinics where patients are seen well in advance of surgery by an anesthesiologist and/or advanced practice nurse. These clinics are usually found in larger tertiary medical centers and face-to-face visits are reserved for patients with extensive co-morbidities. These clinics require institutional support and delineated organizational infrastructure. (5) Regardless of the method used, preoperative screening is cost effective and has the potential to yield substantial dividends by minimizing delays, cancellations, and opportunity costs. (6-8) While data for ambulatory surgery are limited, in a large urban medical center Ferschl and colleagues found same day surgery patients seen in the preoperative evaluation clinic had a cancellation rate of 8.4% as compared with a cancellation rate of 16% for same day patients who were not evaluated in clinic. Cancelations have significant negative financial impact, with estimates of over $1500/hr of lost revenue for every hour the OR sits idle (contribution margin). Data are beginning to emerge using preoperative assessment to predict future hospital costs. In the National Surgical Quality Improvement Program (NSQIP), 51 preoperative risk factors such as Cr > 1.2 or previous cardiac surgery, predicted post-operative cost variation due to complications and extended hospital stay. (9) The authors speculate that preoperative optimization of these risk factors would mitigate the occurrence of postoperative complications and hospital costs. This remains to be determined. Whether telephone screens or preoperative clinic visits are used, the model chosen for ambulatory anesthesia evaluation needs to emphasize patient selection using evidence-based algorithms developed by anesthesiologists and broadly shared with surgeons and their offices. This will permit effective triaging of patients and optimization of medical conditions preoperatively. For example, a patient with a drug-eluting cardiac stent placed within the year who abruptly discontinued clopidigrel would not be an appropriate candidate for elective surgery, irrespective of the venue. However, the same patient a year later may be perfectly appropriate for a hospital-based surgery center but not an office setting, depending on the procedure and other co-morbidities. Medical Evaluation This discussion will encompass medical co-morbidities that have considerable relevance to the outpatient setting due to the associated perioperative risks and dilemmas posed by discharging the patient within a few hours of surgery and anesthesia. Areas of focus include cardiac disease with an emphasis on stents and implantable cardiac rhythm devices, obesity and obstructive sleep apnea, and diabetes and perioperative glycemic control. Cardiac There is an abundance of data, guidelines and opinions to guide preoperative evaluation of cardiac risk. This section will focus on key studies and guidelines that are applicable to outpatients since the type of surgery is usually limited


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in scope, with minimal fluid shifts. However, most studies, which form the backbone of current guidelines, were extrapolated from (in) patients having extensive procedures. In guideline parlance, outpatient procedures are generally considered low risk however, lumping these procedures can be misleading (i.e., a cataract repair is not equivalent to a rigid bronchoscopy). Consequently, it becomes incumbent on the anesthesiologist to sort out which patients are at risk and require more extensive evaluation. Risk stratification methods are useful but they all have their limitations, namely they are often observational studies at a single institution. Nevertheless, common themes emerge. A landmark study of 4315 patients over 50 years having noncardiac elective surgery was used to identify independent risk factors, comprising the Revised Cardiac Risk Index (RCRI). (10) Although major cardiac complications were rare (2%) six independent risk factors were identified:

High risk surgery (intraperitoneal, intrathoracic, or suprainguinal vascular) History if ischemic heart disease History of congestive heart failure History of cerebrovascular disease Preoperative treatment with insulin Preoperative serum creatinine > 2.0 mg/dL

The authors specifically note that (T)he Index is of uncertain generalizability in lower-risk populations, such as patients who undergo minor procedures.. However, data specifically examining that population is lacking so this risk index is widely used. While risk indices can be quite useful, Reilly used a simple and practical - screening tool to predict perioperative risk, namely self-reported exercise tolerance. Poor exercise tolerance, such as the inability to walk 3 blocks or climb 2 flights of stairs (< 4 METS), is an independent predictor of serious perioperative complications (OR 1.94, CI 1.19-3.17). Moreover the likelihood of serious complications is inversely related to the number of blocks walked or flights of stairs climbed. (11) A decade later, in a single-center observational study, Kheterpal used NSQIP data to identify preoperative and intraoperative predictors of adverse cardiac events. (12) Their findings are consistent with findings from a decade earlier, with some modifications. Those independent predictors are:

Age > 68 yrs Active CHF BMI > 30 kg/m2 Emergency surgery Previous cardiac intervention Cerebrovascular disease Hypertension Operative duration > 3.8 hrs Administration of one or more units of PRBCs

All of the aforementioned predictors except for two (emergency surgery and administration of > 1 unit of PRBC) are commonly encountered in the ambulatory setting. On a related note, a supporting study by Correll and colleagues found that age > 65 was an independent predictor of preoperative electrocardiogram abnormalities. (13)

The findings from the aforementioned studies and many, many others led to the most recent (2007) American Heart Association/American College of Cardiology guidelines on perioperative evaluation for patients having noncardiac surgery. (14) (These guidelines were updated in 2009 with respect to perioperative beta-blockade.) There are some key points in these guidelines as they relate to ambulatory surgery. First, ambulatory surgery is considered as one entity and all ambulatory procedures are considered low risk with reported cardiac mortality < 1%. Secondly, in the absence of active cardiac conditions, interventions based on cardiovascular testing in stable patients would rarely result in a change in management and it would be appropriate to proceed with the planned surgery. In other words, in the absence of active cardiac conditions (unstable coronary syndromes, decompensated heart failure, significant arrhythmias, and severe valvular disease), additional interventions would rarely alter perioperative risk for low risk procedures. However, although additional testing may not be warranted (because it would rarely lead to a meaningful intervention), a complete and thorough history and physical exam which can probe the presence or absence of active cardiac conditions is essential. The AHA/ACC guidelines recognize that there are clinical risk factors (which are based on Lees Revised Cardiac Risk Index cited earlier). However, in the absence of active cardiac conditions, further action is rarely needed.


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Previous Coronary Interventions: Stents and Cardiac Rhythm Devices Stents Approximately two million patients per year in Western countries have cardiac stents placed and 90% of those stents are drug eluting stents which will require long term antiplatelet therapy. About 5% of stented patients will present for noncardiac surgery within the first year of stent placement. (15,16) The implications of cardiac stents and antiplatelet therapy on preoperative assessment requires a clinical understanding of the associated risks and well defined preoperative policies to guide patient selection and evaluation. With any coronary stent, there are risks, especially during the period of re-endothelialization. Until the period of re-endothelialization is complete, patients need to remain on dual antiplatelet therapy (i.e., aspirin and clopidigrel). Bare metal stents (BMS) are layered with endothelial cells after about 4-6 weeks. However, there is a risk that these stents are vulnerable to restenosis over time hence the development of drug eluting stents (DES). DES are coated with agents which impair cellular proliferation. This can prevent restenosis but also results in a longer period of time to stent re-endothelialization. During this period, patients must remain on dual antiplatelet therapy. Premature discontinuation of dual antiplatelet therapy, especially in the perioperative period, can be catastrophic due to stent thrombosis. (17-22) If noncardiac surgery is performed immediately after stent placement and without antiplatelet therapy, there is a 30% risk of perioperative MI and 20-40% of those are fatal. The risk of MI and death is 5-10 times higher than waiting the appropriate amount of time. Practice guidelines are unequivocal in stating that elective surgery be postponed until patients have completed an appropriate course of antiplatelet therapy. (14,18,22) The duration of antiplatelet therapy is currently estimated at minimum of 4 weeks for BMS and 12 months for DES, with aspirin continued indefinitely. However, some patients may be more prone to thrombosis and may need to remain on antiplatelet therapy for longer periods. Predictors of stent thrombosis are: bifurcated lesions, long stents, diabetes, renal failure and low ejection fractions. However, until more data are available, the practice guidelines are unequivocal. The ACC/AHA 2007 Perioperative Guidelines state: Elective procedures for which there is significant risk of perioperative or postoperative bleeding should be deferred until patients have completed an appropriate course of thienopyridine therapy (12 months after DES implantation if they are not at high risk of bleeding and a minimum of 1 month for bare-metal stent implantation).(14) Similarly, an ASA Practice Alert affirms the position of the ACC/AHA Perioperative Guidelines. (22) Since ambulatory surgery procedures are usually elective, patients need to defer surgery until 4-6 weeks after placement of a BMS and one year after DES. Aspirin should be continued in the perioperative period if at all possible. To avoid confusion and compromised patient care, it is extremely useful for surgery centers to have policies that reflect these guidelines.

Cardiac Rhythm Devices The perioperative assessment management of the adult surgical outpatient with a cardiac implantable electronic device (CIED) a pacemaker, an implantable defibrillator or both, is fairly common. This poses clinical and administrative challenges. (23-25) Indeed, perioperative management of these devices is the topic of an updated ASA Practice Advisory. (25) The indications for the CIED should be fully appreciated, as this often reflects significant underlying cardiac disease. (23) Permanent pacemakers are indicated for symptomatic third-degree heart block, type II second-degree heart block, sinus node dysfunction, recurrent neurally mediated syncope as well as some forms of cardiomyopathy. For example, biventricular pacemakers are considered in patients with significant heart failure (ejection fraction


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4. Assess CIED function Date of last interrogation and results Current setting Does the device capture when it paces? Effect of magnet on pacemaker function (ie, defaults to DOO at # bpm) Does CIED automatically reset to preoperative settings when a magnet is removed?

5. Likelihood of device interference

Will electromagnetic interference (EMI) be likely during the procedure? (EMI is unlikely if the device is < 10 years old and bipolar cautery is > 15 cm from device lead or generator)

Based on the likelihood of EMI, is reprogramming the CIED to asynchronous mode or disabling rate responsive function with a magnet or reprogramming indicated?

Should antitachyarrhythmia functions be suspended? (By whom?) Appropriate arrangements need to be made preoperatively so that the device can be reprogrammed (if necessary) in advance of the procedure and immediately after the procedure, without unduly inconveniencing patients or providers. If the device required reprogramming by the cardiology service/manufacturers representative preoperatively then original settings will need to be restored postoperatively and before discharge from PACU. Until those settings are restored, patients need to have cardiac monitoring with the capability to defibrillate immediately (i.e., defibrillator pads in place). Obesity Approximately 36% of the adult US population is obese and ~ 69% are overweight and obese (http://www.cdc.gov/nchs/fastats/overwt.htm, accessed 5/13). Obesity poses considerable perioperative challenges, and this is especially true in the outpatient setting where patients are expected to be discharged within a few hours after surgery. Associated co-morbidities such as obstructive sleep apnea and pulmonary dysfunction impact postoperative recovery/discharge and hence the patient selection process. A thorough understanding of the common obesity associated co-morbidities is useful to help formulate not only ambulatory anesthetic management but also patient selection criteria. Cardiovascular There is a direct and independent relationship between obesity and hypertension. (26-28) Furthermore, obese patients without documented hypertension are prone to occult diastolic dysfunction, probably secondary to increased circulating blood volume and chronic LV wall stress. (29) Systolic dysfunction associated with obesity is a later development, and is most often seen among obese patients with body mass index (BMI) > 40kg/m2 for > 10 years. (30) Cardiac function can be difficult to assess preoperatively due to diminished functional capacity. Consequently, non-invasive testing with appropriate modalities (such as stress echocardiography) may be required if patients have multiple risk factors or have limited functional capacity. (31,32) Reconciling the AHA/ACC cardiac evaluation and care algorithm for non-cardiac surgery in obese patients having ambulatory surgery requires clinical judgment. Indeed, this issue was highlighted in the recent advisory from the AHA regarding the cardiac evaluation of severely obese patients: (T)hese categorizatons (low, intermediate and vascular surgery) are used in the decision algorithm for further testing but it is unknown if obesity influences these categorizaitons. (33) Consequently, this AHA advisory recommends a preoperative ECG in severely obese patients (BMI > 40 kg/m2) with one risk factor for heart disease. If there are signs of CV disease (e.g., CAD, RVH consistent with pulmonary hypertension), additional workup based on functional capacity be pursued if it will change management.

Obesity and obstructive sleep apnea are associated with pulmonary hypertension which poses considerable perioperative risk. However, diagnostic criteria (such as signs of right heart failure) in the absence of an echocardiogram are vague, especially in the morbidly obese. The associated postoperative mortality in patients with pulmonary hypertension across several different inpatient procedures is estimated to be 7-10%. (35,36) Due to several factors, including intense intra and postoperative monitoring, these patients may not be candidates for the vast majority of ambulatory procedures and need to be carefully evaluated on a case by case basis. Obstructive Sleep Apnea (OSA) The prevalence of OSA in obese patients presenting for bariatric surgery is 71% -77%, depending on (BMI). (37) OSA is usually not a solitary diagnosis in an obese patient; associated co-morbidities include: hypertension and increased risk of cardiovascular disease (e.g., stroke and sudden death). (38-40) Sudden cardiac death in (non-surgical) obese patients is associated with a nocturnal pattern, which is distinctly different than in


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other populations. A review of polysomnograms and death certificates from 112 persons who experienced sudden cardiac death demonstrated that those with OSA had peak in sudden death from cardiac causes during sleeping hours (midnight to 6am). In contrast, those without OSA had peak incidence of sudden death after 6am. (41) In the perioperative setting, patients with OSA have an increased incidence of postoperative complications: Hwang measured home nocturnal desaturations preoperatively in 172 subjects. Patients with > 5 desaturations/hr had significantly higher rate of postop complications (15%) vs. those with < 5 events/hour (3%). Complications were primarily respiratory. (42) Chung evaluated 177 patients deemed at risk for OSA by various screening tools and then performed polysomnography. (43) Those with apnea-hypopnea index (AHI) >5 as confirmed by polysomnography had postoperative complication rate that was more than double those with AHI < 5 (27% vs. 12%). Discerning who actually has OSA is challenging, as the diagnostic gold standard is polysomnography, which many patients do not obtain. Diagnosis based on screening questionnaires is unreliable. A meta-analysis of clinical screening tests for OSA illustrates that it is possible to predict severe OSA with a high degree of accuracy. However, aside from severe OSA, false negative rates range from 14-38% which will miss a significant proportion of patients. (44) Nevertheless, simple screening methods have been developed for preoperative use including the STOP-BANG questionnaire which has a sensitivity from 84% (AHI>5) to 100% (AHI >30). Patients who answer yes to three or more items are considered to be at high risk of OSA. (43) Other similar validated tools incorporate upper airway anatomy to enhance predictive modeling. (45) STOP-BANG (Chung 2008)

1. Snoring Do you snore loudly (louder than talking or loud enough to be heard through closed doors)?

5. BMI BMI more than 35 kg/m2?

2. Tired Do you often feel tired, fatigued, or sleepy during daytime?

6. Age over 50 yr old?

3. Observed Has anyone observed you stop breathing during your sleep?

7. Neck circumference greater than 40 cm?

4. Blood pressure Do you have or are you being treated for high blood pressure?

8. Male gender?

A main concern for patients with OSA is their suitability for ambulatory surgery. Is it safe to send these patients home to an unmonitored setting after anesthesia and surgery? Data are scant since important determinants such as severity of OSA, type of anesthetic and type of procedure have not been individually examined. Instead, we have expert opinions extrapolated from inpatient setting and used as guide. The ASA Practice Guidelines for the Perioperative Management of Patients with OSA (2006) state that literature is insufficient to make recommendations and those guidelines are based on consultant opinion. (46) Moreover, the clinical screening tool suggested in ASA Guideline has not been clinically validated. The ASA Guidelines recommend that anesthesiologists determine whether a given surgical procedure and individual patient with (or at risk for) OSA is appropriate for outpatient setting. Factors to consider include: (1) severity of sleep apnea status (2) anatomical and physiologic abnormalities (3) status of coexisting diseases (4) nature of surgery (5) type of anesthesia (6) need for postoperative opioids (7) patient age (8) adequacy of postdischarge observation (9) capabilities of the outpatient facility Specifically in reference to outpatients, the ASA Guidelines recommends: These patients should not be discharged from the recovery area to an unmonitored setting (i.e., home or unmoniotored hospital bed) until they are no longer at risk for postoperative respiratory depression. The Guidelines also recommend observing patients while breathing room air in an unstimulated environment and note that this may require a longer ambulatory stay (i.e., 3 hours longer than non-OSA counterparts and median of 7h after last episode of airway obstruction or


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hypoxemia while breathing room air in an unstimulating environment). Practical application has been challenging because patients frequently do not have formal preoperative diagnosis of OSA and severity is difficult to estimate. Most likely, recommendations in this arena will continue to evolve as more relevant data become available. Obesity Hypoventilation Syndrome Obesity Hypoventilation Syndrome (OHS) exists in about 10-20% of patients with both obesity and OSA, and is characterized by the triad of obesity, daytime hypoventilation and sleep disordered breathing. Findings in patients with OHS include upper airway obstruction, restrictive chest physiology, blunted central respiratory drive, pulmonary hypertension and increased mortality. The mainstay of treatment is continuous positive airway pressure and weight loss. However, these patients are at higher risk for morbidity and mortality as compared to based who are eucapneic and obese. There are limited data on the perianesthetic management of these high risk patients, in any setting. (47) Diabetes Approximately 14% of US adults aged >20 years and ~27% of individuals >65years have diabetes or impaired fasting glucose. (http://www.cdc.gov, accessed 5/13) In order to evaluate potential end-organ damage and maintain metabolic homeostasis these patients require a focused assessment to a) gauge appropriateness for procedure on an outpatient basis, with a focus on potentially difficult airway in patients with long-standing Type I diabetes and b) guide preoperative fasting and insulin instructions. Cardiovascular disease is the major cause of morbidity and mortality amongst patients with diabetes, with the most common conditions being hypertension and dyslipidemias. The most recent American Diabetes Association guidelines (2012) recommend that patients with diabetes be treated to a blood pressure < 130 mm Hg systolic and < 80 mmHg diastolic. (48) Furthermore, it is recommended that all patients with diabetes have serum creatinine measured and cardiovascular risk factors such as dyslipidemia, hypertension, smoking, positive history of coronary disease and presence of mico- or macroalbuminemia assessed annually. This is part of routine health maintenance and is independent of surgical need. Further cardiac testing irrespective of the need for surgery - should be considered in diabetics with typical or atypical anginal symptoms or an abnormal resting ECG. (48) Patients with diabetes may be on complicated regimens to achieve glycemic goals in order to reduce the risk of micro and macrovascular complications. In addition to insulin and conventional oral hypoglycemic agents, treatment may include relatively new classes of gastrointestinal hormones namely incretins and amylin which impact glucose homeostasis. (49) In adults glycemic goals are: A1C < 7 % and preprandial glucose 70-130mg/dl and peak postprandial glucose < 180 mg/dl. (48) Due to concerns about perioperative hypoglycemia as delineated in the NICE-SUGAR study, perioperative glycemic goals as suggested by the ADA are in the range of 120 180 mg/dl. (48,52) To achieve those targets and simplify preoperative instructions, ambulatory surgery centers usually have protocols which address the type and quantity of insulin (and other hypoglycemic agents) to be administered preoperatively, recommendations for monitoring blood sugar preoperatively and treating hypoglycemia while adhering to NPO guidelines. A common feature in these protocols is to include a basal form of insulin on the day of surgery (usually as a fraction of the typical intermediate acting insulin or long acting insulin) and withhold oral hypoglycemic agents and incretins. (48-50) A basic understanding of the time course of commonly used insulins, as outlined below, is integral to developing effective preoperative instructions.

Insulin Comparison

Action Generic name Onset Peak Duration

Rapid Insulin Aspart 15 min 45-90 min 3-5 hrs

Short Regular Human Insulin 30 min 2.5-5 hrs 8 hrs

Intermediate NPH Insulin 1.5 hrs 4-12 hrs ~24 hrs

Long Insulin Glargine ~1 hr - up to 24 hrs

Long Insulin Detemir ~3 hrs ~6-8 hrs up to 24 hrs

Mixtures Insulin Aspart Protamine, Insulin Aspart 60 min 1-4 hrs up to 24 hrs

Mixtures Insulin NPH/ Regular, 70/30 ~30 min 2-12 hrs ~24 hrs


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Summary Outpatient evaluation is the basis for patient selection, which is fundamental for safe and efficient ambulatory anesthetic management. Models of evaluation include: assessment on the day of surgery, telephone triage, or preoperative clinic visit. Each model has its advantages, and adoption depends on the facility and patient demographics. Irrespective of the method, patients are evaluated with discharge planning in mind. Patients should be suitable for elective surgery with the expectation that they can be safely discharged home within a few hours of their procedure. Several co-morbidities affect this process and serve to refine patient assessments and selection criteria.

References 1) Chung F, Yuan H, et al. Elimination of preoperative testing in ambulatory surgery. Anesth Analg 2009; 108:467-75 2) Finegan B, et al Selective ordering of preoperative investigations by anesthesiologist reduces the number and cost of tests. Can J Anesth 2005; 52:575-80 3) Schein OD, et al. The value of routine preoperative medical testing before cataract surgery. N Engl J Med 2000; 342:168-75 4) Kluger M, Tham E, et al. Inadequate pre-operative evaluation and preparation. Anaesthesia 2000; 55:1173-1178 5) Bader AM, Correll DJ. Organizational infrastructure of the preoperative evaluation center. In, Preoperative Assessment and Management. 2nd edition. Editor: BobbieJean Sweitzer, M.D. Lippincott Williams & Wilkins/Wolters Kluwer. 2008 6) Correll D, Bader A, et al. Value of preoperative clinic visits in identifying issues with potential impact on operating room efficiency. Anesthesiology 2006; 105:1254-9 7) Ferschl M, Tung A, et al. Preoperative clinic visits reduce operating room cancellations and delays. Anesthesiology 2005; 103:855-9 8) Gibby G. How preoperative assessment programs can be justified financially to hospital administrators. Int Anesthesiol Clin. 2002; 40:17-30 9) Davenport D, Henderson W. et al. Preoperative risk factors and surgical complexity are more predictive of costs that postoperative complications. Annals of Surgery 2005; 242:463-471 10) Lee T, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation 1999; 100:1043-1049 11) Reilly D, et al. Self-reported exercise tolerance and the risk of serious perioperative complications Arch Intern Med 1999; 159:2185-2192 12) Kheterpal S, OReilly M, et al. Preoperative and Intraoperative predictors of cardiac adverse events after general, vascular, and urological surgery. Anesthesiology 2009; 110:58-66 13) Correll D, Hepner D. et al. Preoperative Electrocardiograms. Anesthesiology 2009; 110:1217-22 14) Fleisher L, Beckman, et al. ACC/AHA Guidelines on perioperative cardiovascular evaluation for noncardiac surgery. Circulation 2007; 116 15) Vicenzi M, Meislitzer T. et al. Coronary artery stenting and non-cardiac surgery. Br. J Anaesth 2006; 96:686-93 16) Spaulding C, et al. A pooled analysis of data comparing sirolimus-eluting stents with bare-metal stents. N Engl J Med 2007; 356:989-97 17) Chassot P-G, Delabays A, et al. Perioperative antiplatelet therapy. Br J Anaesth 2007; 99:316-28 18) Grimes C, Bonow R, et al. Prevention of premature discontinuation of dual antiplatelet therapy in patients with coronary artery stents. Circulation 2007; 115:813-818 19) Mehta S, Yusuf S. et al. PCI-Cure Study. Lancet 2001; 358:527-33 20) Rabbits J, Nuttall G. et al Cardiac risk of noncardiac surgery after percutaneous coronary intervention with durg-eluting stents. Anesthesiology 2008; 109:596-604 21) Nuttall G, Brown M. et al. Time and cardiac risk of surgery after bare-metal stent percutaneous coronary intervention. Anesthesiology 2008; 109:588-95 22) Practice alert for the perioperative management of patients with coronary artery stents. Anesthesiology 2009; 110:223 23) Myerberg R. Implantable cardioverter-debrillators after myocardial infarction. N Engl J Med 2008; 359:2245-53 24) Stone M, Apinis A. Current perioperative management of the patient with a cardiac rhythm management device. Semin Cardiothorac Vasc Anesth 2009; 13:31-43 25) Practice Advisory:Perioperative Management of Cardiac Implantable Electronic Devices: Pacemakers and Implantable Cardioverter-Defibrillators. Anesthesiology 2011; 114:24761 26)Kannel WB, Brand N, Skinner J, Dawber T, McNamara P. The relation of adiposity to blood pressure and development of hypertension Annals Int Med 1967; 67:48-59 27) Havlik R, Hubert H, et al. Weight and hypertension. Annals of Internal Medicine 1983; 98:855-859 28) Jones D, Kim J, Andrew M. Kim S. Hong Y. Body mass index and blood pressure in Korean men and women. J Hypertension 1994; 12:1433 29) Pascual M, Pascual D, Soria F, et al. Effects of isolated obesity on systolic and diastolic left ventricular function. Heart 2003; 89:1152-1156 30) Alpert M. Obesity cardiomyopathy: Pathophysiology and evolution of the clinical syndrome. Am J Medical Sciences 2001; 321:225-236 31) Gugliotti D, Grant P, et al. Challenges in cardiac risk assessment in bariatric surgery patients. Obes Surg 2008; 18:129-133 32) Kuruba R, et al. Preoperative assessment and perioperative care of patients undergoing bariatric surgery. Med Clin N Am 2007; 339-351 33) CV evaluation and management of severely obese patients undergoing surgery: A science advisory from the American Heart Association. Circulation 2009; 120;86-95 34) Subramaniam K, Yared J, Management of pulmonary hypertension in the operating room. Semin Cardiothorac Vasc Anesth 2007; 11:119 35) Lai H-C, et al. Severe pulmonary hypertension complicates postoperative outcome of non-cardiac surgery. Br J Anaesth 2007; 99:184-90 36) Ramadrishna G, Sprung J, et al. Impact of pulmonary hypertension on the outcomes of noncardiac surgery: Predictors for preoperative morbidity and mortality. J Am Coll Cardiol 2005; 45:1691-9 37) Lopez P, et al. Prevalence of sleep apnea in morbidly obese patients for weight loss surgery evaluation. Am Surg 2008; 74:834-38 38) Isono S. Obstructive sleep apnea of obese adults. Anesthesiology 2009; 110:908-21


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39) Lawate N, et al. Epidemiology, risk factors, and consequences of OSA and short sleep duration. Prog CV Dis 2009; 51:285-293 40) Yaggi H, Concata J, et al. Obstructive sleep apnea as a risk factor for stroke and death. N Engl J Med 2005; 353:2034-41 41) Gami A, Howard D, Olson E, Somers V. Day-night pattern of sudden death in obstructive sleep apnea. N Engl Med 2005; 352:1206-14 42) Hwang D, Shakir N, et al. Association of sleep-disordered breathing with postoperative complications. Chest 2008; 133:1128-1134 43) Chung F, Yegneswaran B, et al. Validation of the Berlin questionnaire and ASA checklist as screening tools for obstructive sleep apnea in surgical patients. Anesthesiology 2008; 108:822-30 44) Ramachandran S, Josephs L. A meta-analysis of clinical screening tests for obstructive sleep apnea. Anesthesiology 2009; 110:92839 45) Ramachandran S, et al . Derivation and validation of a simple perioperative sleep apnea prediction score. Anesth Analg 2010; 110:1007-15) 46) Practice guidelines for the perioperative management of patients with obstructive sleep apnea. Anesthesiology 2006; 104:108193 47) Chau EHL, et al Obesity Hypoventilation Syndrome: Review of Epidemiology, Pathophysiology, and Perioperative Considerations Anesthesiology 2012; 117:188205 48) Standards of Medical Care in Diabetes2012. Diabetes Care 2012; 35:S11-S63 49) Chen D, Lee S, et al. New therapeutic agents for diabetes mellitus: implications for anesthetic management. Anesth Analg 2009; 108:1803-10 50) Mooradian A, Bernbaum M. Narrative review: a rational approach to starting insulin therapy. Ann Intern Med 2006; 145:125-134 51) Clements S, Briathwaite S, et al. Management of diabetes and hyperglycemia in hospitals. Diabetes Care 2004; 27:553 52) Intensive versus conventional glucose control in critically ill patients. N Engl J Med 2009; 360:1283-97 Disclosure This speaker has indicated that he or she has no significant financial relationship with the manufacturer of a commercial product or provider of a commercial service that may be discussed in this presentation.


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Anesthesia for Outpatient Diagnostic or Therapeutic Radiology

Thomas W. Cutter, M.D. Chicago Illinois

Diagnostic radiology procedures are anatomic or functional, minimally to non-invasive, cause little pain or discomfort, and are most frequently performed without anesthesia services. When anesthesia care is requested, it is typically because of the patients unique physiological or psychological needs or desires. Therapeutic techniques are often more invasive and more likely to require an anesthesiologist because of the complexity of the procedure and the comorbidities and discomfort of the patient. All therapeutic procedures are to some degree interventional, but many diagnostic procedures are not, although an interventional radiologist may perform them. Conducting anesthetics in the radiology department can be challenging because of the patients comorbidities, the procedure, the anesthetic, the radiology equipment, and the environment.

Anesthetics can be one of three types: monitored anesthesia care (MAC), regional anesthesia, or general anesthesia. Selection depends on the procedure and the relative risks and benefits to the patient. Monitored anesthesia care, the least invasive anesthetic, is indicated when a procedure may nominally require deep sedation or increased monitoring.1 The anesthesiologist administers intravenous sedation and analgesia; the proceduralist may give an additional local anesthetic at the site. Monitored anesthesia care is a physician service that is distinct from moderate sedation because the anesthesia provider must be able to apply resources to support life and ensure patient comfort and safety during diagnosis or therapy.2

Diagnostic Radiology Iodinated contrast media is used in both diagnostic and interventional radiology and may cause adverse

(anaphylactoid) reactions or renal dysfunction. Adverse reactions involve direct cellular effects, including enzyme induction and activation of the complement, fibrinolytic, kinin, and other systems.3 Manifestations range from relatively benign itching to life-threatening cardiovascular or ventilatory collapse. Prophylaxis and treatment for the former include antihistamines and steroids, while advanced cardiac life support measures may be needed for the latter. Anaphylaxis is quite rare and is probably not a result of the iodine in the contrast material.4

Patient-specific risk factors for renal complications include chronic renal disease, diabetes mellitus, heart failure, older age, anemia, and left ventricular systolic dysfunction. Contrast-specific risk factors are high osmolarity, viscosity, volume, and ionic media. For patients with renal disease, diabetes, proteinuria, hypertension, gout, or congestive heart failure, serum creatinine levels should guide the radiologists administration of the contrast material. Adequate intravascular volume, bicarbonate, and low volumes of iso- or low-osmolar contrast are indicated. Diabetic patients with preexisting renal dysfunction who also take metformin have developed severe lactic acidosis after an iodinated contrast study. Thus, metformin should be discontinued at the time of or before the procedure, withheld for 48 hours subsequent to the procedure, and reinstituted only after renal function has been re-evaluated and found to be normal.5 Intravenous gadolinium for magnetic resonance imaging (MRI) contrast studies is not problematic during the anesthetic. Ultrasound contrast is achieved through the intravenous administration of echogenic microbubbles, which carry an FDA warning that patients with pulmonary hypertension or unstable cardiopulmonary conditions be closely monitored during and for at least 30 minutes after administration.6 Although barium is not an intravenous contrast, it should be mentioned because it may pose an aspiration risk after ingestion during deep sedation or general anesthesia.

Anatomic Imaging The ASA has issued a specific practice advisory 7 emphasizing a location or position for optimal patient

observation and vigilance during delivery of anesthesia in the MRI. The American College of Radiologists and the Joint Commission on the Accreditation of Healthcare Organizations have also established standards, guidelines, and recommendations for the MRI suite.8-10 Anesthesia equipment must conform to the criteria of the American Society for Testing and Materials and the Food and Drug Administration.

Patient monitoring and the administration of an anesthetic in the MRI suite are difficult because the anesthesia provider is physically separated from the patient during the study. The patient must be observed continually, either through a window into the scanner room or with a camera trained on the patient and a video monitor in the control booth. Vital signs must be monitored through a window or via a camera trained on a monitor in the scanner room or a slave monitor in the control room.

Monitor placement and the length and routing of leads, wires, and tubing should be considered to prevent entanglement or traction as the MRI tables moves. Coiling monitor wires (e.g., pulse oximeter,


212 Page 2 electrocardiogram) should be avoided because this can cause patient burns.11 Patient temperature should be monitored because it may increase from the heat of radiofrequency radiation within the magnetic field,12 or it may decrease by radiation, conduction, convection, and evaporation. Monitoring temperature intermittently instead of continuously may avoid the possibility of burns from the thermistor during long sessions or in critically ill patients.13

Medical emergencies must be anticipated and a plan in place to treat them. Although advanced cardiac life support may be instituted on a patient still in the scanner, prompt relocation outside the scanner room gives better access to the patient and is safer for the staff. If an emergency requires the magnet to be shut down quickly, (quenching)14 the liquid cryogen boils off rapidly and releases enormous amounts of helium vapor, so an evacuation plan must be in place. The scanner is noisy and there have been reports of patient hearing loss following MRI scan, so some form of ear protection is advisable, even for unconscious patients.15

Airway management must be scrupulous and conservative because of the distance and barriers between the anesthesiologist and the patient. It may be best to secure the airway outside of the scanner room and then transport the patient into the room.

Electromagnetic waves (X-rays) have been incorporated into a number of different imaging modalities, including static two-dimensional X-rays, dynamic two-dimensional X-rays (fluoroscopy) and three-dimensional computed tomography (CT). Major issues include the anesthesia providers radiation exposure and distance from the patient. The former is addressed by distance, lead, and personal dosimetry; the latter, by following protocols for monitoring similar to those in the MRI suite. The U.S. Occupational Safety and Health Administration has established limits for the exposure of individuals to radiation in restricted areas,16 and institutional guidelines should adhere to these standards. Radiology equipment (e.g., C-arm or CT aperture) can make airway management and access to the patient difficult, and the anesthesia equipment often adds to the difficulty of maneuvering in the suite, as can the encumbrance of a lead apron. The configuration of the table and other equipment means that patient positioning, especially lateral or prone, can be problematic.

For diagnostic fluoroscopy procedures, the contrast material may be ingested (e.g., barium swallow), administered per rectum (e.g., barium enema), or injected intravenously (e.g., intravenous pyelogram) or intrarterially (e.g., aortogram). Many procedures can be performed without anesthesia support, unless a patients comfort, comorbidities, or cooperation requires it. For example, diagnostic angiography is often performed with no or only light to moderate sedation and analgesia by cardiologists; percutaneous transhepatic cholangiography may be performed by a radiologist using the same regimen.

Computed tomography is an easily tolerated procedure for most patients and is relatively safe for personnel since the X-ray beam is tightly focused. Although studies are performed in a few seconds or minutes, they require a still patient, so cooperation must be assured either through patient reassurance or medications. Like diagnostic X-rays, diagnostic ultrasound imaging is noninvasive and easily tolerated. In the absence of invasive techniques, anesthesia support is not warranted; if it is indicated, no encompassing techniques or precautions are necessary.

Functional (Brain) Imaging Functional brain imaging reveals blood flow, metabolism, or electrical activity. Electrical activity is

represented by the electroencephalogram (EEG), which directly measures the electrical potential between two scalp electrodes. The EEG is spatially limited by the number of electrodes, a limitation that has been improved by high-density arrays of over 120 electrodes.17 Magnetoencephalography is a more sensitive technology that records local magnetic fields produced by neuronal electrical activity in the brain via extremely sensitive instruments such as superconducting quantum interference devices.

Other functional brain imaging techniques rely on the remarkably consistent relationship between regional changes in the cellular activity of the brain and changes in the blood flow and metabolism of the region.18 Blood flow is revealed by functional MRI (fMRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). A functional MRI distinguishes between the distinct magnetic resonance signals of oxygenated hemoglobin (diamagnetic) and deoxygenated hemoglobin (paramagnetic). A less common technique uses arterial spin labeling to magnetically alter the protons in the water molecules of the arterial blood in the neck and then identify them as they perfuse the brain. Functional MRI has been useful in determining the functional relationship between tumors and surrounding tissues.19

A PET scan involves injecting a radionuclide molecule that emits positrons which annihilate electrons and produce gamma rays that are then detected by the scanner. The amount of imaged tracer reflects blood flow and concomitant brain activity. Regional metabolic activity can be seen if the radionuclide molecule contains [F]-2-fluoro-deoxy-d-glucose (FDG),20 which concentrates in the more active areas. Positron emission tomography is often combined with CT or MRI to correlate anatomy with function. Like PET, SPECT detects gamma rays but the tracer material itself emits gamma radiation as it decays. More material indicates greater blood flow.

Metabolic activity also can be revealed through magnetic resonance spectroscopy, which detects signals specifically from hydrogen or phosphorous to determine the concentration of brain metabolites in tissue; greater levels indicate greater metabolic activity.


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These procedures are often performed on awake individuals, although occasionally a patients psychological or physical condition may require the use of sedation or general anesthesia. Administering anesthetic psychotropes may result in artifacts that disrupt the remarkably consistent relationship between regional changes in the cellular activity of the brain and changes in its circulation and metabolism. Isoflurane is associated with a relatively global reduction in brain glucose metabolism during PET with FDG.21 Propofol causes a larger absolute metabolic reduction, a greater suppression of cortical metabolism, and significantly less suppression of basal ganglia and midbrain metabolism.22 Propofol preferentially decreased cerebral blood flow in brain regions previously implicated in the regulation of arousal, performance of associative functions, and autonomic control and had more regional impact.23 Using fMRI, morphine demonstrates a regional effect, decreasing the signal in cortical areas as do propofol and midazolam, but activating endogenous analgesic regions such as the periaqueductal gray, the anterior cingulate gyrus (decreased signal), and hypothalamus (increased signal).24 Midazolam impacts fMRI by significantly altering the signal in the brains auditory and visual cortices.25 Mechanical maneuvers can also influence imaging outcomes, such as an increased mean airway pressure (e.g., continuous positive airway pressure) reducing the fMRI signal in the primary visual cortex.26

There are no strong recommendations for anesthetic technique for these diagnostic procedures. Indeed, functional brain imaging techniques such as PET and fMRI have been used to study the effects of general anesthesia on the brain, and a systematic baseline response to anesthetics has not yet been developed.27-29 If an anesthetic is required, the anesthesiologist should consider the anesthetics impact on cerebral blood flow, metabolism, and electrical activity and choose agents with minimal effect, combine agents to minimize their effects, and maintain steady-state anesthetic conditions during the study.

Therapeutic Radiology Therapeutic radiology has grown from relatively simple percutaneous procedures for aspiration/drainage to complex embolizations of arteriovenous malformations and the placement of arterial stents. It epitomizes the adage, There is no body structure that cannot be reached with a number 14 needle and a good strong arm, especially now that structures can be visualized in real time. Minor procedures such as biliary tube placement or exchange, tunneled catheter placement, vascular interventions, and other catheter insertions have been performed using moderate sedation, during which nurses, trained in critical care, monitor the patient and administer low-dose midazolam and fentanyl.30 Adverse events are few and minor without clinical impact.30 Less rather than more sedation is the rule in Europe, although general anesthesia is more common in Europe when anesthesia is utilized. In one East Coast academic center, MAC or general anesthesia was used for only 10% of cases for interventional radiology.31 As it increases in volume and complexity, interventional radiology is more often being performed in emergency settings and also includes more high-risk patients who cannot tolerate a more invasive (e.g., surgical) intervention, making an anesthesiologist necessary.32 The conditions for performing an anesthetic for therapeutic radiology procedures include those for diagnostic radiology: monitoring from afar, avoiding radiation exposure, working with radiology equipment and prohibiting ferrous materials in the MRI suites. The choice of anesthetic technique for interventional radiology is procedure specific with wide variations, depending on the patient and the skill sets of the interventionalist and associated personnel. The anesthetic presents more challenges because the procedure is invasive and the patient may have several comorbidities. The goal of a completely still patient, both for the success of the procedure and the safety of the patient, can sometimes be attained by sedation and analgesia administered either by the proceduralist or an anesthesia provider. If a predictable ventilatory pattern in the patient is desired, it can be achieved by the judicious administration of medications to a cooperative patient or by general anesthesia with controlled ventilation. Some particularly painful procedures (e.g., radiofrequency ablation of osteoid osteomas) require a subarachnoid block or general endotracheal intubation by an anesthesiologist .31 Other procedures associated with extreme fluid shifts (e.g., drainage of ascites fluid or blood loss during a uterine artery embolization) benefit from the presence of someone who is well versed in intravenous access. Some procedures may require anticoagulation and the means to measure its effects (e.g., activated coagulation time).

Fluoroscopy is the imaging modality typically used for endovascular stent placement. There is a significant procedural potential for complications and the patient may have been considered too sick for open surgery.33 Among the anesthetic techniques used for endovascular aortic repair are general, epidural, combined epidural/spinal, 34 spinal, and continuous spinal.35 Even when performed under MAC, one must be prepared for significant blood loss and invasive monitoring.36 Mild hypotension, and an immobile patient are important when deploying the stent. Spinal cord injury may be decreased by limiting hypotension, monitoring evoked potentials and cerebrospinal fluid (CSF) pressure, and measuring CSF proteins (S100 ) during thoracic aneurysm stenting.37 An intrathecal drain may be beneficial for thoracic aneurysm procedures,38 but it may also lead to catheter-related complications.39 Carotid artery stenting may be superior to traditional carotid endarterectomy in patients who are at overall increased surgical risk.40 Aspirin and clopidrogel are often administered before the procedure and heparin is


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given intraoperatively while activated clotting time is monitored. Stenting may be performed in a patient under MAC, with close attention paid to central nervous system changes and bradycardia,33 or under general anesthesia. General anesthesia depresses barorecepter reflex sensitivity and induces hemodynamic stability, potentially decreasing complications.41

Stenting to improve blood flow through iliac, popliteal, subclavian, or renal arteries does not mandate the presence of an anesthesiologist 42 unless the patients comorbidities require it. Stenting of venous outflow has been used for chronic nonmalignant or malignant obstruction of the femoroiliocaval vein,43 and patients with neoplastic superior vena cava syndrome have received palliative stents without sedation. 44

A transjugular intrahepatic portosystemic shunt relieves portal hypertension by using an expandable metallic stent to create an artificial channel between the branches of the portal and hepatic veins. It is typically performed under MAC or general anesthesia,45 with the patients mental status, ability to tolerate the procedure without moving, overall hemodynamic status, and ease of airway management dictating the type of anesthesia. Significant comorbidities can include pathological shunting in vascular beds, leading to increased cardiac output and heart failure. Ascites, pleural effusions, intrapulmonary shunting, pulmonary hypertension, hepatorenal syndrome, encephalopathy, and coagulopathies are common in these patie

ASA 2013

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