A Critique of Anesthesia Technology

D. John Doyle MD PhDCleveland Clinic Foundation

May 2004

OUTLINE

1. Introduction

2. Low-tech vs. high-tech monitoring

3. Survey of potential problems

4. Problems not easily detected without high-tech monitors

5. Evidence that high-tech monitoring is helpful

INTRODUCTION

Anesthesia technology, despite clear overall clinical advantages, carries with it an unexpected burden that has now become quite troublesome.

THE ESSENTIAL ARGUMENT

PREMISE: The easier it is for the anesthesiologist to figure out what's going on when the patient is crashing, the better it is for the patient.

FACT: High-tech monitoring often helps sort-things out when there is a problem with the patient. FACT: High-tech monitoring is expensive in several ways and involves a cognitive (mental) load on the anesthesiologist

LOW-TECH MONITORS

Look (colour, respiratory pattern ...) Listen (air entry, heart sounds ...) Feel (pulse, forehead, reservoir bag ...) Blood Pressure Temperature Nerve Stimulator Urometer

HIGH-TECH MONITORS*

Electrocardiogram(± ST segment)( ± rhythm)

Pulse oximeter Capnograph Anaesthetic Agent Analyzer Evoked Potentials

*Microcomputer-based in most cases

The Argument Against High-Technology in

Anaesthesia

COMMON CRITICISMS OF HIGH-TECH MONITORING

1. "It leads anesthesiologists to look at the monitors, not at the patient."

2. "I don't need all these gizmos to know how my patient is doing."

3. "They complicate delivery of anesthesia."

4. "It's too expensive."

OBJECTIONS TO HIGH-TECH MONITORING

... a look at some complaints and observations

.... There are some who feel that technology in anesthesiology is a contributing factor in some of the medical liability problems."

[Capps RT. 1983 President's Annual Report. ASA NEWSLETTER 1982; 46(12): 2-8.]

REFERRING TO CAPNOGRAPHIC MONITORING ....

"In almost 30 years of anesthesia practice, I have yet to encounter a case in which the outcome could have been changed by the presence of such a monitor."[Peterson AW. Standards for monitoring during anesthesia at Harvard (letter). JAMA 1987; 257(1): 25 - 26.]

'We should recognize and acknowledge that the true value of monitoring has not been validated and slavish obedience to sets of standards, wheteher imposed by professional societies or legal bodies, is neither in the interests of anaesthetists nor their patients."[ Zarab JSM (letter). Today's Anaesthetist 1991; 6:150.]

POTENTIAL PROBLEMS WITH HIGH-TECH MONITORING

Expense Inconvenience Lack of alarm reliability Equipment clutter Learning curve / training

Concerns about Anesthesia Technology

• Acquisition Cost• Maintenance Costs• Calibration• Storage and

transportation

• Ergonomics• Need for isolated

electrical power• Sensitivity / specificity• Clinical Value

Gourmet Baloney in Anesthesia?

• Mallampati Criteria

• Combined CSF/epidural techniques

• Wedge Pressure Measurements

• PACU Discharge Scoring Systems• CSF Drainage for Aortic Reconstructive Surgery

• Ultra Short Acting Narcotics

• Heart Rate Variability

Electroencephalography

• Raw EEG

• Compressed Spectral Arrays

• Bispectral Analysis

• Effects depend strongly on agents used (e.g., narcotic versus vapor)

Electroencephalography

• Cardiopulmonary bypass

• Carotid vascular surgery

• Neurological surgery

• Comatose patient

• Head injured patient

Monitoring that has “passed on”

• Ballistocardiography

• Vector cardiography

• Systolic time intervals

• Galvanic skin response

• Classical electroencephalography

• Classical photoplethysmography• Video stethoscope NEVER COMMERCIALIZED

Ideal Monitor Properties

• Inexpensive

• Reliable

• No complications

• Tells you something important

• Demonstrated clinical utility

ERGONOMICS

• Science of “Human Factors”

• Concerned with– man/machine interfacing– control layout visual displays– labels– human error– classical and knowledge-based alarms

Software

• All modern monitors use software

• Software often has “bugs” (e.g., leading to system crashes)

• Software sometimes has fatal defects

• Trivial software changes sometimes lead to completely unexpected ( and sometimes deadly) side effects.

Software and Ergonomics

distinguish

modern from older monitors

PA Catheter Controversy• JAMA 1996 Review

– Article JAMA 1996; 276:889-897

(SUPPORT study)– Editorial JAMA 1996; 276:916-918

(Call for moratorium in PA use)

• ASA Practice Guidelines– Anesthesiology 1993; 78:380-384

• Anesthesia and Analgesia Editorial– Anesthesia and Analgesia 1997; 84:1-4

PA Catheter Controversy

• Selection Criteria

• Goal Directed Therapy

• Benefits

• Measurement Error

• Complications

CHESTStatement on Pulmonary Artery

Flotation Catheters (PACs)• No indication for a moratorium on the use of the PA

catheter at this time• Well-designed clinical trials are still needed• Decisions about PAC insertion should be based on

clinical risks and benefits for each individual patient• Informed consent prior to PAC insertion is desirable• Physicians placing PACs should be skilled in

placement, troubleshooting, and interpretation

Anesthesia Technology QA

• Who does it?

• Who pays for it?

• Any standard or national guidelines?

• What are the hazards of poor QA?

In Favor of High-Tech Patient Monitoring

We rely heavily on high-technology monitoring for a very good reason:

Despite its problems, advances inhigh-tech monitoring methods such as capnography is saving lives and probably even saving money.

“We rely heavily on high-technology monitoring for a very good reason”

Evidence to support this comes from anecdotal cases and informal surveys, as well as from formal efforts such as the ASA Closed Claims Project, retrospective hospital studies, and even prospective, randomized controlled-outcome studies.

Keeping an Eye on the Patient ... the price of safety is eternal vigilance

Good clinicians do not ignore their patients and focus only on the monitors just because they are using high-tech machines. However, there are many clinical situations where it is not possible to see much of the patients (e.g. neurosurgery). In many ORs where patients arms are tucked in, all an anesthetist gets to see is a head, neck and upper chest. This view can provide useful clinical data (erythema, edema, bleeding, urticaria, subcutaneous erythema, hematomas, purpura, ecchymoses, etc.) that is an adjunct to electronically acquired data. A precordial or esophageal stethoscope also offers much information of potential clinical value. Rhythm disturbances can be noted and airway-related noise changes (e.g. wheezing) may be detected. However, both the ECG and the pulse oximeter provide visual and audio data for rhythm monitoring, making the stethoscope principally useful for detecting wheezes.

There are many clinical problems which are not readily detectable without high-tech monitors.

In particular, capnography is the only fully reliable routinely used method to detect esophageal intubation, a common cause of anesthetic-related deaths in the pre-capnography era.

* hypoxic accidents* "wrong gas" incidents* esophageal intubation* expiration valve failures* vaporizer overdoses* air emboli

These problems are not easily detected by clinical means alone.

EVIDENCE THAT HIGH-TECH MONITORING IS HELPFUL IN IMPROVING PATIENT SAFETY IN ANAESTHESIA

anecdotal cases informal surveys ASA Closed Claims Project retrospective studies prospective, randomized controlled-outcome studies

Studies demonstrating the value of high-tech monitoring...retrospective and prospective studies

1. In the ASA Closed Claims Project, nearly one-third of the negative outcomes (primarily respiratory) leading to the claims could have been prevented by the use of additional monitors. (Anesthesiology 1989; 71: 54; 1990: 72: 828)

2. In a retrospective study of case files from 1976 to 1988, 7 of 11 intraoperative events might have been prevented by the use of pulse oximetry and capnography (Anesthesiology 1989; 70: 572).

3. In a randomized prospective trial of pulse oximetry, there was a 19-fold increase in diagnosed hypoxemia in patients with a pulse oximeter as opposed to those patients who were monitored clinically for hypoxemia (Anesthesiology 1991; 75: A867 and A1057).

4. In another study, it was found that the universal use of pulse oximeters in the OR was associated with a decrease in unanticipated admissions of patients to an ICU to rule out an MI (Anesth Analg 1992; 74:181).

5. In a study on unexpected cardiac arrest during spinal anaesthesia, strong evidence was found to infer the presence of respiratory insufficiency even though the patients were closely watched (Anesthesiology 1988; 68: 5).

TransEsophageal Echocardiography

POTENTIAL APPLICATIONS

• Aortic reconstructive surgery

• Cardiomyopathies

• Aortic, mitral or other valve surgery

• Regional and global cardiac performance

TransEsophageal Echocardiography

• Six month minimal training period?

• Certification program

• Reimbursement issues

• Not entirely complication free

• Clear utilization guidelines are needed

RESPIRATORY MONITORING

One clinical realm where high-tech monitoring is clinically useful is in respiratory monitoring, especially in detecting unrecognized esophageal intubation.

RECOGNITION OFTRACHEAL INTUBATION

Chest movement POOR Auscultation POOR Reservoir Bag Compliance POOR Tube Condensation POOR Chest Radiography IMPRACTICAL Capnography Fiberoptic Bronchoscopy Direct visualization (seeing ETT go thru cords)

UNRECOGNIZED ESOPHAGEAL INTUBATION*

Of 27 cardiac arrests over a 15 year period which were attributed solely to anesthesia, 4 were due to unrecognized esophageal intubation (JAMA 253: 2373 - 2377).

7 of 192 complications resulting in cardiac arrest, brain damage, or death were secondary to esophageal intubation (Int Anes Clin 1984, pp. 43 - 59).

50 cases of accidental esophageal intubation from 1970 to 1977 reported by the Medical Defense Union of the U.K. (CASJ 26: 472 - 478).

A review of anaesthesia related liability claims in the U.K. from 1977 to 1982, listed esophageal intubation as a main cause of accidents leading to death or neurologic damage (Int Anes Clin 1984, pp. 73 - 89).

*Pre-capnography era

ASA CLOSED CLAIMS PROJECT

(Tinker et al. Anesthesiology 1989; 71: 541, Caplan et al. Anesthesiology 1990; 72: 828)

Nearly one-third of the negative outcomes leading to the claims could have been prevented by the use of additional monitors.

Respiratory events were the largest single class of injury.

EICHORN STUDY

(Eichorn JH. Prevention of intraoperative accidents and related severe injury through safety monitoring. Anesthesiology 1989; 70: 572.)

Retrospective study of case files from 1976 to 1988.

7 of 11 intraoperative accidents might have been prevented by the use of pulse oximetry and capnography.

Pulse Oximetry and UnanticipatedICU Admissions

Cullen DJ et al. Anesth Analg 1992; 74: 181.

Universal use of pulse oximeters in their operating rooms was associated with a decrease in unanticipated admissions of patients to an intensive care unit to rule out myocardial infarction.

RANDOMIZED PROSPECTIVE TRIALS

(Moller Anesthesiology 1991; 75: A1057Moller Anesthesiology 1991; 75: A867)

Design Control group - no pulse oximetry Experimental group - pulse oximetry used

Results 19-fold increase in diagnosed hypoxemia in the pulse oximetry group Less myocardial ischemia in pulse oximetry group

PROBLEMS IN VIGILANCE

1. Boredom

2. Occupied with another task(e.g. hanging blood, preparing drugs).

3. Fatigue

UNEXPECTED CARDIAC ARRESTDURING SPINAL ANESTHESIA

(Caplan et al. Anesthesiology 1988; 68: 5 - 11.)

Reviewed the antecedents to sudden cardiac arrest in 14 healthy patients who had received spinal anaesthesia.

Found strong evidence to infer the presence of unappreciated respiratory insufficiency even though the patients were being "closely watched".

Studies on Auscultation

... auscultation may not be all its cracked up to be

Cooper and Cullen (J Clin Monit 1990; 6: 271) carried out a study on how well anesthesiologists listened to an esophageal stethoscope. In 32 patients, 320 random stethoscope occlusions were carried out; the mean time to detection was 34 seconds (SD = 59). This suggests that the esophageal stethoscope may be of limited value for real-time rhythm monitoring.

Mizutani et al (J Clin Monit 1991; 7: 232) compared the acoustics of esophageal and tracheal ETT placement and concluded that "one cannot distinguish between the two types of intubation by means of auscultation".

ESOPHAGEAL STETHOSCOPE OCCLUSION EXPERIMENT

Cooper and Cullen 1990 (J Clin Monit 6: 271)

Routine anesthesia with esophageal stethoscope in use

Anesthesiologist aware of study and gave informed consent

Computer-guided device artificially, silently, and at random time intervals, occluded the stethoscope tubing

ESOPHAGEAL STETHOSCOPE OCCLUSION EXPERIMENT (Cont'd)

Anesthesiologist noted when they perceived the absence of stethoscope sounds

32 patients/320 occlusions

Time between occlusion and detection (mean ± SD): 34 ± 59 seconds

"Esophageal stethoscope has some definite limitations"

The End