ANESTHESIA 101 Desiree Persaud MD FRCPC Assistant professor University of Ottawa Resident...
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Transcript of ANESTHESIA 101 Desiree Persaud MD FRCPC Assistant professor University of Ottawa Resident...
ANESTHESIA 101
Desiree Persaud MD FRCPC
Assistant professor University of Ottawa
Resident Coordinator
Dept of Anesthesiology
The Ottawa Hospital Civic Campus
Overview History Facts/Fiction Case presentations
Surgery prior to Anesthesia The last resort Medieval torture chamber – restraints/gags Physical assault: blow to the jaw Plants: marijuana, belladonna Hypnosis, distraction Alcohol, opium
Anesthesia 1846: ether anesthesia
Definition Anesthesia: No sensation Types: Alone or in combo
General anesthesia Neuraxial anesthesia
Spinals and Epidurals – lower extremity/bowel surgery
Peripheral Nerve Blocks Paravertebral – breast surgery Femoral - knee replacement/muscle biopsies
Awake Unconscious
Anesthetic principles Perioperative acute care physicians Direct manipulation of physiology Intricate knowledge of pharmacology Expert laryngoscopist/backup A/W methods Regional/invasive line placement/anatomy knowledge Equipment: ventilators/monitors/gas delivery systems
General Anesthesia
x Not an On/Off Switch
Suppression of consciousness with profound systemic effects Lipid theory Protein theory
General Anesthesia - continuedX Not “going to sleep” Is a chemically induced “coma”
Direct CNS system depression Lack of A/W reflexes Depression of the respiratory centres Direct CVS depression Multiple pharmacologic effects influencing every
system – gut/liver/renal/endocrine/neuromuscular
General Anesthesia - adjuncts Volatile agent : the “gas”
Potent CVS depressant No analgesic effects
Nitrous Oxide: Not very potent Distends spaces – eg bowel
Narcotics Potent RESP depressant PONV
Adjuncts - continued Muscle relaxants
Succinyl choline, rocuronium Block NMJ Skeletal muscle paralysis
Problems: Inability to reverse Awareness
Adjuncts – cont. Induction agents:
Propofol, pentothal, ketamine Narcotics:
Fentanyl, remifentanil Non-narcotic analgesics:
Ketorolac, lidocaine, magnesium Anti-emetics
Dexamthasone, ondansetron
Neuraxial anesthesia Neuraxis = spinal cord Benefits:
No direct CNS, Resp, CVS depression No need for muscle relaxants Provides analgesia
Problems: SNS blockade – hypotension Spinal hematoma - anticoagulants
Spinal
Pros: Quick on set Dense surgical anesthesia
Cons: Limited duration - < 4 hours Limited cephaled spread Rapid sympathectomy Limited post op analgesia
Epidural Similar to spinals Longer onset Catheter placed – can extend duration of block Most often used in combo with GA Post-op analgesia
Superior: bowel function preserved Less need for systemic narcotic
Peripheral Nerve blocks Mainly for orthopedic and vascular surgery Unlike neuraxial—virtually no systemic side effects Provides superior post-op analgesia Takes time for placement and onset
Pre-assessment: consults Pts with Hx of difficult intubation Personal/Family Hx of anesthesia problems Pts with uncontrolled resp disease Pts with unstable coronary disease Endocrinopathies – pheochromocytoma Pts on anticoagulants: plavix/ticlid/LMWH
Appendectomy 4 cases scenarios Patients/pathology come in different
packages:
Cases 25 yr old male for open appendectomy Issues:
Emergency case Acute abdomen – risk perforation/sepsis “full stomach” – aspiration risk Dehydration – Nausea and Vomiting General (or neuraxial anesthesia)
Pre-anesthetic assessment Assess level of hydration:
General anesthesia will depress CVS reflexes Potential for hypotension
Assess for other comorbid conditions Resp/CVS
Assess Airway – aspiration risk
Intra-op management Functioning IV – volume replacement Optimal airway positioning Rapid intubation with muscle relaxant and cricoid
pressure Narcotic, IV induction agent, relaxant
Maintain with volatile/narcotics Extubate reversed and awake
Is an appendix always an appendix? Case: Change age to 75 yr old male Additional issues:
Compensatory mechanisms less More likely to have resp/CVS comorbidities More “sensitive” to CNS depressants Less tolerance of physiologic stressors
Intra-operative management IV fluids – pre-op fluid hydration more careful and
essential Monitors include: ST seg monitoring Slow, titrated induction Minimize volatile – predispose to hypotension Great risk of hypotension while the surgeon is
scrubbing!!! Non-compliant vasculature – rapid swings of BP Delayed emergence possible
Change approach to laparoscopic appendectomy?
Does it matter? Laparoscopy
Trocar: vessel/viscous perforation Relaxation, large IV
Pneumoperitoneum: Restrictive resp defect – high PAW, atelectasis Vagal efferent relfex Reduction in preload – hypotension Incr gastric pressure – aspiration risk S/C emphysema pneumothorax
Laparoscopy considerations - cont. Carbon dioxide
SNS stimulant: BP, HR Pulmonary V/C – predispose to PH Cerebral V/D –ICP Acidosis – K, enzyme dysfunction Embolus – CV Collapse
Positioning: loss of Airway, lines,
Intraoperative management Fluid hydration key—reduction in preload Trocar insertion – must ensure patient does not move:
COMMUNICATE Difficulty with trocar insertion
COMMUNICATE Avoid too high intrabdominal pressures Avoid too steep trendelenburg
Change patient: morbidly obese for laparoscopic appendectomy BMI > 35 CNS: sensitive to depressants/apnea A/W: obstruction/difficult to secure Resp: restrictive defect/ PH CVS: HP, LVH, CAD GI: reflux Endo: DM
Intraoperative management Meticulous airway positioning Prone to desaturation Trendelenburg poorly tolerated – ventilatory
difficulty: atelectasis-shunting Pre-existing PH: high CO2/low O2
Delayed emergence Prolonged PACU/overnight stay
Emergence Reversal of anesthesia: just as risky as induction Patients: responsive, protect A/W Stable: BP/temp Adequate reversal
Why are they so “slow”? Pre-operative assessment Difficult IV access – MO, cancer pt Epidural/Spinal placement Difficult A/W: positioning/adjuncts/awake intubation:
topicalizaton Hemodynamic instability: BP, HR, rhythm Line placement: CVP/A. line Delayed Emergence: excess
narcotics/relaxant/hypothermia
Post-operative care Monitoring:
LOC/hemodynamic/sats Pain control Nausea/Vomiting Ambulation/movement
Take home message
Anesthetics are tailored to both the patient and procedure Patients and procedures come in different packages General anesthesia is not an on/off switch General anesthesia is not going to “sleep” Multiple dynamic physiologic effects Time to induce/maintain/emerg Regional techniques have multiple advantages Communication is KEY