ANESTHESIA 101 Surgery Core program Nov 4, 2008

1. ANESTHESIA 101Surgery Core program Nov 4, 2008 Desiree Persaud MD FRCPC Associate Professor University of Ottawa Regional Anesthesia Director, The Ottawa Hospital Resident Coordinator, Dept of Anesthesiology The Ottawa Hospital Civic/Riverside Campus

2. Overview • History • Anesthetic principles • Case presentations

3. Surgery prior to Anesthesia • The last resort • Medieval torture chamber – restraints/gags • Physical assault: blow to the jaw • Ice: freezing/conduction anesthesia • Plants: marijuana, belladonna • Alcohol, opium • Hypnosis, distraction

4. Anesthesia • 1846: ether anesthesia

5. Who are we and what do we do? • Perioperative acute care physicians • Perioperative pain management experts • 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 • Interventional anesthesiology – TEE, TTE, U/S guided nerve blocks/line placement, flouroscopic chronic pain blocks,

6. Definition Awake Unconscious • Anesthesia: Greek: 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

7. General Anesthesia Awake Unconscious xNot an On/Off Switch • Suppression of consciousness with profound systemic effects • Lipid theory • Protein theory

8. General Anesthesia - continued XNot “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

9. 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

10. Spinal • Pros: • Quick onset • Dense surgical anesthesia • Cons: • Limited duration - < 4 hours • Limited cephaled spread • Rapid sympathectomy • Limited post op analgesia

11. Epidural • Catheter placed – can extend duration of block • Most often used in combo with GA • Post-op analgesia • Less need for systemic narcotic • Bowel function preserved

12. Peripheral Nerve blocks • Mainly for orthopedic and vascular surgery • Unlike neuraxial—virtually no systemic side effects • Provides site specific post-op analgesia

13. Patients/pathology come in different packages: 4 case presentations: same surgical pathology BUT 4 very different anesthetic plans!!

14. Case 1 • 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)

15. Pre-anesthetic assessment • Assess level of hydration: • General anesthesia will depress CVS reflexes • Potential for hypotension • Assess Airway – aspiration risk • Assess for other comorbid conditions • Resp/CVS

16. 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

17. Is an appendix always an appendix? • Case 2: 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

18. 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

19. Change approach to laparoscopic appendectomy?Does it matter? • Case 3: Laparoscopic approach • 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

20. 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,

21. 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

22. Case 4: 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

23. 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

24. Emergence • Reversal of anesthesia: just as risky as induction • Patients: responsive, protect A/W • Stable: BP/temp • Adequate reversal

25. Post-operative care • Monitoring: • LOC/hemodynamic/O2saturation • Pain control • Nausea/Vomiting • Ambulation/movement

26. 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

27. Take home messages • 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 • Communication is KEY