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ANESTHESIA 101

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

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ANESTHESIA 101

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  1. ANESTHESIA 101 Desiree Persaud MD FRCPC Assistant professor University of Ottawa Resident Coordinator Dept of Anesthesiology The Ottawa Hospital Civic Campus

  2. Overview • History • Facts/Fiction • Case presentations

  3. 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

  4. Anesthesia • 1846: ether anesthesia

  5. Definition Awake Unconscious • 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

  6. 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

  7. General Anesthesia 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. 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

  10. Adjuncts - continued • Muscle relaxants • Succinyl choline, rocuronium • Block NMJ • Skeletal muscle paralysis Problems: • Inability to reverse • Awareness

  11. Adjuncts – cont. • Induction agents: • Propofol, pentothal, ketamine • Narcotics: • Fentanyl, remifentanil • Non-narcotic analgesics: • Ketorolac, lidocaine, magnesium • Anti-emetics • Dexamthasone, ondansetron

  12. 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

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

  14. 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

  15. 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

  16. 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

  17. Appendectomy • 4 cases scenarios • Patients/pathology come in different packages:

  18. 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)

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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,

  25. 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

  26. 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

  27. 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

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

  29. 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

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

  31. 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

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