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OMSB Anesthesia (OEA) study materials
OMSB Anesthesia (OEA) study resources

OMSB Anesthesia (OEA): Anesthesia - Perioperative Decision-Making, Dosing and Crisis Protocols (OMSB OEA)

OMSB Anesthesia (OEA) · Work through your exam, one topic at a time.

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Anesthesia - Perioperative Decision-Making, Dosing and Crisis Protocols (OMSB OEA)

What this domain tests

The OEA anaesthesia paper samples the whole perioperative pathway: preoperative risk stratification, airway planning, pharmacology and dose precision, intraoperative monitoring, obstetric and paediatric variants, and the management of perioperative crises. Items are usually short vignettes with one best answer; marks are lost on sequence, thresholds and exact doses rather than on broad concepts.

Rules and numbers to own

  • Elective fasting: clear fluids 2 h, breast milk 4 h, infant formula or light meal 6 h, fatty/fried meal 8 h.
  • Difficult airway: declare a plan before inducing, limit optimised attempts (three), keep oxygenating with a second-generation supraglottic device, then move to front-of-neck access.
  • Volatile MAC in oxygen: sevoflurane ~2.0, isoflurane ~1.15, desflurane ~6.0, nitrous oxide ~105. MACs are additive (0.5 MAC volatile + 0.5 MAC N2O = 1 MAC).
  • Local anaesthetic ceilings: bupivacaine 2 mg/kg plain (2.5 mg/kg with adrenaline); lidocaine 4.5 mg/kg (7 mg/kg with adrenaline).
  • Malignant hyperthermia: stop triggers, 100% O2, dantrolene 2.5 mg/kg IV repeated to 10 mg/kg, treat hyperkalaemia and acidosis.
  • LAST: stop injection, secure airway with 100% O2, benzodiazepine for seizures, 20% lipid emulsion 1.5 mL/kg bolus then 0.25 mL/kg/min.

Worked example

A 70 kg man receives 30 mL of 0.5% bupivacaine for an interscalene block: 150 mg, about 2.1 mg/kg - above the 2 mg/kg plain ceiling. He becomes agitated, then seizes. Reasoning: (1) diagnose LAST clinically, do not wait for plasma levels; (2) stop injecting immediately; (3) lipid bolus 1.5 x 70 = 105 mL, then infusion 0.25 x 70 = 17.5 mL/min; (4) avoid large adrenaline boluses and avoid lidocaine as the antiarrhythmic.

Traps

Treating LAST with a large adrenaline bolus; giving dantrolene for LAST (or lipid for MH); ignoring MAC additivity; applying adult fasting rules to children; continuing airway attempts without declaring failure and switching algorithm.