General Anesthesia and Perioperative Management
Core concepts
Candidates must command the arc of a general anesthetic: preassessment and risk stratification (ASA class, functional capacity, frailty), aspiration and VTE risk, fasting intervals, and the choice of induction, maintenance, and emergence strategy. Understand MAC as a comparative potency measure, the additive nature of volatile and nitrous oxide MAC, and factors that shift requirement (age, temperature, pregnancy, opioids, alcohol). Know the physiology of positive-pressure ventilation and its effects on preload and venous return. Perioperative management includes PONV prophylaxis (Apfel scoring), multimodal analgesia, normothermia, glucose control in diabetics, and evidence-based ERAS pathways.
Traps in questions
- Confusing MAC with a depth-of-anesthesia monitor; it is a potency benchmark, not a target reading.
- Forgetting that MAC-awake is roughly one-third of MAC and that nitrous oxide reduces other agents' MAC.
- Overlooking that succinylcholine and volatile agents are triggers for malignant hyperthermia, and that dantrolene is the specific antidote.
- Assuming fasting guidelines are the same for clear fluids and solids; clear fluids are permitted closer to induction in most guidelines.
- Misreading an ASA class question where the disease is well controlled versus poorly controlled.
Worked example / rule of thumb
A 70-year-old with well-controlled hypertension and no functional limitation is ASA II; if the hypertension were poorly controlled with end-organ damage, ASA III. For MAC math: if agent A has MAC 2% and you run 1% with 50% nitrous oxide (MAC ~0.5 of the mixture), the combined MAC fraction is 0.5 + 0.5 = 1.0. Rule of thumb: add MAC fractions, not percentages.
Exam framing
Expect vignettes asking which single change most reduces a named complication (e.g., PONV, surgical site infection, hypothermia). Answer with the intervention with the strongest evidence, not the most elaborate one.