Induction in Critical Aortic Stenosis: Trusting the Agent or Trusting the Technique
A 79-year-old woman with critical aortic stenosis needs induction for urgent aortic valve replacement. The disagreement isn't about which drug looks best on paper — it's about whether her own chronic beta-blockade quietly disqualifies the agent that looks best on paper.
Dorothy K., a 79-year-old woman, still lived alone and drove herself to church every Sunday until three weeks ago, when she fainted getting up from a pew and was caught by the man in the next row before her head reached the floor. The workup that followed found critical aortic stenosis — a valve area of 0.6cm², a mean gradient of 64mmHg — on a heart that had otherwise been keeping her upright and independent for two decades since her hypertension diagnosis. Her cardiologist started a low-dose beta-blocker years ago for rate control alongside her lisinopril, and she has taken metoprolol 25mg twice daily without incident ever since, long before anyone suspected her valve was the real problem. Her heart rate on arrival is 58, which is not the reassuring number it looks like: it measures how completely that metoprolol is still working, and it means any drug whose hemodynamic reputation rests on provoking a sympathetic response will not find one available to provoke in her.
Her EF is preserved at 58%, which on its own would read as reassuring, except that a preserved EF in critical AS is not evidence her heart is coping — it is the fixed obstruction itself holding stroke volume artificially stable at the cost of a hypertrophied, poorly compliant ventricle with almost no reserve left to draw on. That fixed stroke volume is the whole problem with induction: she cannot answer a fall in systemic vascular resistance by ejecting more, so whatever drops her afterload drops her coronary perfusion pressure with nothing to offset it. The syncope that brought her in is the marker guidelines treat as decisive — symptomatic severe AS carries a natural history measured in months, not years, once syncope appears — and she is scheduled for urgent AVR before that clock runs further. The agent that best protects that physiology, etomidate, carries the objection everyone in the room already knows: den Brinker's cohort documented adrenocortical suppression lasting at least twenty-four hours after a single bolus. That was measured in children with meningococcal sepsis, whose cortisol response was load-bearing for survival in a way an uninfected 79-year-old's is not — a claim about whether the finding describes her, not about whether it is real. What the team is working through before she reaches the OR is not whether to operate, which is settled, but what she should be given at the moment her own compensation is handed over to a drug.
Before the first milligram
Etomidate. Her stroke volume is fixed across that valve — nothing she does with her own physiology can increase it to compensate for a drop in SVR the way a normal ventricle would. Etomidate is the one agent in the room that doesn't ask her vasculature to do anything at all.
I'm not dismissing the adrenal question, and I don't want to misstate it either. den Brinker's cohort found measurable adrenocortical suppression lasting at least twenty-four hours after one single bolus — so I can't wave this away as a repeated-dosing problem that a one-time induction dose escapes. It isn't. What I can argue is the population. That work was done in children with meningococcal sepsis, patients whose adrenal axis was already being overwhelmed by the illness itself and whose cortisol response was load-bearing for survival. Dorothy is seventy-nine, walking in for an elective-urgent valve operation with no infection and no reason to think her axis is already failing. The suppression is real; whether it matters in a patient who isn't relying on a stress cortisol response to stay alive is a different question, and that's the one that decides her case.
I'll grant the adrenal point — you're right that a single bolus isn't the den Brinker exposure. But I want the room to notice what nobody's said yet: ketamine isn't actually on the table for her, and it's worth saying why out loud rather than letting it drop silently. Ketamine's hemodynamic reputation is built on indirect sympathetic stimulation — it works by releasing catecholamines centrally, which masks a real direct negative inotropic effect at the myocardium.
She's been on metoprolol twice daily for years. A beta-blocked patient can't mount the sympathetic surge ketamine depends on to look stable — so what she'd actually experience is closer to the unmasked direct depressant effect than to the textbook drug. This isn't a reason to prefer etomidate over ketamine in general; it's a reason her chart specifically rules ketamine out.
Agreed on ruling out ketamine, for exactly that reason. But I'd push back gently on treating this as purely a drug-choice question. We already have a phenylephrine infusion running before she's asleep. A reduced dose of propofol, given slowly over ninety seconds instead of pushed, behaves differently than the drug's reputation suggests — the vasodilation is dose- and rate-dependent, and we're controlling both.
I'm not arguing against etomidate here — it's a reasonable, defensible choice and I won't fight for propofol over her objection to a longer discussion in the room. I'm naming it so the team doesn't walk away thinking etomidate was the only physiologically sound option, because the next AS patient may have an adrenal or infection concern that makes this conversation matter more.
Agreed: etomidate 0.2mg/kg for induction, phenylephrine infusion running beforehand, arterial line already in place before the first dose. Ketamine excluded explicitly, not silently, for the beta-blockade reasoning above.
Not agreed, and left as an open teaching point rather than smoothed over: whether technique-controlled propofol should be considered co-equal to etomidate as a default in similar patients going forward, or reserved for cases where etomidate carries a specific contraindication. The second cardiac anesthesiologist's position was accepted as reasonable for today's patient without resolving which approach the group would reach for first the next time.