How would you anesthetize this patient for cardiac or noncardiac surgery?
Premedication in patients with AS has to be carefully administered. Oversedation may lead to hypotension and decreased CPP, while undersedation may result in an anxious, tachycardic patient who is prone to myocardial ischemia. Patients with AS are critically sensitive to preload and an appropriate intravascular volume status has to be assured prior to anesthesia induction. Systemic vascular resistance (SVR) must be maintained at all times. Thus, neuraxial anesthesia with the risk of sympatholysis is rela-tively contraindicated in patients with AS. Dysrhythmias are poorly tolerated, making maintenance of a sinus rhythm imperative. A defibrillator should be readily avail-able in the operating room.
Perioperative monitoring should be according to the rec-ommendations of the American Society of Anesthesiol-ogists. Patients with AS are at increased risk for ischemia and dysrhythmias and monitoring should include leads II and V5. The sensitivity of this lead combination for detecting myocardial ischemia is approximately 80%. A pulmonary artery catheter is routinely used to estimate left-sided filling pressures in some centers, but this remains controversial.
The main goals for inducing anesthesia in patients with AS are to avoid major alterations in preload, afterload, heart rate, and contractility. Thus, etomidate opioids, and mida-zolam are reasonably good choices, but should be titrated to effect. Vecuronium and cisatracurium are neuromuscular blockers with favorable hemodynamic profiles. Drugs such as ketamine and pancuronium may increase heart rate and should be avoided. Thiopental may cause decreased preload and should probably be avoided. Similarly, propofol is asso-ciated with hypotension and should probably be avoided.
Anesthesia can be maintained with many different tech-niques so long as the preload, afterload, heart rate, and contractility are monitored to avoid adverse hemodynamic responses. Opioids, benzodiazepines, potent volatile anes-thetics, and nitrous oxide should all be titrated, paying careful attention to maintaining perfusion pressure. Tachycardia, bradycardia, and loss of sinus rhythm are all problematic. Stroke volume across the stenotic aortic valve is relatively fixed and is lower than normal; thus, an α-agonist, such as phenylephrine, is the agent of choice for treating hypotension.