What is the best intraoperative medication to treat hypotension in an older adult patient with a history of cardiovascular disease and hypertension, possibly undergoing surgery for aortic stenosis?

Intraoperative Hypotension Management in Older Adults with Cardiovascular Disease and Aortic Stenosis

For intraoperative hypotension in older adults with cardiovascular disease and aortic stenosis, norepinephrine is the preferred vasopressor, administered as a continuous infusion starting at 0.05-0.1 μg/kg/min, titrated to maintain MAP ≥60-65 mmHg or SBP ≥90 mmHg. 1

Blood Pressure Targets

• Maintain MAP ≥60-65 mmHg or SBP ≥90 mmHg intraoperatively to reduce risk of myocardial injury, acute kidney injury, and mortality 1
• Hypotension below these thresholds for >15 minutes is associated with significant postoperative complications 1
• In older adults with chronic hypertension, consider targeting higher MAP values (closer to 65-70 mmHg) rather than the minimum threshold 1

Vasopressor Selection: Norepinephrine vs Phenylephrine

Norepinephrine is superior to phenylephrine for several critical reasons in this patient population:

Hemodynamic Advantages of Norepinephrine

• Preserves cardiac output better than phenylephrine, with less reduction in stroke volume (-14% vs -18%) 2
• Reduces arterial stiffness less than phenylephrine, maintaining better arterial compliance (29% decrease vs 35% decrease) 2
• Lower augmentation index increase compared to phenylephrine (+6% vs +10%), indicating less afterload stress 2
• In severe aortic stenosis patients specifically, prophylactic norepinephrine infusion at 0.1 μg/kg/min prevents anesthesia-induced hypotension (lowest MBP 63 mmHg vs 47 mmHg in controls) 3

Critical Importance in Aortic Stenosis

Patients with severe aortic stenosis are particularly vulnerable to hypotension during anesthesia induction because:

• They depend on adequate preload and heart rate to maintain cardiac output 4
• Sudden drops in systemic vascular resistance can cause cardiovascular collapse 4
• Norepinephrine's combined alpha and beta effects maintain both vascular tone and cardiac contractility, which is essential in fixed cardiac output states 3

Renal Safety Profile

• Norepinephrine does not impair renal function in cardiac surgery patients, with no difference in postoperative creatinine changes compared to controls 5
• This addresses historical concerns about vasopressor-induced renal vasoconstriction 5

Practical Administration Protocol

Dosing Strategy

• Start norepinephrine infusion at 0.05-0.1 μg/kg/min at the time of anesthesia induction 3, 6
• Titrate to achieve target MAP, with maximum rates up to 2 μg/kg/min if needed 6
• Dilute in dextrose solution and infuse into a large vein to minimize extravasation risk 6
• Wean gradually postoperatively rather than abrupt discontinuation 6

Alternative Agents for Specific Situations

If norepinephrine is unavailable or contraindicated, the guideline-recommended alternatives for perioperative hypertension management include 1:

• Clevidipine, esmolol, nicardipine, or nitroglycerin for intraoperative blood pressure control 1
• Phenylephrine can be used as second-line, but expect greater reductions in cardiac output and arterial compliance 2
• Avoid pure beta-blockers in acute decompensation as they can worsen cardiac output in aortic stenosis 4

Critical Pitfalls to Avoid

• Never allow prolonged hypotension (MAP <65 mmHg for >15 minutes) while attempting fluid resuscitation alone 1
• Do not use vasopressors at inadequate doses out of fear of renal injury—the evidence shows norepinephrine is renal-safe 5
• Avoid phenylephrine as first-line in aortic stenosis due to its greater negative impact on stroke volume and arterial compliance 2
• Monitor for extravasation as tissue infiltration can cause local necrosis 6
• Ensure adequate preload before vasopressor initiation in aortic stenosis patients, as they are preload-dependent 4

Postoperative Considerations

• Resume oral antihypertensive medications as soon as clinically feasible to prevent rebound hypertension 1, 7
• Delaying resumption of chronic antihypertensives is associated with increased 30-day mortality 1, 7
• Continue calcium channel blockers perioperatively if the patient was on them chronically, as abrupt discontinuation increases risk 7, 8