Is ketamine contraindicated for induction in patients with hypertension?

Ketamine for Induction in Hypertensive Patients

Ketamine is contraindicated in patients for whom a significant elevation of blood pressure would constitute a serious hazard, including those with hypertension, as clearly stated in the FDA drug label. 1

Mechanism and Hemodynamic Effects

Ketamine is known to cause sympathomimetic effects that can significantly impact blood pressure:

• Ketamine typically causes transient increases in blood pressure and heart rate due to its sympathomimetic activity 1
• These hemodynamic effects are particularly concerning in patients with pre-existing hypertension
• The FDA label explicitly lists this contraindication, stating that ketamine is contraindicated "in patients for whom a significant elevation of blood pressure would constitute a serious hazard" 1

Evidence from Clinical Guidelines

Current guidelines support avoiding ketamine in hypertensive patients:

• The 2018 ACC/AHA guidelines for management of high blood pressure recommend careful selection of anesthetic agents in hypertensive patients, with consideration of hemodynamic effects 2
• For patients with acute coronary syndromes and hypertension, preferred agents include esmolol, labetalol, nicardipine, and nitroglycerin - not ketamine 2
• For induction in hemodynamically compromised patients, guidelines suggest that "hemodynamic stability would best be achieved during induction of anesthesia with drugs such as etomidate that have minimal effects on cardiovascular regulation" 2

Alternative Induction Agents

For hypertensive patients requiring induction, safer alternatives include:

• Etomidate: Provides hemodynamic stability with minimal effects on cardiovascular regulation 2, 3
• Propofol: Can be used with careful titration, though it may cause myocardial depression and vasodilation 2
• Midazolam: Can be considered, though it has venodilator effects at RSI doses 3

Special Considerations

1. Risk stratification: Patients with a high shock index (≥0.9) may have different responses to ketamine than those with low shock index (<0.9) 4

   • High shock index patients showed blunted hypertensive responses but more frequent hypotension (26%)
   • Low shock index patients had sustained increases in pulse rate and SBP, with 40% becoming hypertensive

2. Neurological concerns: While ketamine was traditionally contraindicated in patients with intracranial hypertension, more recent evidence suggests this may not be a concern in ventilated patients 5, 6

   • However, this does not override the contraindication for hypertensive patients

Management Algorithm for Induction in Hypertensive Patients

1. Avoid ketamine as the primary induction agent in patients with hypertension
2. Consider etomidate (0.2-0.3 mg/kg IV) as the first-line agent for induction in hypertensive patients 3
3. If etomidate is unavailable, consider carefully titrated propofol with vasopressors immediately available
4. Pre-induction preparation:
   • Have vasopressors immediately available
   • Ensure continuous hemodynamic monitoring
   • Consider pre-treatment with fentanyl (1-3 mcg/kg) to blunt sympathetic response 3, 7

Conclusion

Based on the FDA drug label and clinical guidelines, ketamine should be avoided for induction in hypertensive patients due to its sympathomimetic effects and the risk of dangerous blood pressure elevation. Etomidate represents a safer alternative for these patients.