Contraindications for Ketamine as an RSI Induction Agent
Ketamine is contraindicated in patients where a significant elevation of blood pressure would constitute a serious hazard, and in those with known hypersensitivity to ketamine or its excipients. 1
Absolute Contraindications
Cardiovascular Conditions Where Blood Pressure Elevation is Dangerous
- Patients with uncontrolled severe hypertension where further blood pressure elevation could precipitate end-organ damage 1
- Acute aortic dissection where sympathomimetic effects could extend the dissection 1
- Acute coronary syndrome with severe hypertension where increased myocardial oxygen demand could worsen ischemia 1
- Intracranial hemorrhage with uncontrolled hypertension where further pressure elevation could extend bleeding 1
- Known hypersensitivity to ketamine or any excipient 1
Relative Contraindications and High-Risk Populations
Critically Ill Patients with Depleted Catecholamine Stores
In critically ill patients with depleted catecholamine stores, ketamine may paradoxically cause hypotension and cardiac arrest despite its sympathomimetic properties. 2, 3 This occurs because ketamine's hemodynamic stability depends on endogenous catecholamine release, which may be exhausted in:
- Prolonged septic shock patients 2
- Patients with severe cardiogenic shock 2
- Those with prolonged critical illness and adrenal exhaustion 2
Evidence on Hemodynamic Complications
The evidence regarding ketamine's hemodynamic profile reveals important nuances:
Recent meta-analysis shows no difference in 30-day survival between ketamine and etomidate, though ketamine was associated with higher post-intubation vasopressor requirements (OR 0.71,95% CI: 0.53-0.96) 4
Multiple observational studies demonstrate higher rates of post-intubation hypotension with ketamine compared to etomidate in certain populations, with rates of 18.3% vs 12.4% in emergency department RSI 2, 5
Full-dose ketamine (>1.25 mg/kg) was associated with the highest rate of post-intubation hypotension (36.5%) in one recent study, though these patients had worse baseline hemodynamics 6
Air medical transport data showed ketamine associated with higher incidence of hypotension and arrest, likely reflecting selection bias toward more unstable patients 7
Clinical Decision Algorithm
When to AVOID Ketamine:
- Absolute contraindication present (uncontrolled severe hypertension, aortic dissection, known allergy) 1
- Prolonged shock state with suspected catecholamine depletion (consider etomidate instead) 2
- Hemodynamically stable STEMI patients (midazolam showed worse outcomes, but ketamine data limited in this specific population) 8
When Ketamine is APPROPRIATE:
- Hemodynamically stable patients without contraindications 2
- Head-injured patients requiring controlled ventilation (historical concerns about ICP elevation are outdated) 3
- Status epilepticus patients (safe with controlled ventilation) 9
- Patients requiring hemodynamic support but with intact sympathetic response 2
Dosing Considerations to Minimize Risk
Use reduced-dose ketamine (1 mg/kg) in patients with cardiovascular compromise rather than standard 2 mg/kg dosing 3, 9. However, note that even reduced-dose ketamine may cause hypotension in severely depleted patients 2.
Critical Safety Points
Always have vasopressors immediately available during RSI with any induction agent, as post-intubation hypotension is common (occurs in ~27.9% of cases) and associated with increased mortality, prolonged ICU stays, and organ dysfunction 2, 9, 8
Administer ketamine BEFORE the neuromuscular blocking agent to prevent awareness during paralysis, which occurs in approximately 2.6% of emergency intubations 5, 3, 9
The 2023 Society of Critical Care Medicine guidelines suggest no difference between etomidate and other induction agents (including ketamine) with respect to mortality or hypotension (conditional recommendation, moderate quality evidence), though individual patient factors should guide selection 2