What induction agent should be used in the emergency department to avoid hypotension and cardiac arrest in critically ill or injured patients, particularly those with cardiovascular disease or who are hemodynamically unstable?

Induction Agent Selection to Minimize Hypotension and Cardiac Arrest in the Emergency Department

Both etomidate and ketamine are acceptable first-line induction agents for emergency department RSI, with the 2023 Society of Critical Care Medicine guidelines suggesting no difference between them regarding mortality or hypotension risk, though individual patient hemodynamic status should guide selection. 1

Primary Recommendation Framework

The Society of Critical Care Medicine recommends administering a sedative-hypnotic induction agent when a neuromuscular blocking agent is used for intubation, even in hemodynamically unstable patients. 1 This is a best practice statement to prevent awareness during paralysis, which occurs in approximately 2.6% of emergency intubations. 2

Evidence-Based Agent Selection

• The 2023 Society of Critical Care Medicine guidelines suggest there is no difference between etomidate and other induction agents (including ketamine) with respect to mortality or the incidence of hypotension or vasopressor use in the peri-intubation period (conditional recommendation, moderate quality of evidence). 1

• Both ketamine and etomidate are supported as first-line induction agents by the Society of Critical Care Medicine. 2, 3

Etomidate: Hemodynamic Profile and Considerations

Advantages

• Etomidate has the most favorable hemodynamic profile among induction agents, with lower rates of peri-intubation hypotension (12.4%) compared to ketamine (18.3%) in National Emergency Airway Registry data. 4

• Etomidate is approximately 25 times more potent than thiopental with a therapeutic index six times greater, and does not cause histamine release. 5

Critical Limitation

• Despite etomidate-induced adrenal insufficiency through 11β-hydroxylase inhibition lasting 12-48 hours, the Society of Critical Care Medicine found no evidence this causes negative clinical outcomes. 3

• The Society of Critical Care Medicine suggests against administering corticosteroids following RSI with etomidate for the purpose of counteracting etomidate-induced adrenal suppression (conditional recommendation, low quality of evidence). 1

Ketamine: Hemodynamic Profile and Considerations

Advantages

• Ketamine maintains cardiovascular stability through sympathomimetic properties via endogenous catecholamine release, which is particularly beneficial in hypovolemic or shocked patients. 2, 3

• Ketamine causes bronchodilation, beneficial in patients with chest injuries, aspiration risk, or reactive airway disease. 3

• Ketamine is safe in head-injured patients when used with controlled mechanical ventilation, as historical concerns about increasing intracranial pressure have been refuted. 2, 3

Critical Pitfall

• In critically ill patients with depleted catecholamine stores (prolonged septic shock, severe cardiogenic shock, or adrenal exhaustion), ketamine may paradoxically cause hypotension and cardiac arrest despite its sympathomimetic properties. 2, 6

• Vasopressors should be immediately available during RSI with ketamine in these high-risk populations. 2, 6

Practical Dosing Algorithm

Ketamine Dosing

• Administer ketamine at 1-2 mg/kg IV for RSI, using the lower end of the dosing range (1 mg/kg) in patients with cardiovascular compromise to minimize hemodynamic effects while maintaining adequate sedation. 2, 3, 6

• Always administer ketamine BEFORE the neuromuscular blocking agent to prevent awareness during paralysis. 2, 6

Etomidate Dosing

• Standard etomidate dosing is 0.2-0.3 mg/kg, with 0.15 mg/kg used in patients with hemodynamic compromise. 1

Propofol: Avoid in Hemodynamically Unstable Patients

• Propofol has the most profound effect on blood pressure among induction agents and should be avoided in critically ill, hemodynamically unstable patients. 1

• The FDA label explicitly warns that slower rates of administration should be utilized in hemodynamically unstable patients, and fluid deficits should be corrected prior to administration. 7

• Propofol causes pronounced decreases in systolic, diastolic, and mean arterial pressures and cardiac output, particularly when combined with opioids or sedatives. 7

• In hemodynamically unstable patients where additional fluid therapy is contraindicated, elevation of lower extremities or use of pressor agents may be necessary to offset propofol-associated hypotension. 7

Clinical Decision Algorithm

For Hemodynamically Stable Patients

• Either etomidate or ketamine is appropriate, with no mortality difference between agents. 1, 3

For Hypovolemic/Hemorrhagic Shock Patients

• Ketamine is preferred due to sympathomimetic properties that maintain blood pressure through endogenous catecholamine release. 3

For Patients with Prolonged Septic Shock or Severe Cardiogenic Shock

• Etomidate may be preferred due to lower hypotension rates (12.4% vs 18.3%), as these patients likely have depleted catecholamine stores making ketamine's sympathomimetic effects unreliable. 4

For Trauma Patients

• Ketamine is preferred in hemodynamically unstable trauma patients due to sympathomimetic properties and bronchodilation benefits. 3

For Patients with Increased Intracranial Pressure

• Both ketamine and etomidate are acceptable when used with controlled mechanical ventilation. 2, 3

Essential Safety Measures

• Have vasopressors immediately available during RSI with any induction agent, as post-intubation hypotension is common and associated with increased mortality, prolonged ICU stays, and organ dysfunction. 1, 2, 3, 6

• Fluid deficits should be corrected prior to induction when possible. 7

• Midazolam should be avoided as it has a longer onset of action and is a potent venodilator at RSI doses. 1