Why is ketamine beneficial as an induction agent in trauma patients requiring Rapid Sequence Intubation (RSI)?

Why Ketamine is Beneficial as an Induction Agent in Trauma Patients Requiring RSI

Ketamine maintains hemodynamic stability through sympathomimetic properties while providing bronchodilation, making it particularly advantageous in hemodynamically compromised trauma patients who cannot tolerate the cardiovascular depression caused by alternative agents like propofol or thiopental. 1

Hemodynamic Advantages in Trauma

• Ketamine preserves blood pressure through endogenous catecholamine release, which is critical in trauma patients who may be hypovolemic or in shock 2
• Unlike propofol (which causes myocardial depression and vasodilation) or thiopental (which mandates cautious use with fluid infusion and vasoactive drugs), ketamine's sympathomimetic activity helps maintain cardiovascular stability 2
• The Society of Critical Care Medicine recommends ketamine (1-2 mg/kg IV) as a first-line induction agent alongside etomidate, with particular utility in hemodynamically unstable patients 1

Respiratory Benefits

• Ketamine causes bronchodilation, which is beneficial in trauma patients who may have concomitant chest injuries, aspiration risk, or underlying reactive airway disease 2
• Thiopental, by contrast, can lead to severe bronchoconstriction in patients with preexisting asthma or in the presence of cholinergic stimulation 2

Practical Dosing and Administration

• Administer ketamine at 1-2 mg/kg IV for RSI, using the lower end (1 mg/kg) in patients with cardiovascular compromise to minimize hemodynamic effects while maintaining adequate sedation 1
• The FDA label specifies that ketamine should be administered slowly over 60 seconds when given intravenously, as rapid administration may result in respiratory depression and enhanced vasopressor response 3
• Always administer ketamine BEFORE the neuromuscular blocking agent (succinylcholine 1-1.5 mg/kg or rocuronium 1.0-1.2 mg/kg) to prevent awareness during paralysis 1

Evidence from Trauma Studies

• A standardized RSI protocol using ketamine 2 mg/kg with rocuronium in 173 trauma patients (mean ISS 24) demonstrated significantly less need for medication redosing compared to varied protocols (3 patients vs 15 patients, p<0.05) and reduced time to intubation from 4 to 3 minutes 4
• A systematic review of ketamine versus other induction agents in trauma RSI found no significant differences in mortality, length of hospital stay, or blood transfusions, but importantly demonstrated that ketamine was not inferior to alternatives 5
• Recent meta-analysis of 23,926 patients showed no difference in 30-day survival between ketamine and etomidate, though ketamine required more post-intubation vasopressor support while etomidate caused significantly more adrenal insufficiency 6

Critical Caveats and Pitfalls

• Despite sympathomimetic properties, ketamine can cause paradoxical hypotension in critically ill patients with depleted catecholamine stores (prolonged shock, severe cardiogenic shock, or adrenal exhaustion) 1, 7
• Have vasopressors immediately available during RSI, as post-intubation hypotension occurs with all induction agents and is associated with increased mortality 7
• Ketamine increases upper airway secretions, which can be attenuated with atropine or glycopyrrolate pretreatment—this is particularly important in trauma patients at risk for aspiration 2
• Some observational data shows higher rates of post-intubation hypotension with ketamine (18.3%) compared to etomidate (12.4%) in emergency department RSI, though overall meta-analysis shows no significant difference (OR 1.10,95% CI 0.78-1.56) 7, 8

Comparison to Alternative Agents

• Etomidate has minimal cardiovascular effects but causes transient adrenal suppression (OR 2.43 for adrenal insufficiency) and is explicitly contraindicated in pediatric septic shock 1, 6
• Propofol causes myocardial depression and vasodilation even in euvolemic patients and should be employed with extreme caution in trauma casualties 2
• Thiopental can cause severe bronchoconstriction and requires cautious use with fluid infusion and vasoactive drugs 2

Specific Trauma Scenarios

• In head-injured patients, ketamine is safe and appropriate for RSI, particularly when used with controlled mechanical ventilation—historical concerns about increased intracranial pressure have been refuted by evidence from 2009-2013 7
• In hemodynamically unstable trauma, use the lower ketamine dose (1 mg/kg) to minimize risk of paradoxical hypotension while maintaining adequate sedation 1
• In burn patients and those requiring multiple procedures, ketamine has been extensively studied with over 12,000 operative and diagnostic procedures demonstrating safety and efficacy 3