What is the preferred induction agent for Rapid Sequence Intubation (RSI) in a patient with Status Asthmaticus (SCAPE)?

Preferred Induction Agent for RSI in SCAPE Patients

Ketamine is the preferred induction agent for rapid sequence intubation (RSI) in patients with Status Asthmaticus (SCAPE) due to its bronchodilatory properties and favorable hemodynamic profile. 1, 2

Rationale for Ketamine Selection

• Ketamine preserves respiratory drive and has sympathomimetic properties that help maintain hemodynamic stability, making it particularly valuable in SCAPE patients who may be hemodynamically compromised 1, 3
• Ketamine's bronchodilatory effects are beneficial in patients with bronchospasm, which is a key feature of status asthmaticus 2
• The Society of Critical Care Medicine guidelines recommend ketamine as an appropriate induction agent for RSI due to its quick onset, short duration of action, and ability to maintain hemodynamic stability 1

Dosing and Administration

• Recommended ketamine dosing for RSI: 1-2 mg/kg IV bolus 3, 4
• A sedative-hypnotic agent (ketamine) should be administered before the neuromuscular blocking agent to prevent awareness during paralysis 1
• Consider adding midazolam (reduced dose of 0.5-1 mg) to minimize recovery agitation, which is common with ketamine (number needed to treat: 6) 4

Alternative Induction Agents

• Etomidate (0.2-0.4 mg/kg) can be considered as an alternative when ketamine is contraindicated, as it also provides relatively stable hemodynamics 5
• Propofol should generally be avoided in SCAPE patients due to its potential for causing bronchospasm and significant hypotension 5, 6

Neuromuscular Blocking Agents for RSI

• Succinylcholine (1.5 mg/kg) is recommended as the first-line neuromuscular blocking agent for RSI in patients with vital signs of distress 5
• Rocuronium (0.9-1.2 mg/kg) should be used when succinylcholine is contraindicated 5
• Sugammadex should be readily available when rocuronium is used 5

Hemodynamic Considerations

• In a helicopter emergency medical services study, ketamine showed a 17.2% increase in systolic blood pressure compared to a 0.49% decrease with etomidate, making ketamine particularly valuable in potentially hypotensive SCAPE patients 7
• Ketamine had fewer episodes of post-administration hypotension compared to etomidate (p = 0.028) 7
• Peri-intubation hypotension is associated with increased mortality and prolonged ICU stays, making ketamine's hemodynamic stability particularly important 3

Post-Intubation Management

• Continue sedation immediately after intubation to prevent awareness during paralysis 3
• For ongoing sedation, ketamine can be continued at 0.5-1 mg/kg/hr infusion to maintain bronchodilation and hemodynamic stability 3
• Consider a recruitment maneuver and application of at least 5 cmH2O PEEP after intubation to improve oxygenation 5

Potential Pitfalls and Caveats

• Despite ketamine's generally favorable profile, some studies have shown conflicting results regarding hypotension risk. One study found higher rates of hypotension with ketamine compared to etomidate in ED patients undergoing RSI (18.3% vs 12.4%) 5
• Recovery agitation is common with ketamine but can be minimized with premedication with midazolam 4
• Limited high-quality evidence directly compares induction agents specifically in SCAPE patients, but ketamine's pharmacologic properties make it theoretically advantageous 8

While the evidence comparing induction agents specifically in SCAPE patients is limited, ketamine's bronchodilatory effects, sympathomimetic properties, and ability to maintain hemodynamic stability make it the preferred choice for this patient population.