What is the medication of choice for a delayed sequence intubation, particularly in patients with potential cardiovascular instability or impaired respiratory function?

Medication of Choice for Delayed Sequence Intubation

Ketamine at a dose of 1-1.5 mg/kg IV is the medication of choice for delayed sequence intubation (DSI). 1, 2

What is Delayed Sequence Intubation?

DSI is a technique specifically designed for agitated, delirious, or combative patients who cannot tolerate standard preoxygenation devices. 1 The procedure involves administering ketamine to achieve a dissociative state, allowing 3 minutes of effective preoxygenation, followed by administration of a neuromuscular blocking agent and then intubation. 1

Why Ketamine is the Optimal Choice

Ketamine's unique pharmacologic profile makes it ideal for DSI:

• Preserves respiratory drive - Unlike other sedatives, ketamine maintains spontaneous ventilation during the preoxygenation period, which is critical for patient safety. 3, 4

• Maintains hemodynamic stability - Ketamine's sympathomimetic properties help preserve blood pressure and heart rate, making it particularly valuable in hemodynamically unstable patients. 5, 2, 3

• Rapid onset and appropriate duration - Ketamine provides quick sedation with a duration that allows adequate time for preoxygenation without excessive delay. 3

• Dissociative properties - Creates a state where patients are sedated but maintain protective airway reflexes during the preoxygenation phase. 4

DSI Protocol Using Ketamine

Step-by-step approach:

1. Administer ketamine 1-1.5 mg/kg IV to achieve dissociative sedation. 1, 2

2. Preoxygenate for 3 minutes using high-flow nasal oxygen, non-invasive positive pressure ventilation, or facemask with CPAP while the patient breathes spontaneously. 1

3. Administer neuromuscular blocking agent - Either rocuronium (0.9-1.2 mg/kg) or succinylcholine (1-1.5 mg/kg) depending on contraindications. 5, 2

4. Proceed with intubation once paralysis is achieved. 1

Critical Safety Considerations

Never administer the neuromuscular blocking agent before the sedative-hypnotic agent (ketamine). This sequence is essential to prevent awareness during paralysis, which occurs in approximately 2.6% of emergency department intubations when sedation is inadequate. 2, 3

When DSI is Specifically Indicated

DSI should be chosen over standard RSI in these scenarios:

• Agitated or combative patients who actively resist preoxygenation attempts. 5, 1

• Delirious patients unable to cooperate with mask placement. 5, 1

• Severe hypoxemia with agitation - The combination of inability to preoxygenate plus critical hypoxemia makes DSI particularly valuable, as inadequate preoxygenation poses greater immediate risk than the theoretical increased aspiration risk from delayed paralysis. 1

Common Pitfall to Avoid

The most critical error is using DSI in cooperative patients with high aspiration risk. 1 In cooperative patients, standard RSI should be performed even if they have aspiration risk, as they can tolerate preoxygenation without medication-assisted sedation. 1 DSI is reserved specifically for patients whose agitation prevents adequate preoxygenation - the inability to preoxygenate is the primary indication, not the presence of hypoxemia alone. 1

Evidence Supporting Ketamine for DSI

Studies demonstrate that ketamine administration for medication-assisted preoxygenation increases oxygen saturation by a mean of 8.9% before neuromuscular blockade is administered. 1 The British Journal of Anaesthesia guidelines increasingly favor ketamine in most circumstances for critically ill patients due to hemodynamic considerations. 5 The Society of Critical Care Medicine specifically recommends medication-assisted preoxygenation (DSI) for patients unable to tolerate preoxygenation devices due to agitation, delirium, or combative behavior. 1