In which patient population is Delayed Sequence Intubation (DSI) more beneficial than Rapid Sequence Intubation (RSI)?

Delayed Sequence Intubation (DSI) vs Rapid Sequence Intubation (RSI): Optimal Patient Populations

DSI is most beneficial in agitated, delirious, or combative patients who cannot tolerate standard preoxygenation methods (face mask, NIPPV, or HFNO) due to their mental status, as this approach significantly reduces peri-intubation hypoxia compared to RSI in this specific population. 1, 2

Primary Indication: Agitated/Uncooperative Patients

The Society of Critical Care Medicine specifically recommends medication-assisted preoxygenation (DSI) for patients who are unable to tolerate preoxygenation devices because of agitation, delirium, or combative behavior. 1, 2 This represents a conditional recommendation with very low quality evidence, but the clinical rationale is compelling. 1

Evidence Supporting DSI in This Population

• In critically injured trauma patients, DSI reduced peri-intubation hypoxia from 35% (RSI group) to 8% (DSI group), representing a 77% relative risk reduction. 3
• DSI improved first-attempt intubation success rates from 69% to 83% in agitated trauma patients. 3
• Ketamine administration for DSI increased mean oxygen saturation by 8.9% before neuromuscular blockade administration, achieving 98.9% saturation compared to 89.9% with standard RSI. 1, 2

Clinical Algorithm for Choosing DSI vs RSI

Step 1: Assess Patient Cooperation

• If patient is cooperative and can tolerate face mask/NIPPV/HFNO: Use standard RSI 2
• If patient is agitated, delirious, or combative and cannot tolerate preoxygenation: Use DSI 1, 2

Step 2: Evaluate Aspiration Risk

• High aspiration risk with cooperative patient: Standard RSI remains preferred 2
• High aspiration risk with uncooperative patient: DSI is still indicated, as inadequate preoxygenation poses greater immediate risk than the theoretical increased aspiration risk from delayed paralysis 1, 3

Step 3: Assess Oxygenation Status

• Severe hypoxemia (PaO2/FiO2 < 150) in cooperative patient: Use RSI with NIPPV for preoxygenation 1
• Severe hypoxemia in uncooperative patient: DSI becomes even more critical, as these patients are at highest risk for catastrophic desaturation 1, 3

DSI Protocol Specifics

The technique involves administering ketamine (typically 1-1.5 mg/kg IV) to achieve a dissociative state, followed by 3 minutes of preoxygenation, then administration of the neuromuscular blocking agent and intubation. 1, 3, 4

Key Safety Considerations

• Apnea risk: One study reported brief self-limiting apnea (<15 seconds) in 1 of 40 patients receiving DSI, which resolved spontaneously. 4
• Hemodynamic stability: DSI with ketamine maintains hemodynamic stability better than other induction agents in critically ill patients. 3, 4
• Awareness prevention: The sedative-hypnotic agent (ketamine) must always be administered before the neuromuscular blocking agent to prevent awareness during paralysis. 1, 5

Populations Where DSI Should NOT Replace Standard RSI

Standard RSI remains the preferred approach for: 2

• Cooperative patients who can tolerate preoxygenation
• Patients at high aspiration risk who are cooperative
• Most emergency intubations where adequate preoxygenation can be achieved

The British Journal of Anaesthesia guidelines emphasize that RSI should be performed early in patients with cervical spine injury using manual-in-line stabilization, as the risk of cervical movement is highest with face mask ventilation. 1 In this population, if the patient is cooperative, standard RSI is preferred over DSI.

Common Pitfalls and How to Avoid Them

• Using DSI routinely instead of selectively: DSI is not a replacement for standard RSI in all patients; it is specifically for those who cannot tolerate preoxygenation due to mental status. 1
• Inadequate ketamine dosing: Use full dissociative doses (1-1.5 mg/kg) rather than subdissociative doses to ensure adequate sedation for preoxygenation. 3, 4
• Rushing the preoxygenation period: Allow the full 3 minutes of preoxygenation after ketamine administration before giving the neuromuscular blocking agent. 3
• Forgetting post-intubation sedation: After intubation with DSI, ensure immediate transition to appropriate post-intubation analgosedation, as the ketamine effect will wear off. 2, 5