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Delayed sequence intubation (DSI)
Delayed sequence intubation (DSI) is a novel technique for managing the airway in agitated patients who are not tolerating pre-oxygenation prior to endotracheal intubation. It represents a paradigm shift from rapid sequence intubation, which has been the traditional approach for emergency airways.
Indications:
DSI is specifically indicated for patients exhibiting agitated delirium or combative behavior that precludes adequate pre-oxygenation and optimal patient positioning prior to attempted intubation. These patients are at high risk for peri-intubation hypoxemia and physiologic decompensation with standard RSI.
Procedure:
The DSI protocol involves administering a dissociative dose of ketamine to sedate the agitated patient and facilitate pre-oxygenation, either via non-invasive ventilation or a bag-valve-mask device. Once adequate pre-oxygenation has been achieved, as evidenced by an oxygen saturation above 95%, standard neuromuscular blockade is administered to facilitate laryngoscopy and endotracheal intubation.
Pre-Oxygenation:
Place a non-rebreather mask and provide nasal cannula oxygen at 15 liters per minute. Position the patient upright or semi-upright to optimize gas exchange.
If the oxygen saturation is below 95%, proceed with C-Pap, Bi-Pap, or BMV with Peep valve 5 to 15 cm H2O for several minutes. Aim for SpO2 95% or more before pushing paralytic for intubation. If intubation is still needed, push paralytic, keep apneic oxygenation via nasal cannula, then intubate, confirm tube placement, and start post-intubation sedation. If at any point the oxygen saturation drops below 95%, despite non-invasive ventilation, proceed directly to intubation.
Advantages:
The primary advantage of DSI over RSI is the ability to optimize pre-oxygenation and patient positioning prior to attempting laryngoscopy. This minimizes the risk of peri-intubation hypoxia, a common complication of emergency airways. Additionally, by pre-treating agitation with ketamine sedation, DSI may improve first-pass intubation success rates.
Evidence:
In 2023, a randomized controlled trial was published, comparing DSI to RSI in trauma patients requiring emergent intubation. The trial found that, when compared to RSI, DSI was associated with significantly lower rates of peri-intubation hypoxia (8% vs 35%) and higher first-pass intubation success (83% vs 69%).
However, critics argue that routine use of DSI based on this single, low-quality trial represents premature adoption of an unproven technique. There are reasonable concerns about potential adverse events like laryngospasm or lost intravenous access during the "delayed" sequence.
Additionally, most intubations do not involve combative patients, the core indication for DSI. Applying DSI universally rather than selectively exposes many patients unnecessarily to the risks of ketamine sedation.
Implementation:
If considering DSI, it should be employed case-by-case, judiciously for appropriate indications only. Practitioners must ensure all equipment is prepared in advance, with a low threshold to proceed urgently with intubation if decompensation occurs during the "delay" after ketamine administration.