Delayed Sequence Intubation and Its Role in Prehospital Emergency Medicine: A Scoping Review

OBJECTIVE: Preoxygenation is a key component of prehospital emergency anesthesia (PHEA), reducing hypoxemia and increasing safe apnea time. Delayed sequence intubation (DSI) involves the use of sedation without blunting respiratory drive to facilitate optimization, primarily oxygenation, before paralytic administration and subsequent intubation in patients with agitation who are unable to tolerate preoxygenation. This scoping review explored the evidence supporting DSI in emergency and prehospital practice. METHODS: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-guided scoping review was conducted. MEDLINE and Embase were searched from inception to May 5, 2025, for studies reporting DSI. Primary studies, case series, case reports, and guidelines involving adult or pediatric patients were included; reviews, editorials, and letters were excluded. Titles, abstracts, and full texts were independently screened by 2 reviewers, with disagreements resolved by a third. RESULTS: Fourteen studies met the inclusion criteria. Across these studies, 310 DSI cases were reported, including 140 performed prehospital by physician- and paramedic-led teams. Emergency department evidence suggests that DSI may reduce hypoxemia in agitated patients compared with rapid sequence intubation (RSI), with 1 randomized controlled trial reporting hypoxemia rates of 8% versus 35% (P = .001). Evidence specific to prehospital DSI was limited to retrospective studies, with no randomized controlled trials identified. CONCLUSION: Limited evidence suggests that DSI can be performed by teams already delivering PHEA using an RSI technique and may reduce hypoxemia in those patients unable to tolerate preoxygenation. Further prospective research directly comparing RSI and DSI techniques in the prehospital setting is required to inform future practice.