Delayed Sequence Intubation: A Prospective Observational Study

Weingart, Annals of Emergency Medicine;2014; published online. doi:10.1016/j.annemergmed.2014.09.025

Clinical Question

  • In patients who require emergency intubation and are not tolerating pre-oxygenation, does the use of ‘delayed sequence intubation’ (DSI) improve pre-intubation oxygen saturations (SpO2)?


  • Prospective observational case series
    • non-randomised
    • non-blinded
    • convenience sample


  • 3 hospital in USA/Denmark
  • Level 1 trauma centre or quarternary referral centre
  • Study period: May 2011 to December 2013


  • Inclusion:
    • Adult patient spontaneously breathing who were required to have emergency intubation
    • Not predicted to have difficult airway
    • Did not tolerate pre-oxygenation despite maximal conventional attempts
  • 62 patients included in analysis out of 64 enrolled


  • Ketamine
    • Initial dose 1mg/kg, followed by 0.5mg/kg aliquots until dissociated
    • Then placed ≥30 degrees head up and pre-oxygenated with non-rebreather mask and nasal cannula
    • If SpO2 <95% then changed to CPAP 5-15cm H2O
      • 39 patients received pre-oxygenation with CPAP
      • 23 patients did not require CPAP
    • After 3 minutes paralysed with suxamthonium/rocuronium and intubated after further 45-60 seconds


  • No control group


  • Primary outcome
    • Difference in SpO2 after pre-oxygenation with:
      • a) standard attempts
      • b) ketamine (just prior to administration of muscle relaxation)
    • significant increase post ketamine
      • 88.9% vs 98.8% (increase of 8.9%, 95% C.I. 6.4-10.9)
  • Secondary outcomes:
    • Subgroup analysis
      • SpO2 after pre-oxygenation with ketamine in patients with initial SpO2 ≤93% after pre-oxygenation with standard attempts
        • all increased SpO2 to >93%
    • Complications
      • No patients had pre-muscle relaxant apnoea, peri-intubation emesis, cardiac arrest or death
      • 2 patients SpO2 decreased after attempting pre-oxygenation with ketamine
        • decrease from 99% to 98% and 95% to 93% respectively
        • both of these patients received pre-oxygenation by nonrebreather masks without nasal cannula oxygen during their dissociation
  • Post-hoc analysis
    • 2 patients with asthma improved sufficiently with pre-oxygenation with ketamine and CPAP that decision made not to intubate them

Authors’ Conclusions

  • DSI safely allowed the provision of pre-oxygenation to patients who did not tolerate pre-oxygenation with traditional methods


  • Multi-centre
  • Prospective
  • Standard protocol for use of DSI
  • Sensitivity analysis performed for possible non-parametric distribution


  • No control group
  • Non blinded
  • Convenience sample – therefore possibility of selection bias although authors comment that independent research fellow did not find evidence supporting this.
  • DSI performed by clinicians with extensive experience of ketamine sedation and therefore results may not represent expected outcomes in less experienced hands

The Bottom Line

  • In a prospective observational study of patients requiring emergency intubation who did not tolerate pre-oxygenation with traditional methods, the practice of DSI significantly improved oxygen saturations prior to intubation. A RCT is warranted, comparing the use of DSI with the use of other techniques for achieving pre-oxygenation, when traditional methods have failed. In the mean time, on the basis of this level 4 evidence I will use the practice of DSI in selected cases.

External Links


Summary author: @davidslessor
Summary date: 3rd November 2014
Peer-review editor: @DuncanChambler

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