Airway/Original research
Delayed Sequence Intubation: A Prospective Observational Study

Presented as an abstract at the Society of Airway Management Scientific Assembly, September 2012, Toronto, Canada.
https://doi.org/10.1016/j.annemergmed.2014.09.025Get rights and content

Study objective

We investigate a new technique for the emergency airway management of patients with altered mental status preventing adequate preoxygenation.

Methods

This was a prospective, observational, multicenter study of patients whose medical condition led them to impede optimal preintubation preparation because of delirium. A convenience sample of emergency department and ICU patients was enrolled. Patients received a dissociative dose of ketamine, allowing preoxygenation with high-flow nonrebreather mask or noninvasive positive pressure ventilation (NIPPV). After preoxygenation, patients were paralyzed and intubated. The primary outcome of this study was the difference in oxygen saturations after maximal attempts at preoxygenation before delayed sequence intubation compared with saturations just before intubation. Predetermined secondary outcomes and complications were also assessed.

Results

A total of 62 patients were enrolled: 19 patients required delayed sequence intubation to allow nonrebreather mask, 39 patients required it to allow NIPPV, and 4 patients required it for nasogastric tube placement. Saturations increased from a mean of 89.9% before delayed sequence intubation to 98.8% afterward, with an increase of 8.9% (95% confidence interval 6.4% to 10.9%). Thirty-two patients were in a predetermined group with high potential for critical desaturation (pre–delayed sequence intubation saturations ≤93%). All of these patients increased their saturations post–delayed sequence intubation; 29 (91%) of these patients increased their post–delayed sequence intubation saturations to greater than 93%. No complications were observed in the patients receiving delayed sequence intubation.

Conclusion

Delayed sequence intubation could offer an alternative to rapid sequence intubation in patients requiring emergency airway management who will not tolerate preoxygenation or peri-intubation procedures. It is essentially procedural sedation, with the procedure being preoxygenation. Delayed sequence intubation seems safe and effective for use in emergency airway management.

Introduction

Preoxygenation and denitrogenation allow a safe buffer of oxygen to avoid hypoxemia during the apneic period of rapid sequence intubation.1 However, some patients struggle against traditional means of preoxygenation because of altered mental status. In these patients, we would be forced to proceed with rapid sequence intubation without the safety buffer of a large oxygen reservoir. Many of them will become hypoxemic during the apneic period and then require bag-valve-mask ventilation, with its attendant increased risks of gastric insufflation and aspiration.

Editor's Capsule Summary

What is already known on this topic

Adequate preoxygenation is difficult or even impossible in some patients with agitated delirium.

What question this study addressed

This small, observational study addresses whether a brief period of sedation with ketamine would improve ventilation and preoxygenation before intubation.

What this study adds to our knowledge

Postsedation oxygen saturations were successfully increased in the majority of patients.

How this is relevant to clinical practice

Delayed sequence intubation provides a feasible option for preoxygenation in the patient with altered mental status resistant to standard preoxygenation. Clinical outcomes were not assessed, and a randomized trial is warranted.

In contrast to rapid sequence intubation, the technique of delayed sequence intubation temporally separates administration of the induction agent from the administration of the muscle relaxant to allow adequate preintubation preparation.2 The induction agent chosen is one that allows the continuation of spontaneous breathing and the retention of airway reflexes. The prototypical agent for this purpose is ketamine, a dissociative NMDA receptor antagonist. In the space of this separation, the patient can be preoxygenated and denitrogenated, and any necessary peri-intubation procedures can be performed. Only after completion of these crucial actions would the patient be paralyzed and intubated.

Patients who are intubated without adequate preoxygenation will have less apneic tolerance and are at risk for precipitous desaturation during intubation.1 If the patient’s preintubation oxygen saturation is less than or equal to 93%, he or she will likely continue to desaturate during the apneic period.3 Patients with inadequate preoxygenation and denitrogenation will have much shorter times until desaturation during intubation attempts.1 A technique to allow adequate preparation of delirious or combative patients for intubation could decrease the risk of hypoxemia and reduce peri-intubation morbidity and mortality.4

Our aim was to investigate the technique of delayed sequence intubation in a cohort of emergency department (ED) and critical care patients requiring emergency airway management in regard to improvement in preoxygenation and safety.

Section snippets

Study Design

This was a prospective, observational study of patients whose medical condition or mental status led them to impede optimal preoxygenation, denitrogenation, or preintubation procedures. A convenience sample of patients was enrolled during the study period. Clinicians made attempts to preoxygenate and denitrogenate the study participants. If these patients did not allow the necessary preintubation preparations because of delirium, ketamine was administered until they became dissociated. At this

Results

Sixty-four patients with delayed sequence intubation were included from May 2011 to December 2013 (Figure 2). Two patients were excluded because the pulse oximeter would not register a post–delayed sequence intubation oxygen saturation. Both of these patients had arterial blood gases sent from their arterial lines at this point; the SaO2 values of these blood gases were both 100% and neither of these patients had any complications.

The Table summarizes the characteristics of the remaining 62

Limitations

This was not a randomized trial and therefore it is unknown what the patient outcomes would have been in these cases if delayed sequence intubation had not been used. We collected patients as a convenience sample when the clinician deemed that delayed sequence intubation would have been beneficial; hence, there may be inherent selection bias. It is possible that a delayed sequence intubation was performed at one of these centers but the patient was not enrolled in the study. This is unlikely

Discussion

In this prospective trial, we found that delayed sequence intubation allowed the provision of preoxygenation and denitrogenation to a patient population who would otherwise have been resistant to these important procedures. Traditionally, these patients would have proceeded directly to rapid sequence intubation, exposing them to the risks of peri-intubation bag-valve-mask ventilation such as gastric insufflation and aspiration. In patients with physiologic shunting, inadequate recruitment and

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Please see page 350 for the Editor’s Capsule Summary of this article.

Supervising editor: Gregory W. Hendey, MD

Author contributions: SDW was responsible for the overall study and statistical review, was the principal investigator, collated comments from other authors, prepared the final article, had full access to all the data in the study, and takes responsibility for the integrity of the data and the accuracy of the data analysis. ST, JS, and NS were responsible for data collection. SDW and SSR were responsible for analysis and interpretation of the data and for study design. All authors critically reviewed the article. SDW takes responsibility for the paper as a whole.

Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.

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