Neuromuscular Blockade and Successful Endotracheal Intubation

By Samuel Nadler, MD, PhD

Critical Care, Pulmonary Medicine, The Polyclinic Madison Center, Seattle, WA

Dr. Nadler reports no relationships relevant to this field of study.

SYNOPSIS: In this single-center observational study, the use of neuromuscular blockade during intubation improved first attempt success.

SOURCE: Mosier JM, et al. Neuromuscular blockade improves first attempt success for intubation in the intensive care unit: A propensity matched analysis. Ann Am Thorac Soc 2015 Feb 26 [Epub ahead of print].

Previous studies have shown the utility of neuromuscular blocking agents (NMBA) for endotracheal intubation in the operating room and emergency department. However, airway management in the ICU often involves unplanned, emergent intubations under suboptimal conditions. This study asked whether NMBAs improved first attempt success (FAS) of intubations in the ICU. Additionally, these authors asked whether succinylcholine or rocuronium improved first attempt success and the effects of NMBA on intubations using video laryngoscopy.

This was a single-center, prospective, observational study of 664 consecutive intubations in a major academic referral center from Jan 1, 2012, to June 30, 2014. Using this cohort, NMBAs significantly improved FAS (80.9%, 401/496) as compared with intubations performed without NMBA (69.6%, 117/168; P = 0.003) with an odds ratio (OR) of 1.84 (95% CI, 1.24-2.74). In patients intubated with video laryngoscopy specifically, NMBA also led to a higher FAS (84.6%, 334/394 vs 69.1%, 103/149; P < 0.001). There were no significant differences in age, gender, individual difficult airway characteristics, or reasons for intubation between these two groups, but the patients intubated without NMBA had a higher median number of difficult airway characteristics, higher use of ketamine as an induction agent, and tended to be intubated by a physician with a higher level of training. There was no difference in complication rates between those intubated with and without NMBA, and there was no difference in outcomes in patients intubated with rocuronium vs succinylcholine.

As this was an observational study, the authors developed a propensity score to address potential clinical confounders in their analysis. This score was generated using variables that might influence clinicians’ use of NMBA such as the presence of difficult airway conditions, emesis, trauma, airway edema, obesity, etc. The score was then used to generate 5000 data sets of cases of failed first attempts matched with successful controls with similar propensity scores, and conditional logistic regression was used to analyze the outcomes. Using these data, NMBA led to a greater FAS with an odds ratio of 2.37 (95% CI, 1.36-4.88) in the logistic regression model and a propensity score-adjusted odds ratio of 2.22 (95% CI, 1.32-3.75).

COMMENTARY

The authors address a clinical question that has not previously been well studied, the utility of NMBA in endotracheal intubations in the ICU. However, this was an observational study and subject to bias. Although the patient demographics seem closely matched and the propensity score is used to reduce this bias, other variables than those in the propensity score could influence outcomes. For example, in the NMBA group, many more patients were given etomidate (83.3%) than in the control group (34.5%). The use of ketamine and propofol was far lower in the NMBA group (8.9% vs 39.3% and 5.0% vs 11.3%, respectively). Thus, these conclusions must be interpreted with caution.

Other variables not in the primary analysis may have equal or greater effects on FAS than the choice of using NMBA. In this study, video laryngoscopy improved FAS rates with an unadjusted OR of 1.87 to 2.58 compared with direct laryngoscopy, depending on the device. The level of training also had a significant influence with attending level providers having an OR = 8 of first attempt success compared with PGY-1s (95% CI: 0.97-65.82).

Overall, this study provides preliminary evidence that neuromuscular blockade agents improve first attempt success rates both with direct laryngoscopy and video laryngoscopy, although these findings should be replicated in a randomized, prospective study.