By Eric Walter, MD, MSc
Pulmonary and Critical Care Medicine, Northwest Permanente and Kaiser Sunnyside Medical Center, Portland, OR
Dr. Walter reports no financial relationships relevant to this field of study.
SYNOPSIS: In emergent intubations, a position in which the angle of the back was > 30 degrees above the horizontal (head-elevated) position was associated with fewer complications than intubations performed in the supine position, but the study has several limitations.
SOURCE: Khandelwal N, Khorsand S, Mitchell SH, et al. Head-elevated patient positioning decreases complications of emergent tracheal intubation in the ward and intensive care unit. Anesth Analg 2016:122:1101-1107.
Emergent endotracheal intubation is a life-saving procedure commonly performed in the ICU. It is also a risky procedure with potential life-threatening complications. Back-up, head-elevated (BUHE) describes a patient position that has been shown in the surgical patient to improve preoxygenation and glottis views during direct laryngoscopy. The BUHE position differs from the sniffing position by ensuring the angle of the back is above the horizontal plane.
Khandelwal et al retrospectively sought to determine if the BUHE position (defined as head-elevated position in this study), as compared to a supine position, was associated with decreased complications during emergent intubation on the wards or in the ICU. Head-elevated was defined as placing the angle of the back ≥ 30 degrees above the horizontal. Anything < 30 degrees was categorized as supine. The primary outcome was a composite of airway complications during or shortly after intubation. Complications included hypoxemia (SpO2 < 90% during or within 15 minutes of intubation if it had been > 90% before induction), esophageal intubation, pulmonary aspiration (immediate peri-induction observation of gastric contents), or difficult intubation. Difficult intubation was defined as ≥ three attempts at intubation, airway management of > 10 minutes, or the need for a surgical airway. The authors attempted to control for predicted intubation difficulty by calculating the MACOCHA score, a previously validated score that accounts for Mallampati classification, sleep apnea, cervical mobility, mouth opening, coma, severe hypoxemia, and intubation by a non-anesthesiologist. At the authors’ institutions, an anesthesia trainee or nurse anesthetist and an attending anesthesiologist managed all ward and ICU intubations. For purposes of this study, the authors replaced the term “non-anesthesiologist” with junior operator (anesthesia trainees with < 12 months experience). A MACOCHA score > 3 predicts difficult intubation.
Over a one and a half year period, 528 emergent intubations met criteria for evaluation. Of these, 192 were performed in the head-elevated position. Patients intubated in the head-elevated position were more likely to be intubated by senior operators and were more likely to have a MACOCHA score < 3 (not have a predicted difficult airway). Complications occurred in 18/192 of the head-elevated patients compared to 76/336 of supine patients. This difference was largely driven by more patients in the supine group with hypoxemia (17% vs. 6.3%). After adjusting for MACOCHA score and body mass index, head-elevated position was associated with a lower odds of complications (odds ratio [OR], 0.42; 95% confidence interval [CI], 0.23-0.77; P = 0.005) but not difficult intubation (OR, 0.88; 95% CI, 0.24-3.21; P = 0.848). Results did not change after adjusting for operator experience.
COMMENTARY
The authors’ hypothesis a priori was that the head-elevated position would be associated with a lower risk of complications due to improved visualization and therefore decreased risk of a difficult intubation. Their analysis showed an association between head-elevated position and lower risk of complications, but this was driven primarily by a decreased risk of hypoxemia and not difficult intubation. This is an interesting finding but certainly not definitive, as there are several limitations to this study. The study was retrospective and relied primarily on intubation providers’ self-report of complications. Underreporting of complications is a significant possibility. Interestingly, junior operators were more likely to intubate patients in the supine position than senior operators. Despite attempting to control for operator experience, it is possible that the increased risk of complications was due to operator experience and not patient positioning. At the study’s institutions, professors teach the head-elevated position as the preferred method of intubation unless there are contraindications. However, only about one-third of intubations occurred with the head elevated. The reasons practitioners chose one method over another is not available. Senior operators were far more likely to choose this position but still used this position in less than half of intubations.
The results of this study are not likely to be generalizable to the majority of emergent endotracheal intubations in the ICU. As opposed to many ICUs where intensivists manage the airway, in this study, all practitioners were anesthesiologists. In addition, many of these anesthesiologists were still in training. This study only evaluated patients intubated on the first attempt with direct laryngoscopy. In many ICUs, use of video laryngoscopy is common. A recent meta-analysis reported that in the ICU, video laryngoscopy was associated with a lower risk of difficult intubation and other complications than direct laryngoscopy.1 At the author’s institutions, video laryngoscopy was available, so it is possible that patients assumed to exhibit the most difficult airways were excluded from this study by practitioners choosing to begin with video laryngoscopy.
In summary, patient positioning is often a critical element for a successful endotracheal intubation. In the operating room, the BUHE position appears to have some advantages over the supine position. In the ICU, positioning may even be more important. It was reasonable to assume that the head-elevated position would be associated with decreased complications. However, it is not clear that this has been answered definitely. Further studies should include providers other than anesthesiologists, control for the use of video-laryngoscopy, and use prospective data collection.
REFERENCE
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De Jong A, Molinari N, Conseil M, et al. Video laryngoscopy versus direct laryngoscopy for orotracheal intubation in the intensive care unit: A systematic review and meta-analysis. Intensive Care Med 2014;40:629-639.
