Bispectral Index and First-Pass Intubation

Endotracheal intubation is a life-saving intervention frequently performed in the emergency department for patients with airway compromise, respiratory failure, or critical illness. Despite its importance, emergency airway management is associated with a substantial risk of adverse events. Previous studies have consistently demonstrated that multiple intubation attempts significantly increase the likelihood of hypoxemia, aspiration, hypotension, cardiac arrest, airway trauma, and mortality. Therefore, achieving first-pass success has become one of the principal quality indicators in emergency airway management.

Several patient-, operator-, and procedure-related factors influence first-pass success, including anatomical difficulty, operator experience, type of laryngoscope, choice of sedative and neuromuscular blocking agents, and optimization of preoxygenation. Another potentially important but understudied factor is the depth of anesthesia at the moment of laryngoscopy and intubation.

Adequate anesthetic depth before laryngoscopy suppresses airway reflexes, minimizes patient movement, and improves intubating conditions. Previous studies comparing succinylcholine and rocuronium have suggested differences in intubation conditions; however, subsequent investigations demonstrated that these differences were largely attributable to dosing strategies rather than the neuromuscular blocking agent itself. Current evidence indicates that when appropriate doses are administered, both agents provide comparable intubating conditions. Nevertheless, regardless of the neuromuscular blocking agent used, insufficient hypnotic depth may adversely affect intubation conditions.

The Bispectral Index (BIS) is a processed electroencephalographic parameter ranging from 0 to 100 that provides an objective assessment of the patient's level of consciousness. BIS monitoring has been extensively validated in the operating room and has demonstrated a strong correlation with anesthetic depth. Randomized clinical trials have shown that BIS-guided anesthesia reduces the incidence of intraoperative awareness and may facilitate individualized anesthetic administration. However, BIS monitoring is not routinely incorporated into emergency airway management, and limited evidence exists regarding its relationship with first-pass intubation success in emergency department patients.

This study is designed as a prospective observational study. Adult patients undergoing rapid sequence intubation after a clinical decision by the treating emergency physician will be consecutively enrolled. A disposable BIS sensor will be placed on the patient's forehead immediately before induction, and BIS monitoring will be performed continuously. The emergency physician performing the intubation will remain blinded to the BIS values throughout the procedure. A separate investigator, independent of clinical management, will record the BIS value at the time of laryngoscopy and intubation.

Importantly, BIS measurements will not be communicated to the treating physician and will not influence the timing of intubation, medication selection, medication dosing, or any other aspect of patient care. Therefore, this investigation is not intended to evaluate or validate the BIS device as a medical device intervention. Rather, BIS is used solely as a noninvasive measurement tool to objectively quantify anesthetic depth. The monitor consists of a disposable adhesive forehead sensor and poses minimal risk to participants.

The primary analysis will compare BIS values between patients with successful first-pass intubation and those requiring more than one intubation attempt. The study seeks to determine whether inadequate anesthetic depth is associated with failure of first-pass intubation. The findings may improve understanding of the role of anesthetic depth during emergency airway management and may contribute to strategies aimed at increasing first-pass success while reducing intubation-related complications.