Rapid sequence intubation (RSI) is the standard approach for emergency airway management in critically ill patients requiring endotracheal intubation. Laryngoscopy and tracheal intubation may provoke significant hemodynamic responses, including increases in heart rate and blood pressure, which may adversely affect patients with severe neurological or cardiovascular disease.

Although hemodynamic responses during tracheal intubation have been extensively investigated in the anesthesiology literature, evidence from emergency department settings remains limited. Furthermore, previous studies have rarely confirmed whether an adequate depth of anesthesia had been achieved before laryngoscopy, making interpretation of hemodynamic responses difficult.

The aim of this prospective observational study is to evaluate hemodynamic responses during rapid sequence intubation in adult emergency department patients after confirming adequate depth of anesthesia using bispectral index (BIS) monitoring. Heart rate and blood pressure will be recorded before induction, during intubation, and after successful endotracheal intubation, allowing objective assessment of the hemodynamic response under confirmed adequate anesthetic depth.