Anesthetic induction drugs during tracheal intubation in critically ill patients: a systematic review

Induction of anesthesia in patients with unstable hemodynamics presents a major challenge for anesthesiologists; however, evidence to guide optimal practice remains limited. Although recent studies recommend etomidate and ketamine for tracheal intubation, etomidate may cause adverse effects such as adrenal insufficiency. Therefore, this systematic review evaluated the relationship between commonly used induction agents other than etomidate-including ketamine and midazolam-and the incidence of post-induction hypotension.

We systematically searched the PubMed and Cochrane Library databases from inception through March 16, 2025. Eligible studies included randomized controlled trials and observational studies involving critically ill adults undergoing emergency tracheal intubation. We compared induction agents including ketamine, fentanyl, midazolam, remimazolam, propofol, thiopental, and placebo or saline. The primary outcome was post-induction hypotension.

A total of 1,063 articles were identified during the initial screening, and nine met the inclusion criteria. Owing to marked heterogeneity in study design and drug comparisons, meta-analysis was not feasible. Reported incidence of post-induction hypotension varied widely (6-84%), reflecting differences in patient case mix, drug regimens, and definitions of hypotension. Definitions of hypotension and observation periods also differed across studies.

This review found limited evidence on the hemodynamic effects of anesthetic agents other than etomidate during tracheal intubation in critically ill patients. Standardized definitions and high-quality research are needed to better characterize post-induction hypotension and determine the safest anesthetic combinations.