Clinical Factors Associated With Early Ketamine Initiation Among Mechanically Ventilated Adults: A Retrospective MIMIC‐IV Cohort Study
Mary Ivasyutyn, Gaurav Prabhu, Saajan BhaktaIntroduction
Ketamine is used for analgesia and sedation in mechanically ventilated ICU patients; however, the clinical factors associated with its early initiation remain poorly characterised.
Methods
We conducted a retrospective cohort study using the Medical Information Mart for Intensive Care IV Version 3.1 among adults receiving invasive mechanical ventilation and continuous first‐line sedation with propofol, dexmedetomidine or midazolam. Early ketamine was defined as recorded administration by a continuous infusion or medication push within 48 h after qualifying first‐line sedation began. Concurrent ventilation or continued first‐line sedation was not required. Associations were assessed using multivariable logistic regression with patient‐clustered robust standard errors.
Results
Among 24,363 qualifying ICU stays in 22,396 patients, 226 stays (0.9%) met the early‐ketamine definition. The primary complete‐case analysis included 21,342 stays and 196 early‐ketamine events. Surgical/trauma intensive care unit admission (adjusted odds ratio 2.05, 95% confidence interval 1.39–3.04; p < 0.001), Black race (adjusted odds ratio 1.63, 95% confidence interval 1.05–2.53; p = 0.028) and Stage 3 acute kidney injury (adjusted odds ratio 1.67, 95% confidence interval 1.10–2.53; p = 0.016) were associated with higher odds of early ketamine initiation. Cardiac ICU admission and higher P/F ratio were associated with lower odds. Mean PEEP showed a nonlinear association ( p = 0.005). Of 226 starts, 165 (73.0%) occurred during recorded invasive ventilation. Estimates were similar after bolus exclusion, whereas restricting initiation to recorded ventilation attenuated several associations, including surgical/trauma ICU admission (adjusted odds ratio 1.49; 95% CI, 0.97–2.31).
Discussion
Early ketamine administration was uncommon under the study definition and did not always begin during recorded invasive ventilation. Associations were similar after bolus exclusion, but some attenuated when initiation was restricted to recorded ventilation. These findings describe patterns of ketamine use and do not establish treatment indications or therapeutic benefits.