Protocol for a multicentre target trial emulation comparing ketamine and propofol in critically ill adults undergoing emergency intubation

Background: Emergency intubation in the critically ill adults is frequently complicated by haemodynamic instability and severe hypoxaemia. Ketamine and propofol are widely used for induction, yet high-quality comparative effectiveness evidence in real-world emergency department, medical ward, and intensive care unit (ICU) settings remains limited. Objective: To estimate the causal effect of ketamine versus propofol as the principal induction agent for emergency intubation in critically ill adults and using a target trial emulation framework with competing risks survival analysis. Design setting and participants: A retrospective multicentre cohort across the Monash Health network, emulating a hypothetical randomised trial. Adults (≥18 years) undergoing unplanned endotracheal intubation in the emergency department, medical ward, or ICU with subsequent ICU admission will be included. Intervention: Induction with ketamine or propofol as the principal sedative-hypnotic agent. Main outcome measures: Primary outcome will be in-hospital mortality, assessed from induction until death, hospital discharge, or 28 days, whichever occurs first. The secondary outcomes will be a composite peri-intubation adverse event, defined as haemodynamic collapse or severe hypoxaemia within 30 min of intubation. Conclusion: This target trial emulation will provide real-world causal evidence comparing ketamine versus propofol induction for high-risk emergency intubation, with the potential to inform practice, protocols, and future randomised trials.