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

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. 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. 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. Induction with ketamine or propofol as the principal sedative-hypnotic agent. 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. 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.