Aims and Objectives Background: Prehospital Emergency Anaesthesia (PHEA) is crucial in managing critically ill patients in the prehospital environment. Many past studies measure first pass success (FPS) as a proxy marker for procedural success, few have investigated the physiological challenges such as hypotension, hypoxia, or cardiac arrest which are arguably more important to patient outcome. This study aimed to identify factors associated with these complications and develop a predictive model to mitigate these in future.

Method and Design Using data from the North West Air Ambulance (NWAA) service, a retrospective service evaluation was conducted exploring patient and procedural factors affecting adverse events post-PHEA. A composite outcome variable of hypotension (>20% drop in systolic blood pressure SBP) or SBP<90mmHg), hypoxia (>10% drop in SpO2 or SpO2 <90%), or cardiac arrest was created. Patient demographics (age, weight, gender), injury mechanism, indication for PHEA and intubation details for patients who received PHEA between 18th March 2022 and 1st May 2024 were retrieved from HEMSbase and collated into a password-protected data sheet. Physiological data (heart rate (HR), SBP and respiratory rate (RR)) was extracted manually. A binary logistic regression model was then developed using SPSS statistical software to identify predictors associated with adverse events post-PHEA.

Results and Conclusion Results: During the study period, 3,128 patients were attended, 344 underwent PHEA and 294 were included in the final analysis. 47.3% of patients experienced an adverse event, most commonly hypotension. On multivariate analysis, increasing age was the only independent predictor (p<0.001) however the presence of airway soiling was found to have the largest effect size on the outcome (Exp(B) = 1.202, p=0.472). The investigated variables accounted for only a small proportion of the observed outcome (Nagelkerke R Square = 0.079).

Conclusion: Increasing age was significantly associated with experiencing an adverse event. Further research is required to investigate the other factors influencing patient outcomes post-PHEA.