Aims, Objectives and Background Prehospital emergency anaesthesia (PHEA) is a safe and necessary procedure for the most seriously injured trauma patients. The avoidance of secondary insults such as hypoxia and hypotension are key to reduce mortality. Despite this, a proportion of patients experience post-intubation hypotension (PIH), for which the determinants remain unclear. This multi-centre study aims to compare the differential determinants of PIH in trauma patients undergoing PHEA.

Method and Design In this retrospective observational study, across three regional Helicopter Emergency Medical Services (HEMS), data were obtained from the electronic medical records for a consecutive sample of adult trauma patients who underwent PHEA, 2015–2020 inclusive.

Hypotension was defined as new systolic blood pressure (SBP) <90mmHg or >10% drop if SBP<90mmHg pre-PHEA, within 10 minutes of PHEA. A purposeful selection logistic regression model was used. Each variable was first tested in turn to explore the unadjusted association with the outcome. Significant variables were then included in the multivariable analysis. Variables were successively eliminated until only statistically significant variables remained. The ARU Research Ethics Panel granted ethical approval (AH-SREP-20–047).

Results and Conclusion During the study period, 6184 patients were identified. After predefined exclusions, 998 patients were included in the final analysis. 218 (21.8%) patients recorded one or more episodes of PIH, with a peak prevalence at 8 minutes. The variables significantly associated with PIH were: age >55 years, pre-PHEA tachycardia (>100/minute), fluid administration prior to HEMS arrival, and fentanyl omission at induction, table 1.

The pseudo-R2 for the final model suggests there is significant variation in the outcome not explained by the captured variables alone. Clinician gestalt appears to successfully identify patients most at-risk of PIH, demonstrated by the omission of fentanyl for this group.

In addition to drug-dose modification, pre-PHEA volume administration, cautious haemodynamic observation, and early vasopressor intervention may be warranted to reduce avoidable harm in trauma patients undergoing PHEA.