Prehospital invasive arterial blood pressure monitoring in critically ill patients attended by a UK Helicopter Emergency Medical Service – a retrospective observational review of practice

Abstract

Background Accurate haemodynamic monitoring of critically unwell and injured patients in the prehospital setting is essential. Non-invasive blood pressure measurement is susceptible to vibration and motion artefact, especially at extremes of hypotension and hypertension. Invasive arterial blood pressure (IABP) monitoring is a potential solution to these limitations. The aim of this study was to describe the largest series to date of patients in whom IABP monitoring was successfully initiated prehospital. Methods This retrospective observational study was conducted at East Anglian Air Ambulance, a UK helicopter emergency medical service (HEMS) which provides prehospital critical care in the East of England. It included all patients attended by EAAA who underwent arterial catheterisation and initiation of IABP monitoring between 1st February 2015 and 20th April 2023. The following data were retrieved for all patients: sex; age; aetiology (medical cardiac arrest, other medical emergency, trauma); site of arterial cannulation; operator role (doctor/paramedic); the time of insertion and, where applicable, time of pre-hospital emergency anaesthesia, and return of spontaneous circulation following cardiac arrest. Characteristics of the sample were described as number (percentage) for categorical variables and mean (± standard deviation (SD)) or median (interquartile range = IQR) for continuous variables as appropriate. Results During the study period 13,556 patients were attended; IABP monitoring was initiated in 1083 (8.0%) cases (70.8% male; median age 59 years). 546 cases (50.4%) were of medical cardiac arrest: in 22.4% of these IABP monitoring was initiated during cardiopulmonary resuscitation. 322 (29.7%) were trauma cases, and the remaining 215 (19.9%) were medical emergencies. The patients were critically unwell: 981 (90.6%) required intubation, of which 789 (72.6%) underwent prehospital emergency anaesthesia; 609 (56.2%) received vasoactive medication. In 424 (39.2%) cases IABP monitoring was instituted en route to hospital. Conclusions This study describes over 1000 cases of prehospital arterial catheterisation and invasive blood pressure monitoring in a UK HEMS system and has demonstrated feasibility at scale with no clear signal of catheter-associated complications. The high-fidelity of invasive arterial blood pressure monitoring with the additional benefit of arterial blood gas analysis presents an attractive translation of in-hospital critical care to the prehospital setting.