For patients with traumatic brain injury, even a brief drop in blood pressure can reduce blood flow to the brain. Clinicians aim to keep systolic blood pressure above 110 mmHg to protect brain tissue, especially during interventions like PHEA.

However, the process of giving anaesthesia can itself trigger sudden changes in blood pressure. Continuous invasive blood pressure (IBP) monitoring allows rapid detection and treatment of these changes — something that may not be possible with cuff readings taken only every few minutes.

KSS clinical teams have used arterial line blood pressure monitoring since 2022 when the lifesaving charity became one of the first UK air ambulance services to introduce this intervention. Today, around half of the UK air ambulance charities are able to monitor blood pressure continuously in this way.

The new study from the Research and Innovation team at KSS, examined 140 patients with suspected TBI who were treated between January 2022 and July 2024. All patients in the study received continuous IBP monitoring before undergoing PHEA, allowing clinicians to track blood pressure changes every second rather than every few minutes.

Key Findings

• Low blood pressure was more common than previously recognised:
  Only 9.3% of patients had absolute hypotension before PHEA, but this rose to 37.9% after PHEA.
• Many episodes were brief but important:
  Over half of post-PHEA episodes lasted fewer than five minutes, with almost a quarter lasting under one minute. These short events may go undetected when relying on standard non-invasive cuffs.
• Continuous monitoring captured changes that conventional methods could miss:
  Previous studies using intermittent blood pressure cuffs reported far lower rates of hypotension. Continuous IBP revealed more frequent but shorter episodes—highlighting how easily these events can be overlooked.
• Patients already showing low or borderline blood pressure before anaesthesia were more likely to become hypotensive afterwards — suggesting that early recognition and proactive treatment may help reduce risk.

KSS Paramedic Silas Houghton, lead author of the study, said: “Our findings show that short, hidden episodes of low blood pressure are far more common than we previously knew — and that they may occur at exactly the moment when the brain is most vulnerable.

“This research demonstrates how our commitment to innovation directly benefits patients. By using advanced monitoring, our clinical teams can tailor treatment more effectively and give patients with devastating injuries the best possible chance of survival.”

Next Steps

KSS continues to evaluate how innovative monitoring techniques can improve patient outcomes. The KSS Research and Innovation Team is calling for further studies that link IBP data with long-term patient outcomes. Understanding not just if hypotension occurs, but how long it lasts and how severe it is, could help shape future national guidelines for caring for people with traumatic brain injury.