For patients with TBI, the higher the prehospital systolic blood pressure the better — a finding that challenges the conventional wisdom that there is a clinically meaningful threshold, new research suggests. The study — the largest to date to look at this issue — found a linear association between lowest prehospital systolic blood pressure and severity-adjusted probability of mortality. The researchers note these findings, published in JAMA Surgery, show that for the injured brain, physiologically detrimental hypotension may occur at significantly higher blood pressure levels than current guidelines advise.
For the study, the researchers analyzed information from a large prehospital database established as a part of the Excellence in Prehospital Injury Care (EPIC) Traumatic Brain Injury Study to determine the association between systolic pressure and probability of death, adjusting for significant/important confounders. The study included 3844 patients age 10 years and older with moderate or severe TBI and a prehospital systolic pressure between 40 and 119 mmHg. Results revealed a linear decreasing association between systolic pressure and adjusted probability of death across the entire blood pressure range. Each 10-point increase of systolic pressure was associated with a decrease in the adjusted odds of death of 18.8%. The researchers point out that a key reason for evaluating the effect of blood pressure measured before hospital arrival is that the injured brain is so highly sensitive to changes in perfusion and the timeframe during which neuronal damage begins is so short.