Linear association found between low blood pressure and TBI

Doctors are thinking differently about blood pressure in patients with a serious brain injury thanks to a new study that found a linear association between lowest prehospital systolic blood pressure and severity-adjusted probability of mortality – across the whole range of pressures between 40 and 120 mmHg. “For patients with acute traumatic brain injury (TBI), […]

Doctors are thinking differently about blood pressure in patients with a serious brain injury thanks to a new study that found a linear association between lowest prehospital systolic blood pressure and severity-adjusted probability of mortality – across the whole range of pressures between 40 and 120 mmHg.

“For patients with acute traumatic brain injury(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,” an article about the study posted to the MedScape website reads. “The researchers note these findings, which were   published online   December 7 in   JAMA Surgery , show that for the injured brain, physiologically detrimental hypotension may occur at significantly higher blood pressure levels than current guidelines advise.”

The researchers said their findings highlight the need for specific trials comparing various blood pressure treatment thresholds well above the classic 90 mmHg.

“This data really changes how we think about blood pressure in patients with a serious brain injury in an acute setting. This is a major paradigm shift,” study coauthor, Joshua Gaither, MD, associate professor of emergency medicine, College of Medicine, University of Arizona, Tucson, told   Medscape Medical News .

“Historically we have been taught that when considering blood pressure in the setting of acute traumatic brain injury there is a magic number of 90 and as soon as the pressure is below 90 mmHg then damage will occur. We show in this study that this is not the case and for patients with systolic pressures anywhere between 40 and 120 mmHg, mortality rises as blood pressure falls. There is no magic cutoff. This suggests we need to treat blood pressure aggressively across a larger spectrum than previously thought,” he added.

TBI causes two types of damage: the primary injury — the damage to the brain when the head is hit — which is thought to be irreversible, and secondary damage caused by the injured brain being extra susceptible to secondary insults, such as low blood pressure.

“Because this is observational data we cannot say for sure that raising blood pressure will reduce mortality in these patients. But it does show that the lower the blood pressure, the more likely a patient is to die,” Gaither said in the article. “We really need a randomized trial to investigate whether more aggressive treatment with fluids does make a difference in terms of mortality in patients at all levels of blood pressure.”