SAN DIEGO (FRONTLINE MEDICAL NEWS) In the setting of traumatic brain injury, increases in systolic blood pressure after the nadir are independently associated with improved survival in hypotensive patients.

In addition, even substantial blood pressure increases do not seem to harm normotensive patients. These findings come from a subanalysis of the ongoing National Institutes of Health–funded Excellence in Prehospital Injury Care (EPIC) TBI study .

“Very little is known about the patterns of blood pressure in traumatic brain injury in the field,” principal investigator Dr. Daniel W. Spaite said at the annual meeting of the National Association of EMS Physicians. “For instance, nobody knows whether it’s better to have your blood pressure increasing, stable, or decreasing in the field with regard to outcome, especially mortality. Typical studies that do have EMS data linked only have a single blood pressure measurement documented, so there’s no knowledge of trends in EMS blood pressure in TBI.”

Dr. Spaite, professor and Virginia Piper Endowed Chair of Emergency Medicine at the University of Arizona, Tucson, and his colleagues evaluated the association between mortality and increases in prehospital systolic blood pressure after the lowest recorded measurement in major TBI patients who are part of the EPIC study – the statewide implementation of TBI guidelines from the Brain Trauma Foundation and the NAEMSP. Data sources include the Arizona State Trauma Registry, which has comprehensive hospital outcome data. “The cases are then linked and the EMS patient care reports are carefully abstracted by the EPIC data team,” Dr. Spaite explained. “This included major TBI (which is, clinically, both moderate and severe) and all patients whose lowest systolic BP was between 40 and 300 mm Hg.”

The researchers used logistic regression to examine the association between the increase in EMS systolic blood pressure (SBP) after the lowest EMS blood pressure and its association with adjusted probability of death. They then partitioned the study population into four cohorts based on each patient’s prehospital systolic BP (40-89 mm Hg, 90-139 mm Hg, 140-159 mm Hg, and 160-300 mm Hg). In each cohort, they identified the independent association between the magnitude of increase in SBP and the adjusted probability of death.

Dr. Spaite reported findings from 14,567 TBI patients. More than two-thirds (68%) were male, and their mean age was 45 years. The researchers observed that, in the hypotensive cohort, mortality dropped significantly if the SBP increased after the lowest SBP. “Improvements were dramatic with increases of 40-80 mm Hg,” he said. In the normotensive group, increases in SBP were associated with very slight reductions in mortality. Even large increases in SBP, such as in the range of 70-90 mm Hg, did not appear to be detrimental.

In the mildly hypertensive group, large systolic increases were associated with higher mortality. “Interestingly, even if your lowest [SBP] is between 140 and 159 mm Hg, until you get above an increase of 40 mm Hg above that, you don’t start seeing increases in mortality,” Dr. Spaite said. In the severely hypertensive group, mortality was higher with any subsequent increase in SBP, “which doesn’t surprise any of us,” he said. “It’s dramatically higher if the increase is large.”

Dr. Spaite emphasized that the current analysis is based on observational data, “so this does not prove that treating hypotension improves outcome. … That direct question is part of the EPIC study itself and awaits the final analysis, hopefully in mid-2017. This is the first large report of blood pressure trends in the prehospital management of TBI.”

He concluded that the current findings in the hypotensive and normotensive cohorts “support guideline recommendations for restoring and optimizing cerebral perfusion in EMS traumatic brain injury management. What is fascinating about the literature is that the focus in TBI has always been on hypotension, but there’s very little information about what’s the best or the optimal blood pressure.”

EPIC is funded by the National Institutes of Health. Dr. Spaite reported having no relevant financial disclosures.