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The TBI SBP Sweet Spot – Is 130-180 mmHg the New Normotension?

August 29, 2022

Written by Seth Walsh-Blackmore

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In-hospital mortality of TBI patients decreased linearly as the lowest observed out-of-hospital systolic blood pressure (SBP) increased, with the lowest mortality between 130 and 180 mmHg.

Why does this matter?
Prior EMS TBI guidelines suggest an SBP threshold of 100-110 mmHg to initiate therapy, with the primary evidence examining SBP as a categorical variable. This study analyzed SBP continuously and demonstrated values typically considered normotensive may undershoot what is optimal.

When they go low, we go high, but not too high…
This was a planned secondary analysis of the EPIC Study dataset, a seven-year statewide prospective before/after observational study of the Arizona EMS system. It included 12,169 isolated or multisystem TBI patients >10 years old transported to level 1 trauma centers. Using a logistic regression analysis adjusted for commonly accepted trauma outcome risk factors and injury scores, the lowest observed out-of-hospital SBP was modeled for the probability of in-hospital mortality.

The probability of death decreased linearly from above 15% to around 11% as the SBP increased from 40 to 130 mmHg. It remained relatively stable between 130 and 180mmHg before sharply increasing above this range (see Figure). Secondary outcomes of ICU length of stay and probability of discharge to a skilled facility followed a similar pattern, with the best outcomes around 130 mmHg. The authors performed sensitivity analyses for mortality by removing penetrating trauma and pediatric patients, with nearly identical curves in each case.

From cited article

Though observational, the size and scope of this dataset and its thorough analysis strengthen the results. The most clinically significant finding is the steady improvement in outcomes far above typical thresholds for hypotension (90 mmHg or even 100-110 mmHg) to initiate out-of-hospital treatment. While maintaining normotension in TBI is not new, these results warrant rethinking the threshold values used to define this before and after hospital arrival. A change in practice warrants a RCT to examine the outcomes of more aggressive BP management. 

Source
Optimal Out-of-Hospital Blood Pressure in Major Traumatic Brain Injury: A Challenge to the Current Understanding of Hypotension. Ann Emerg Med. 2022 Jul;80(1):46-59. doi: 10.1016/j.annemergmed.2022.01.045. Epub 2022 Mar 24.

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