Mortality and Prehospital Blood Pressure in Patients With Major Traumatic Brain Injury

Abstract

Importance Current prehospital traumatic brain injury guidelines utilize a systolic blood pressure threshold of <90mmHg for treating hypotension (age≥10) based on studies showing higher mortality when blood pressure drops below this level. However, the guidelines also acknowledge the weakness of the supporting evidence. Objective In a statewide, multisystem study of traumatic brain injury, to evaluate whether any statistically supportable systolic pressure-versus-mortality threshold emerges from the data, a priori, without assuming that a cut-point exists. Design Observational evaluation of a large prehospital database established as a part of the Excellence in Prehospital Injury Care (EPIC) Traumatic Brain Injury Study (NIH/NINDS-1R01NS071049). The generalized additive model and logistic regression were utilized to determine the relationship between systolic pressure and probability of death, adjusting for significant/important confounders. Setting The pre-implementation cohort (1/1/2007–3/31/2014) of the EPIC Study. Participants Patients (age≥10) with moderate/severe traumatic brain injury (Barell Matrix-Type 1 and/or International Classification of Disease-9 head region severity ≥3 and/or Abbreviated Injury Scale head-region severity ≥3) and lowest prehospital systolic pressure between 40 and 119mmHg were included. Main Outcome Measure The main outcome measure was in-hospital mortality. Results Among the 3,844 included cases, the model revealed a monotonically-decreasing relationship between systolic pressure and adjusted probability of death across the entire range (40–119mmHg). Each ten-point increase of systolic pressure was associated with a decrease in the adjusted odds of death of 18.8% (aOR=0.812; 95% confidence interval: 0.748–0.883). Thus, the adjusted odds of mortality increase as much for a drop from, say, 110 to 100mmHg as for 90 to 80mmHg, and so on, throughout the range. Conclusions and Relevance We found a linear relationship between lowest prehospital systolic blood pressure and severity-adjusted probability of mortality across an exceptionally wide range. There is no identifiable threshold or inflection point between 40 and 119mmHg. Thus, in traumatic brain injury, the concept that 90mmHg represents a unique or important physiological “cut-point” may be wrong. Furthermore, clinically-meaningful “hypotension” may not be as low as current guidelines suggest. Randomized trials evaluating treatment levels significantly above 90mmHg are needed.

Identification of Serious Adverse Events in Patients with Traumatic Brain Injuries, from Prehospital Care to Intensive-Care Unit, Using Early Warning Scores

“…The identification in a prehospital setting of TBIs with a high risk of deterioration is directly influenced by the early detection of the two physio-pathological situations causing most morbimortality, hypoxia and hypotension [40,41]. Advanced airway management at the scene [42] using orotracheal intubation in those TBIs with a low GCS score, presence of convulsions, agitation, or in case of situations with other associated trauma, is a recognized practice approved by current brain injury treatment guides [43,44].…”

Association of Out-of-Hospital Hypotension Depth and Duration With Traumatic Brain Injury Mortality

“…We plan to use the post-implementation cases not only to validate the current findings but also to identify alternate functional forms with clearer improvement of the dosage-based model over binary hypotension. For instance, since our previous work revealed a complete absence of an identifiable physiological threshold anywhere between an SBP of 40 and 120 mmHg, 35 the discriminatory power of the model may improve when hypotension is defined as <100, <110, or <120 mmHg. 53 Furthermore, when higher thresholds are evaluated, comparing the binary model versus the dose-based model in the overall study cohort will be pertinent since such a comparison will be much less likely to be dominated by the non-hypotensive subgroup.…”

“…33–35 EPIC is evaluating the impact of implementing the EMS TBI guidelines 36–39 in patients with major TBI throughout Arizona using a before-after, controlled, multisystem, observational design 33 (ClinicalTrials.gov #NCT01339702). We obtained the necessary regulatory approvals for EPIC from the Arizona Department of Health Services (ADHS) and the State Attorney General.…”

“…33–35 The ASTR has detailed in-hospital data on all trauma patients taken to the state-designated level I TCs in Arizona. All cases from the ASTR that meet EPIC criteria are entered into the database.…”

“…Trauma type (blunt versus penetrating), payment source, and treating TC were included because they have often been confounders in trauma outcome studies 44,45 and were found to be significant covariates in previous EPIC reports. 34,35 …”