Hypotension is 100 mm Hg on the battlefield

Abstract

Background Historically, emergency physicians and trauma surgeons have referred to a systolic blood pressure (SBP) of 90 mm Hg as hypotension. Recent evidence from the civilian trauma literature suggests that 110 mm Hg may be more appropriate based on associated acidosis and outcome measures. In this analysis, we sought to determine the relationship between SBP, hypoperfusion, and mortality in the combat casualty. Methods A total of 7,180 US military combat casualties from the Joint Theater Trauma Registry from 2002 to 2009 were analyzed with respect to admission SBP, base deficit, and mortality. Base deficit, as a measure of hypoperfusion, and mortality were plotted against 10-mm Hg increments in admission SBP. Results By plotting SBP, baseline mortality was less than 2% down to a level of 101 to 110 mm Hg, at which point the slope of the curve increased dramatically to a mortality rate of 45.1% in casualties with an SBP of 60 mm Hg or less but more than 0 mm Hg. A presenting SBP of 0 mm Hg was associated with 100% mortality. The data also established a similar effect for base deficit with a sharp increase in the rate of acidosis, which became manifest at an SBP in the range of 90 to 100 mm Hg. Conclusions This analysis shows that an SBP of 100 mm Hg or less may be a better and more clinically relevant definition of hypotension and impending hypoperfusion in the combat casualty. One utility of this analysis may be the more expeditious identification of battlefield casualties in need of life-saving interventions such as the need for blood or surgical intervention.