RELATIVE BRADYCARDIA IN PATIENTS WITH TRAUMATIC HYPOTENSION

Background: Tachycardia is considered a physiologic response to trauma tic hypotension. The inability of the heart to respond to shock with t achycardia has been described as paradoxical bradycardia or relative b radycardia, The incidence and clinical significance of this condition in major trauma is not known. The objective of this study was to exami ne the incidence and prognostic significance of tachycardia and relati ve bradycardia in patients with traumatic hypotension. Relative bradyc ardia is defined as a systolic pressure less than or equal to 90 mm Hg and a pulse rate less than or equal to 90 beats per minute. Methods: This is a retrospective study conducted at a large Level I academic tr auma center during a 3-year period. Seventeen demographic and injury s everity factors were analyzed for their possible role in tachycardic o r bradycardic response in hypotensive patients. Incidence and mortalit y were derived for each subpopulation. Bivariate analysis of the assoc iation of incidence and mortality with each risk factor was performed. Factors with p values < 0.2 were included in stepwise logistic regres sion analyses that identified significant risk factors and derived adj usted relative mortality risks between tachycardic and bradycardic hyp otensive patients. Results: Excluding transfers and patients dead on a rrival, 10,833 major trauma patients were seen during the study period , Seven hundred fifty patients (6.9%) had systolic blood pressure less than or equal to 90 mm Hg; 533 patients had tachycardia (overall inci dence of 4.9%, or 71.1% of hypotensive patients), and 217 patients had bradycardia (overall incidence of 2.0%, or 28.9% of hypotensive patie nts), The overall crude mortality was 29.2 % among tachycardia patient s and 21.7% among bradycardia patients (crude relative risk = 1.34; 95 8 confidence interval = 1.00-1.81;p = 0.047), The adjusted relative mo rtality risk between the two groups was 1.23 (95% confidence interval = 0.84-1.73; p = 0.284). Multivariate analysis showed that patients wi th relative bradycardia in the subgroups with Injury Severity Scores g reater than or equal to 16, chest Abbreviated Injury Scale scores grea ter than or equal to 3, or abdominal Abbreviated Injury Scale scores g reater than or equal to 3 had significantly better survival than patie nts with similar injuries presenting with tachycardia, Conclusion: Rel ative bradycardia in hypotensive trauma patients is a common hemodynam ic finding. Mortality among tachycardic patients was more predictable than among bradycardic patients using commonly used demographic and in jury indicators. The presence of relative bradycardia in some subgroup s of patients with severe injuries seems to be associated with better prognosis than the presence of tachycardia.