The incidence of dysautonomia and its relationship with autonomic arousal following traumatic brain injury

Primary objective: To determine the incidence of autonomic arousal vs. Dysautonomia following traumatic brain injury ( TBI) in an Intensive Care Unit ( ICU) setting and to prospectively evaluate these groups against injury severity and outcome variables. Research design: Prospective observational group comparison (cohort) study of consecutive ICU admissions to a major trauma hospital over a 2-year period. Main outcomes and results: Eighty-nine of 113 subjects met inclusion and exclusion criteria, with consent gained for 79 subjects ( 61 male, 18 female: 89% of potential subjects). During the first 7 days post-injury, elevated autonomic parameters were almost universal in the sample ( 92%), predominantly hypertension and tachycardia. Nineteen of 79 subjects ( 24%) were autonomically aroused on day 7 ( that is, had elevated heart rate, respiratory rate, blood pressure and temperature). Dysautonomia was diagnosed on day 14 post-injury in six of 79 subjects ( 8%) using previously published criteria. Autonomically aroused subjects had significantly more severe injuries, poorer outcomes and greater estimated costs than non-aroused subjects. Furthermore, Dysautonomic subjects within the autonomically aroused group had significantly worse outcome and, excluding early deaths, a greater period of hospitalization and higher estimated costs. Conclusions: The 8% incidence of Dysautonomia during ICU admission was in broad agreement with previous research. While day 7 autonomic arousal indicated a greater degree of injury, the diagnosis of Dysautonomia provided additional prognostic information. A coordinated multi-centre research effort into this condition appears appropriate.