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.