OBJECTIVE:
To describe paroxysmal sympathetic hyperactivity in pediatric patients with severe traumatic brain injury using the new consensus definition, the risk factors associated with developing paroxysmal sympathetic hyperactivity, and the outcomes associated with paroxysmal sympathetic hyperactivity.

DESIGN:
Retrospective cohort study.

SETTING:
Academic children's hospital PICU.

PATIENTS:
All pediatric patients more than 1 month and less than 18 years old with severe traumatic brain injury between 2000 and 2016. We excluded patients if they had a history of five possible confounders for paroxysmal sympathetic hyperactivity diagnosis or if they died within 24 hours of admission for traumatic brain injury.

MEASUREMENTS AND MAIN RESULTS:
Our primary outcome was PICU mortality. One hundred seventy-nine patients met inclusion criteria. Thirty-six patients (20%) had at least eight criteria and therefore met classification of "likelihood of paroxysmal sympathetic hyperactivity." Older age was the only factor independently associated with developing paroxysmal sympathetic hyperactivity (odds ratio, 1.08; 95% CI, 1.00-1.16). PICU mortality was significantly lower for those with paroxysmal sympathetic hyperactivity compared with those without paroxysmal sympathetic hyperactivity (odds ratio, 0.08; 95% CI, 0.01-0.52), but PICU length of stay was greater in those with paroxysmal sympathetic hyperactivity (odds ratio, 4.36; 95% CI, 2.94-5.78), and discharge to an acute care or rehabilitation setting versus home was higher in those with paroxysmal sympathetic hyperactivity (odds ratio, 5.59; 95% CI, 1.26-24.84; odds ratio, 5.39; 95% CI, 1.87-15.57, respectively). When paroxysmal sympathetic hyperactivity was diagnosed in the first week of admission, it was not associated with discharge disposition.

CONCLUSIONS:
Our study suggests that the rate of paroxysmal sympathetic hyperactivity in patients with severe traumatic brain injury is higher than previously reported. Older age was associated with an increased risk for developing paroxysmal sympathetic hyperactivity, but severity of the trauma and the brain injury were not. For survivors of severe traumatic brain injury beyond 24 hours who developed paroxysmal sympathetic hyperactivity, there was a lower PICU mortality but also greater PICU length of stay and a lower likelihood of discharge home from the admitting hospital, suggesting that functional outcome in survivors with paroxysmal sympathetic hyperactivity is worse than survivors without paroxysmal sympathetic hyperactivity.