Resuscitation with pressors after traumatic brain injury

BACKGROUND: The purpose of the study was to compare initial resuscitation with arginine vasopressin (AVP), phenylephrine (PE), or isotonic crystalloid fluid alone after traumatic brain injury and vasodilatory shock. STUDY DESIGN: Anesthetized, ventilated swine (n = 39, 30 ± 2 kg) underwent fluid percussion traumatic brain injury followed by hemorrhage (30 ± 2mL/kg) to a mean arterial pressure < 30mmHg, then were randomized to 1 of 5 groups to maintain mean arterial pressure > 60mmHg for 30 to 60minutes, then cerebral perfusion pressure > 60mmHg for 60 to 300minutes, either unlimited crystalloid fluid only (n = 9), arginine vasopressin + fluid (n = 9), phenylephrine + fluid (n = 9), arginine vasopressin only (n = 5), or phenylephrine only (n = 5). Heterologous transfusions were administered if hematocrit was < 13, and mannitol was administered if intracranial pressure was > 20 mmHg. Cerebrovascular reactivity was evaluated with serial CO ₂ challenges. RESULTS: In all groups, physiologic variables were similar at baseline and at the end of shock. On resuscitation, all achieved mean arterial pressure and cerebral perfusion pressure goals. Brain tissue PO ₂s were similar. With fluid only, more blood and mannitol were required, intracranial pressure and peak inspiratory pressure were higher, and cerebrovascular reactivity was decreased (all p < 0.05 versus pressor + fluid). With either pressor + fluid, cardiac output, heart rate, lactate, and mixed venous O₂ saturation were similar to fluid only, but total fluid requirements and urine output were both reduced (p < 0.05). With either pressor only, intracranial pressure remained low, but mixed venous O ₂ saturation, cardiac output, and urine output were decreased (all p < 0.05 versus other groups). CONCLUSIONS: To correct vasodilatory shock after traumatic brain injury, a resuscitation strategy that combined either phenylephrine or arginine vasopressin plus crystalloid was superior to either fluid alone or pressor alone.