Severe Traumatic Brain Injury and Controlled Hemorrhage in Rats

Abstract

Treatment of combined traumatic brain injury and hypovolemic shock poses a particular challenge due to the possible conflicting consequences. While restoring diminished volume is the treatment goal for hypovolemia, maintaining and adequate cerebral perfusion pressure and avoidance of secondary damage remain a treatment goal for the injured brain. Various treatment modalities have been proposed, but the optimal resuscitation fluid and goals have not yet been clearly defined. In this study, we investigate the physiological and neurological outcomes in a rat model of combined traumatic brain injury and hypovolemic shock, submitted to treatment with varying amounts of fresh blood. Forty-eight male Lewis rats were divided into control and treatment groups. Traumatic brain injury was inflicted by a free-falling rod on the exposed cranium. Hypovolemia was induced by controlled hemorrhage of 30% blood volume. Treatment groups were treated by fresh whole blood with varying volumes, reaching resuscitation goals of a mean arterial blood pressure (MAP) of 80, 100, and 120 mmHg at 15 min. Mean arterial blood pressure was assessed at 60 min and neurological outcomes and mortality in the subsequent 48 h. At 60 min, MAP was highest for the group resuscitated most aggressively. Neurological outcomes and mortality inversely correlated with the aggressiveness of resuscitation. In this study, we find that mild resuscitation with goals of restoring MAP to 80 mmHg (which is lower than baseline) provided best results when considering hemodynamic stability, survival, and neurological outcomes. An aggressive resuscitation may be detrimental, inducing processes that eventually cause a significant decrease in survival.