Acute ethanol intoxication in a model of traumatic brain injury with hemorrhagic shock: effects on early physiological response

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Abstract
Traumatic brain injury (TBI) is exacerbated by hypotension and hypoventilation. Because previous studies have shown a potentiating effect of ethanol (EtOH) on TBI and hemorrhagic shock (HS), the authors investigated the effects of EtOH on the early physiological response to TBI with and without HS. Anesthetized swine, weighing approximately 20 kg each, underwent fluid-percussion TBI of 3 atm with or without 30 ml/kg hemorrhage for a period of 30 minutes. The mean arterial blood pressure, intracranial pressure, cerebral perfusion pressure (CPP), cardiac output, cerebral venous oxygen saturation, and metabolic parameters were monitored for 3 hours postinjury. Ventilation and the response to hypercapnia were also measured. Regional cerebral blood flow and renal blood flow were measured using dye-labeled microspheres. Five groups were studied: control, TBI, TBI/EtOH, TBI/HS, and TBI/HS/EtOH. The EtOH (3.5 g) was given intragastrically 100 minutes preinjury. The TBI/HS/EtOH group demonstrated a 3-hour mortality rate of 56% and postinjury apnea requiring ventilation in 44% of animals compared with 0% in all other groups. Minute ventilation and the hypercapnic ventilatory response were significantly reduced in the postinjury period in the TBI/HS/EtOH group. The animals in this group had significantly lower CPP and cardiac output in the first 60 minutes postinjury, as well as lower renal and cerebral blood flow. Postinjury cerebral venous lactate levels were higher, and cerebral venous pH was lower in the TBI/HS/EtOH group. In this model of TBI, acute EtOH intoxication in the presence of HS potentiates the physiological and metabolic alterations that may contribute to secondary brain injury.