THE EFFECT OF COCAINE ON THE PHYSIOLOGICAL-RESPONSE TO HEMORRHAGIC-SHOCK

Background. Bradycardia is thought to be an uncommon and abnormal resp onse to acute blood loss. A review of trauma patients (n = 84) admitte d during a 1-year period with a systolic blood pressure of less than 1 00 mm Hg revealed that 45% had relative bradycardia (heart rate < 100 beats/minute). Cocaine use was recorded more often in this group (76% versus 26%; p < 0.05) compared with patients with tachycardia (heart r ate greater-than-or-equal-to 100 beats/minute). We investigated the ef fect of cocaine use on the response to acute blood loss in an animal m odel of hemorrhagic shock. Methods. Rats were given intraperitoneal co caine 20 mg/kg/day for 14 days (n = 10) or saline solution (n = 10). T he rats were bled until 30% of their blood volume was shed; they were resuscitated 30 minutes later. Results. Cocaine-treated rats showed a decreased 24-hour survival rate (50% versus 100%; p < 0.05), a relativ e bradycardic response compared to baseline heart rate (-8.9% +/- 6.4% versus 7.5% +/- 3.5%; p < 0.05), and a greater drop in mean arterial blood pressure (-55.5% +/- 4.8% versus -37.0% +/- 5.5%; p < 0.05) by 5 minutes of shock. Cocaine-treated rats were more acidotic after shock compared to controls (pH 7.36 +/- 0.03 versus 7.44 +/- 0.02; p < 0.05 ). Conclusions. Cocaine had a deleterious effect on experimental hemor rhage. The bradycardic response observed in our trauma patients may be due, in part, to cocaine abuse, and we postulate that chronic cocaine use alters the normal adrenergic response to blood loss. (SURGERY 199 3;114:429-35.)