Relative bradycardia in patients with isolated penetrating abdominal trauma and isolated extremity trauma.

A relative bradycardia is sometimes seen in patients with hemorrhagic shock. The phenomenon of relative bradycardia in civilian patients with isolated penetrating abdominal trauma and isolated severe extremity trauma who presented to an urban trauma center was studied retrospectively. Relative bradycardia was defined as a pulse rate of less than 100 with a concomitant systolic blood pressure of less than 100 mm Hg. There were 256 patients with isolated penetrating abdominal trauma and 938 patients with isolated severe extremity trauma. The incidence of relative bradycardia was 3.1% (eight of 256) in the group with abdominal trauma and 1.8% (17 of 938) in the group with extremity trauma. A pulse rate less than 100 was documented in 35.2% of all patients presenting with a systolic blood pressure less than 100 mm Hg (25 of 71). A pulse rate of less than 100 was documented in 45.8% of all patients presenting with a systolic blood pressure less than 90 mm Hg (11 of 24). No increased mortality was seen in the patients who evidenced relative bradycardia. The effect of intraperitoneal bleeding on the normal tachycardic response to hemorrhage also was studied. After controlling for volume status using various operational definitions of shock, no statistically significant (P less than .01) difference in pulse rates was noted between patients with isolated penetrating abdominal trauma and isolated extremity trauma. This result suggests that the previously theorized vagal-mediated bradycardia unique to intraperitoneal bleeding may not exist.