Diagnostic and predictive values of thirst, angiotensin II, and vasopressin during trauma resuscitation.

BACKGROUND Thirst perception involves neurochemical signals attributed to acute elevation of arginine vasopressin (AVP) and angiotensin II (AT2) levels, and may accompany acute hemorrhage. OBJECTIVE To determine whether thirst or plasma AVP or AT2 levels predict hemorrhagic shock, injury severity, or outcome in trauma patients at initial presentation. METHODS This was a prospective case series of adult subjects presenting as trauma activations to an urban level I trauma center. Subjects were included if they were alert and nonintoxicated. During resuscitation, subjects were queried for thirst perception using binary and continuous data formats employing a 100-mm nonhatched visual analog scale. Blood for AT2 and AVP assessment was obtained during initial laboratory collection. Other data were abstracted retrospectively from our trauma registry. Crude and stratified analyses (blunt and penetrating trauma) assessed the correlation of thirst, AVP, and AT2 to the initial shock index, base deficit, blood transfusion requirement, admission, and Injury Severity Score (ISS). Our institutional review board (IRB) granted a waiver of informed consent. RESULTS Of 105 subjects, the average age was 35 years (95% confidence interval [CI] 32 to 38), with 31% penetrating trauma. For AVP, there was no difference in thirst perception between subjects with normal (59 mm, 95% CI 47 to 71) versus elevated (63 mm, 95% CI 56 to 70) plasma levels. For AT2, results were likewise insignificant for normal (63 mm, 95% CI 56 to 70) versus elevated (58 mm, 95% CI 46 to 70) plasma levels. Thirst, AT2 level, and AVP level demonstrated no correlation to shock index, base deficit, transfusion requirement, hospital admission, or ISS. CONCLUSION The results of this study imply that thirst severity and AVP and AT2 plasma levels are not reliable predictors of impending hemorrhagic shock, injury severity, or outcome. The presence or absence of severe thirst should not be employed as a primary marker for dismissing or suspecting incipient shock.