Buccal capnometry for quantitating the severity of hemorrhagic shock

We have recently demonstrated that measurement of buccal mucosal PCO2 (PBUCO2) is a reliable alternative to sublingual mucosal PCO2 for measuring the severity of hemorrhagic shock. We hypothesized that measurement of PBUCO2 would serve as a continuous and a more sensitive and specific measurement for predicting survival during hemorrhagic shock than conventional measurements and thereby better guide initial management. Four groups of five pentobarbital anesthetized Sprague-Dawley rats were randomly assigned to be bled over 30 min in amounts estimated to be 25%, 30%, 35%, or 40% of total blood volume. With an optical PCO2 sensor applied noninvasively to the mucosa of the left inner cheek, PBUCO2 was continuously measured together with arterial pressure, end-tidal PCO2, and intermittent measurement of cardiac output, arterial blood lactate, and base deficit. Surviving animals had free access to water and food but no other treatment during the 72-h interval after recovery from anesthesia. After an estimated 40% blood loss, all animals died within 1 h. In the remaining animals, arterial pressure, end-tidal carbon dioxide, cardiac index, blood lactate, and base deficit each failed to discriminate among animals with 35%, 30%, and 25% acute blood losses. This contrasted with PBUCO2, which discriminated between the magnitude of massive blood loss and untreated survival. Buccal mucosal PCO2 was predictive of outcome after rapid bleeding when compared with arterial pressure, end-tidal carbon dioxide, cardiac index, arterial blood lactate, and base deficit. This measurement is therefore likely to serve as a useful guide for the immediate management of hemorrhagic shock.