Buccal capnometry to guide management of massive blood loss

In both clinical and experimental settings, tissue P(CO2) measured in the oral mucosa is a practical and reliable measurement of the severity of hypoperfusion. We hypothesized that a threshold level of buccal tissue P(CO2) (P(CO2) BU)) would prognosticate the effects of volume repletion on survival. Twenty pentobarbital-anesthetized Sprague-Dawley male breeder rats, each weighing approximately 0.5 kg, were randomly assigned to one of four groups. Animals were bled over an interval of 30 min in amounts estimated to be 25, 30, 35, or 40% of total blood volume. One-half hour after the completion of bleeding, each animal received an infusion of Ringer lactate solution over the ensuing 30 min in amounts equivalent to two times the volume of blood loss. P(CO2) BU) was measured continuously with an optical P(CO2) sensor applied noninvasively to the mucosa of the left cheek. Arterial pressure and end-tidal CO2 were measured over the same interval. Neurological deficit and 72-h survival were recorded. Aortic pressures were restored to near baseline values for each of the four groups after fluid resuscitation. This contrasted with the improvement of P(CO2) BU), which differentiated between animals with short and long durations of postintervention survival. After electrolyte fluid resuscitation in rats subjected to rapid bleeding, noninvasive measurement of P(CO2) BU) was predictive of outcomes. Neither noninvasive end-tidal P(CO2) nor invasive aortic pressure measurements achieved such discrimination. Accordingly, P(CO2) BU) fulfills the criterion of a noninvasive and reliable measurement to guide fluid management of hemorrhagic shock.