Real-Time Measurements of Oral Mucosal Carbon Dioxide (P_OMCO₂) Reveals an Inverse Correlation With Blood Pressure in a Porcine Model of Coagulopathic Junctional Hemorrhage

Introduction: Shock states that occur during, for example, profound hemorrhage can cause global tissue hypoperfusion leading to organ failure. There is an unmet need for a reliable marker of tissue perfusion during hemorrhage that can be followed longitudinally. Herein, we investigated whether longitudinal P_OMCO₂ tracks changes in hemodynamics in a swine model of coagulopathic uncontrolled junctional hemorrhage. Materials and Methods: Female Yorkshire-crossbreed swine (n = 7, 68.1 ± 0.7 kg) were anesthetized and instrumented for continuous measurement of mean arterial pressure (MAP). Coagulopathy was induced by the exchange of 50 to 60% of blood volume with 6% Hetastarch over 30 minutes to target a hematocrit of <15%. A 4.5-mm arteriotomy was made in the right common femoral artery with 30 seconds of free bleeding. P_OMCO₂ was continuously measured from baseline through hemodilution, hemorrhage, and a subsequent 3-h intensive care unit period. Rotational thromboelastometry and blood gases were measured. Results: P_OMCO₂ and MAP showed no significant changes during the hemodilution phase of the experiment, which produced coagulopathy evidenced by prolonged clot formation times. However, P_OMCO₂ increased because of the uncontrolled hemorrhage by 11.3 ± 3.1 mmHg and was inversely correlated with the drop (17.9 ± 5.9 mmHg) in MAP (Y = −0.4122*X + 2.649, P = .02, r² = 0.686). In contrast, lactate did not significantly correlate with the changes in MAP (P = .35) or P_OMCO₂ (P = .37). Conclusions: Despite the logical appeal of measuring noninvasive tissue CO₂ measurement as a surrogate for gastrointestinal perfusion, prior studies have only reported snapshots of this readout. The present investigation shows real-time longitudinal measurement of P_OMCO₂ to confirm that MAP inversely correlates to P_OMCO₂ in the face of coagulopathy. The simplicity of measuring P_OMCO₂ in real time can provide an additional practical option for military or civilian medics to monitor trends in hypoperfusion during hemorrhagic shock.