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 POMCO2 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. POMCO2 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: POMCO2 and MAP showed no significant changes during the hemodilution phase of the experiment, which produced coagulopathy evidenced by prolonged clot formation times. However, POMCO2 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, r(2) = 0.686). In contrast, lactate did not significantly correlate with the changes in MAP (P = .35) or POMCO2 (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 POMCO2 to confirm that MAP inversely correlates to POMCO2 in the face of coagulopathy. The simplicity of measuring POMCO2 in real time can provide an additional practical option for military or civilian medics to monitor trends in hypoperfusion during hemorrhagic shock.