Abstract 370: Oral-Mucosal PCO 2 During Hemorrhagic Shock Closely Monitors Its Time Course, Severity, and Reversal Outperforming Blood Lactate Measurement

Abstract

Objective: Oral-Mucosal PCO 2 (P OM CO 2 ) has been shown to closely correlate with the splanchnic mucosal PCO 2 and provide information on its microcirculation. We used a swine model of controlled hemorrhagic shock to assess the potential clinical relevance of monitoring P OM CO 2 to assess its clinical course, severity, and treatment effect. Methods: The study was performed on six male domestic pigs (37.9±1.4 kg). P OM CO 2 was measured using a non-invasive disposable sensor clipped to the cheek, developed by ExoStat Medical. Blood was removed over 120 minutes from the right atrium using a LabVIEW-controlled pump according to a mono-exponential decay curve modeling spontaneous bleeding and reinfused in 20 minutes observing the animal for a total of 180 minutes. Results: A total of 1,491±193 ml corresponding to 65.5% of the estimated blood volume were removed inducing the characteristic hemodynamic features of hemorrhagic shock including tachycardia, hypotension, reduced cardiac output, and reduced systemic oxygen delivery with increased systemic oxygen extraction. P OM CO 2 closely paralleled the time course of blood removal showing an early and steady increase from 85±5 mmHg at baseline to 144±32 mmHg after 120 minutes. Blood reinfusion rapidly reduced the P OM CO 2 to 130±17 mmHg after 20 minutes and 96±14 mmHg at the end of 180 minutes, coincident with reversal of hemorrhagic shock. P OM CO 2 also closely tracked changes in systemic oxygen extraction. Concurrent measurements of blood lactate demonstrated a slower increase during the hemorrhagic shock period (from 1.1±0.3 to 3.0±0.3 mmol/l) with further increase (not decrease) to 5.4±2.0 mmol/l after blood reinfusion, remaining at 4.3±0.8 mmol/l by the end of the 180-minute observation period. Conclusions: The study demonstrated capability of P OM CO 2 to closely and non-invasively track hemodynamic and metabolic changes occurring during hemorrhagic shock. P OM CO 2 outperformed blood lactate which exhibited a slower and delayed response. Thus, P OM CO 2 may provide a clinically practical and non-invasive means to monitor hemorrhagic shock assessing its severity, clinical course, and treatment effect.