Oral-Mucosal PCO₂ during hemorrhagic shock closely Monitors its time Course, Severity, and reversal outperforming...

Given the redistribution of blood flow away from non-immediately vital territories during hemorrhagic shock, we investigate whether monitoring the oral mucosal PCO₂ (P_OMCO₂) as a surrogate of splanchnic circulation, could closely recognize the onset, assess severity, and identify reversal of hemorrhagic shock.

The study was performed on six male pigs (38.4 ± 1.6 kg). P_OMCO₂ was measured using a non-invasive sensor clipped to the cheek. Blood was removed over 120 min from the right atrium modeling spontaneous bleeding and reinfused in 20 min observing the animal for 180 min.

A total of 1485 ± 188 ml (i.e., 64.6 ± 9.5 % of the estimated blood volume) was removed inducing severe hemorrhagic shock. P_OMCO₂ closely paralleled the blood volume change (R² = 0.59, p < 0.001) showing an early and steady increase from 86 ± 5 mmHg at baseline to 152 ± 28 mmHg after 120 min. Blood reinfusion reduced the P_OMCO₂ to 138 ± 37 mmHg after 15 min and 97 ± 34 mmHg at the end of 180 min, coincident with the reversal of hemorrhagic shock. Blood lactate less accurately paralleled the blood volume change (R² = 0.14, p < 0.001) showing a slower increase during hemorrhagic shock (from 1.1 ± 0.3 to 4.2 ± 1.8 mmol/l after 120 min) with further increase to 5.2 ± 1.7 mmol/l following blood reinfusion at minute 150 min, remaining at 4.0 ± 1.5 mmol/l by the end of the 180-minute observation period.

P_OMCO₂ monitoring may provide a clinically practical non-invasive indicator of hemorrhagic shock assessing its severity, clinical course, and treatment effect outperforming blood lactate which exhibited a slower and delayed response.