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

Introduction

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.

Material and methods

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.

Results

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.

Conclusions

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.