Buccal partial pressure of carbon dioxide outweighs traditional vital signs in predicting the severity of hemorrhagic shock in a rat model

Background

Hemorrhagic shock (HS) is a leading cause of death in both military and civilian settings. Researchers have investigated different parameters as predictors of HS, but reached inconsistent conclusions. We hypothesized that buccal partial pressure of carbon dioxide (PCO₂) was a better predictor of HS than traditional vital signs.

Materials and methods

Twenty-four anesthetized Wistar rats were randomly divided into four groups: one control group (no bleeding) and three surgical groups (25%, 35%, and 45% blood loss). Hemorrhage was induced by withdrawing blood from the left femoral artery over a period of 30 min. After that, resuscitation was performed on animals in surgical groups using the Ringer lactate solution. Buccal PCO₂ was continuously measured by a newly designed sensor holder during the experiments. Traditional vital signs, cardiac output, base excess, and microvascular perfusion (MPF) were also measured or calculated.

Results

Buccal PCO₂ differed significantly among four groups beginning at 20 min, approximately 10 min earlier than the shock index and more earlier than the heart rate, systolic blood pressure, and mean arterial pressure. Buccal PCO₂ correlated well with cardiac index and the changes in MPF. The correlation coefficients with cardiac index, chest MPF, and upper-limb MPF for buccal PCO₂ were 0.781, −0.879, and −0.946, respectively. Besides, buccal PCO₂ showed a good value for predicting mortality. Furthermore, an approximate critical threshold of buccal PCO₂ was also identified for predicting the severity of HS.

Conclusions

Buccal PCO₂ was a noninvasive, sensitive indicator of HS than traditional vital signs and may help on-scene rescuers administer early treatment of injured patients.