Relationship of relevant factors to P(v-a)CO ₂/C(a-v)O ₂ ratio in critically ill patients

摘要

Objective This study investigated the factors related to the ratio of the venoarterial carbon dioxide tension difference [P(v-a)CO _(2)] to the arteriovenous oxygen content difference [C(a-v)O _(2)] (hereafter termed “Ratio”). Methods We retrospectively studied 1294 pairs of arterial and central venous blood gas measurements in 352 critically ill patients. A high Ratio was defined as?&?1.68 based on published literature. Measurements were divided into four groups: Group I [P(v-a)CO _(2) ?≤?6 mmHg/central venous oxygen saturation (ScvO _(2))?&?70%], Group II [P(v-a)CO _(2) ?≤?6 mmHg/ScvO _(2) ?≥?70%], Group III [P(v-a)CO _(2) ?&?6 mmHg/ScvO _(2) ?≥?70%], and Group IV [P(v-a)CO _(2) ?&?6 mmHg/ScvO _(2) ?&?70%]. Results The Ratio’s strongest correlation was with P(v-a)CO _(2) when compared with ScvO _(2) and hemoglobin in all data. The P(v-a)CO _(2) and ScvO _(2) were significantly higher and the hemoglobin and arterial oxygen saturation were significantly lower in the high Ratio measurements (&1.68) than low Ratio measurements (≤1.68). The P(v-a)CO _(2) was best for predicting a high Ratio. A P(v-a)CO _(2) threshold of 7 mmHg was associated with a sensitivity of 41.77% and specificity of 90.62% for predicting a high Ratio. Conclusions A high P(v-a)CO _(2) is the most relevant contributor to a high Ratio among all related factors in critically ill patients.