Correlation of central venous-to-arterial carbon dioxide difference to arterial-central venous oxygen difference ratio to lactate clearance and prognosis in patients with septic shock

Abstract

Background: To assess the relationship between the ratio of difference of venoarterial CO 2 tension (P (v-a) CO 2 ) and difference of arterio-venous oxygen content (C (a-cv) O 2 ), i.e., ΔPCO 2 /ΔCaO 2 with lactate clearance (LC) at 8 and 24 h, to define a cutoff for the ratio to identify LC >10% and >20% at 8 and 24 h, respectively, and its association with prognosis in septic shock. Methods: Adult patients with septic shock were included in this prospective, observational cohort study. Blood samples for arterial lactate, arterial, and central venous oxygen and carbon dioxide were drawn simultaneously at time zero (T0), 8 h (T8), and 24 h (T24). At T8, patients were divided into Group 8A (LC ≥10%) and Group 8B (LC <10%). At T24, patients were divided into Group 24A (LC ≥20%) and Group 24B (LC <20%). Results: Ninty-eight patients were included. The area under the curve of ΔPCO 2 /ΔCaO 2 at T8 (0.596) and T24 (0.823) was the highest when compared to P(v-a) CO 2 and C(a-v) O 2 . The best cutoff of P(v-a) CO 2 /C (a-v) O 2 as predictor of LC >10% was 1.31 (sensitivity 70.6% and specificity 53.3%) and for LC >20% was 1.37 (sensitivity 100% and specificity 50%). At both T8 and T24, P(v-a) CO 2 /C (a-v) O 2 showed a significant negative correlation with LC. Groups 8A and 24A showed lower intensive care unit mortality than 8B and 24B, respectively. Values of P(v-a) CO 2 /C (a-v) O 2 at T8 were comparable, but at T24, there was a significant difference between the survivors and nonsurvivors ( P < 0.001). Conclusion: ΔPCO 2 /ΔCaO 2 predicts lactate clearance, and its 24 h value appears superior to the 8-h value in predicting LC and mortality in septic shock patients.

Venous Minus Arterial Carbon Dioxide Gradients in the Monitoring of Tissue Perfusion and Oxygenation: A Narrative Review

“…The combination of lactate and P cv-a CO 2 only resulted in trivial increases in the predictive value (AUROC = 0.930). In another recently published study in 98 patients with septic shock, P cv-a CO 2 /C a-cv O 2 at 24 h, but not at 8 h, was higher in nonsurvivors than in survivors and was a predictor of lactate clearance [ 96 ]. In contrast, lactate clearance was associated with outcomes at 8 h and 24 h.…”