The Predictive Ability of PV-ACO2 Gap and PV-ACO2/CA-VO2 Ratio in Shock: A Prospective, Cohort Study.

Introduction: Compromised tissue oxygenation leads to anaerobiosis, leading to organ failure and death. This study attempts to demonstrate the predictive abilities of the Pv-aCO2 gap and Pv-aCO2/Ca-vO2 ratio in shock patients undergoing resuscitation.

Methods: In a prospective study, consecutive patients with shock were included. Timed measurements of Pv-aCO2 gap, ScvO2, lactate, and Pv-aCO2/ Ca-vO2 ratio were obtained. The association between the mortality and each variable at all intervals was analyzed. Receiver operating characteristics curves were built.

Results: Fifty patients were enrolled. Intensive care unit survivors had a higher Pv-aCO2/ Ca-vO2 ratio at time 0 (0.21, interquartile range [IQR] 0.14 vs. 0.27, IQR 0.38, P = 0.032) and at 3 h (0.27, IQR 0.08 vs. 0.21, IQR 0.12, P = 0.035).Twenty-eight day survival was higher in patients with a low Pv-aCO2 gap at time 0 (7.5, IQR 7 vs. 4.8, IQR 5, P = 0.007).Baseline Pv-aCO2 gap and Pv-aCO2/Ca-vO2 ratio showed good ability to predict 28-day mortality as seen by AUC 0.728 (95% CI 0.578-0.877, P = 0.007) and 0.711 (95% CI 0.563-0.860, P = 0.013). A cut-off point of Pv-aCO2 gap ≥6 mm Hg identified 28-day mortality (75% vs. 45.5%, P = 0.034). The best cutoff values, at baseline, to predict 28-day mortality were 0.25 for the Pv-aCO2/Ca-vO2 ratio (sensitivity 58%, specificity 85%, LR+ 3.86, LR- 0.49) and 6.3 for the Pv-aCO2 gap (sensitivity 58%, specificity 79%, LR+ 2.76, LR- 0.53).

Conclusion: This study suggests that Pv-aCO2 gap and Pv-aCO2/Ca-vO2 ratio are discriminating predictors of 28-day mortality and can be used to provide supplementary information during resuscitation in shock.