Central venous-arterial carbon dioxide tension to arterial-central venous oxygen content ratio combined with lactate clearance rate as early resuscitation goals of septic shock

Abstract

Objective: To investigate the prognostic significance of central venous-arterial carbon dioxide tension to arterial-venous oxygen content ratio (Pcv-aCO(2)/Ca-cvO(2)) combined with lactate clearance rate (LCR) as early resuscitation goals of septic shock. Methods: One hundred and forty-five septic shock patients admitted to Second Department of Critical Care Medicine of Lanzhou University Second Hospital from March 2013 to May 2017 were enrolled in this study.All septic shock patients received an initial resuscitation therapy according to early goal-directed therapy.The arterial and central venous blood gases were measured simultaneously at baseline (T0) and 6 hours after resuscitation (T6). Pcv-aCO(2)/Ca-cvO(2) and LCR were calculated.Patients were classified into four groups according to Pcv-aCO(2)/Ca-cvO(2) and LCR at T6: group A, Pcv-aCO(2)/Ca-cvO(2)>1.8 and LCR<30%; group B, Pcv-aCO(2)/Ca-cvO(2)>1.8 and LCR≥30%; group C, Pcv-aCO(2)/Ca-cvO(2)≤1.8 and LCR<30%; group D, Pcv-aCO(2)/Ca-cvO(2)≤1.8 and LCR≥30%.General demographics, hemodynamic parameters, oxygen metabolism parameters, acute physiology and chronic health evaluation (APACHE Ⅱ) scores, sequential organ failure assessment (SOFA) scores, length of intensive care unit (ICU) stay, and 28-day mortality rate were compared among the 4 groups.A Kaplan-Meier curve showed the survival probabilities at day 28 using a log-rank test for multiple comparisons.Parameters were introduced into a Cox's proportional hazards regression model to analyze the prediction of 28-day mortality.Receiver operating characteristics (ROC) curves were constructed to evaluate the ability of Pcv-aCO(2)/Ca-cvO(2), LCR, Pcv-aCO(2)/Ca-cvO(2) combined with LCR at T6 to predict 28-day mortality. Results: Compared with patients in group A, patients from group D had the lower APACHE Ⅱ and SOFA score at day 3 (t=-2.909, -3.630, both P<0.05), shorter ICU stay (t=-2.575, P=0.011), and lower mortality rate at day 28 (χ(2)=3.124, P=0.011). Survival curves up to day 28, illustrated by Kaplan-Meier method, showed that group A had the shortest median survival time (χ(2)=10.332, P=0.016), difference between group A and group D was statistically significant (χ(2)=8.304, P=0.004). The Cox regression analysis revealed that Pcv-aCO(2)/Ca-cvO(2) (RR=3.888, 95%CI: 2.443-6.189, P<0.001) and LCR (RR=0.073, 95%CI: 0.008-0.640, P=0.018) at T6 were independent predictors of 28-day mortality.The area under ROC curve for Pcv-aCO(2)/Ca-cvO(2) combined with LCR (0.919, 95%CI: 0.862-0.958) was significantly greater than whether Pcv-aCO(2)/Ca-cvO(2) (0.862, 95%CI: 0.795-0.914) or LCR (0.820, 95%CI: 0.748-0.879) alone (Z=2.032, 2.364, both P<0.05). Conclusion: Combination of Pcv-aCO(2)/Ca-cvO(2) and LCR is better than single parameter to predict the risk of adverse outcomes of septic shock patients, and may provide useful information for assessing the adequacy of resuscitation at early stage of septic shock.