Accuracy Of The P（cv-a）CO₂ In Diagnosis Of Low Cardiac Output Of Sepsis

BackgroundThere is a certain correlation between the central venous-arterial carbon dioxide difference(P(cv-a)CO2)and cardiac output in patients with sepsis,which has the value of evaluating cardiac output at the bedside.However,the correlation between central venous-arterial carbon dioxide difference and cardiac output is highly variable.In order to evaluate the accuracy and reliability of this method,we will study the accuracy with diagnostic testObjectiveThe aims of this study was to evaluate the accuracy of central venous-arterial blood carbon dioxide difference in the diagnosis of low cardiac output in patients with sepsis and to verify its relevance.MethodsWe conducted a retrospective case selection of patients.These patients were placed with a femoral PiCCO catheter and a central venous catheter after admission.Venous and arterial blood gas samples were collected from the central venous catheter and the femoral arterial catheter at the same time and analyzed to obtain the central venous-arterial blood carbon dioxide difference.At the same time,the mean value of three consecutive hemodynamic parameters was obtained by the thermal dilution technique,and the low cardiac output was defined as a cardiac index(CI)<2.5L/min/m2.The accuracy of central venous-arterial blood carbon dioxide difference was evaluated by the area under the curve(AUC)of the receiver operating characteristic curve(ROC)in patients with sepsis.ResultsWe screened 82 patients with sepsis,and finally included 29 patients(22males and 7females),and obtained 105 person-times venous and arterial blood gas analysis results and hemodynamic parameters.When P(cv-a)CO2≥6.75mmHg can detect the low cardiac output status of patients with sepsis,it is used to detect the cardiac index<2.5L/min/m2.The sensitivity of this threshold is 72.2%and the specificity is 75.9%.The AUC is 0.791(95%CI:0.673-0.908),the positive predictive value is 38.20,and the negative predictive value is 93.0%.The accuracy of ScvO2,and P(cv-a)CO2was evaluated by ROC curves.The AUC of ScvO2was 0.712(95%Cl:0.598-0.825),that is no significant difference compared to P(cv-a)CO2(P=0.264).In addition,P(cv-a)CO2 has no diagnostic value when detecting high cardiac output(CI>4.5L/min/m2),and the AUC is 0.524(95%CI:0.362-0.687).According to the adjustment of covariates,the AUC of P(cv-a)CO2 for detecting low cardiac output in sepsis showed robustness before and after adjusting CRRT factors.There is a negative correlation between the cardiac index and P(cv-a)CO2(R=-0.40,P<0.001).when the cardiac index<2.53L/min/m2,it shows a negative linear correlation significantly between the cardiac index and P(cv-a)CO2.The regression coefficient is-3.43(95%CI:-5.58,-1.28;P=0.002).ConclusionWhen CI<2.53L/min/m2,P(cv-a)CO2 showed a significant linear correlation with cardiac output.P(cv-a)CO2≤6.75mmHg can generally exclude low cardiac output in patients with sepsis.