The Value Of Venous-Arterial Carbon Dioxide Partial Pressure Difference In Evaluating Volumetric Response And Tissue Perfusion In Patients With Septic Shock

Objective : To explore the value of central venous-arterial carbon dioxide partial pressure difference(Pcv-aCO2)in the evaluation of volume responsiveness,tissue perfusion,disease severity and prognosis of patients with septic shock.Methods : This is a single-center,prospective and clinical observational study.Patients with septic shock were admitted to Jiangsu Taizhou People’s Hospital in intensive care unit(ICU)from November 2019 to October 2020.All patients were treated according to the Early Bundle Treatment,and achieved the goal of recovery as soon as possible(MAP ≥ 65mmhg;CVP 8-12 mm Hg;urine volume ≥ 0.5ml/kg/h;Scv O2 ≥ 70%;lactate level was normal).Before the Early Bundle Treatment,6mm Hg was defined as the critical value of Pcv-aCO2 for grouping: High Pcv-aCO2 group(≥ 6mm Hg)and Low Pcv-aCO2 group(< 6mm Hg);After 6 hours of fluid resuscitation,the patients were divided into four subgroups according to the change trend of Pcv-aCO2:(1)H-L group:Pcv-aCO2 decreased(T0 ≥ 6 mm Hg,T6 < 6 mm Hg);(2)H-H group: Pcv-aCO2 continuously higher than normal(T0,T6 ≥ 6 mm Hg);(3)L-L group: Pcv-aCO2 continuously normal(T0,T6 < 6 mm Hg);(4)L-H group: Pcv-aCO2 increased(T0 < 6mm Hg,T6 ≥ 6 mm Hg).All patients were punctured right internal jugular vein(or right subclavian vein)indwelling central venous catheter.For the fluid shock test,500 ml of normal saline was infused from the central vein within 15 minutes.Cardiac output(CO)was measured by bedside echocardiography immediately before and after the fluid shock test.At the same time,blood samples from central vein and femoral artery were collected for blood gas analysis,and calculation of Pcv-aCO2.In order to further explore the predictive value of Pcv-aCO2 for volumetric reactivity,analysis the relationship between Pcv-aCO2 and CO is needed.The important physiological and laboratory indexes,blood gas of femoral artery and central vein were recorded immediately before fluid resuscitation(T0),3h after fluid resuscitation(T3)and 6h after fluid resuscitation(T6)for tissue perfusion assessment.By comparing the patients with vasoactive drugs,mechanical ventilation and blood purification treatment,28-day mortality,ICU length of stay and total length of stay and other indicators,and analyzing the relationship between Pcv-aCO2 and Acute Physiology and Chronic Health Evaluation II(APACHE II)and Sequential Organ Failure Assessment(SOFA),to explore the value of Pcv-aCO2 in evaluating the severity and prognosis of septic shock.Results : A total of 106 eligible patients with septic shock were enrolled in this study.There was no significant difference in general clinical data such as gender,age and infection site among the four groups(P > 0.05).1.In terms of volume responsiveness:Pcv-aCO2 was correlated with CO.When entering the group,the level of Pcv-aCO2 was different,and the volume responsiveness was different.Patients with high Pcva CO2 were more likely to show volume responsiveness after the fluid shock test,and the difference was statistically significant(P < 0.05).For these patients,Pcv-aCO2 had good predictive value for volume responsiveness,and the optimal critical value was 8.8mm Hg.2.In terms of tissue perfusion : There were significant differences in Scv O2,lactic acid and Pcv-aCO2 among the four groups before and after 6h of the Early Bundle Treatment(P < 0.05);There were correlations between Pcv-aCO2 and Scv O2 and lactic acid before and after the Early Bundle Treatment,and the correlation between Pcv-aCO2 and lactic acid was stronger(T0 : r = 0.800,P < 0.001;T6 : r =0.779,P < 0.001).3.In terms of the severity of the disease :Before the Early Bundle Treatment there were significant differences in APACHE II score and SOFA score among the groups(P < 0.01).And meanwhile,there was a positive correlation between Pcv-aCO2 and APACHE II score and SOFA score.After 6h of the Early Bundle Treatment,the change trend of Pcv-aCO2 was different,and the differences of vasoactive drugs,mechanical ventilation and blood purification treatment were also statistically significant(P < 0.05).4.In terms of prognosis : The change trend of Pcva CO2 was closely related to 28-day survival before and after the Early Bundle Treatment.Conclusion : 1.The baseline value of Pcv-aCO2 has a good correlation with CO.Patients with septic shock whose baseline Pcv-aCO2 ≥ 6mm Hg are more likely to show volume responsiveness after fluid shock test.For these patients,Pcv-aCO2 has a good predictive value for volume responsiveness.2.Pcv-aCO2 ≥ 6mm Hg indicates insufficient tissue perfusion.As a monitoring indicator,it can make up for the deficiency of using Scv O2 ≥ 70% as the end point of resuscitation.Combined with other monitoring indicators,it can better guide fluid therapy in patients with septic shock.3.Pcv-aCO2 is correlated with APACHE II score and SOFA score.Compared with APACHE II score and SOFA score,Pcv-aCO2 can judge the severity of the disease earlier,which can be used as one of the indicators to reflect the severity of the disease,and guide clinicians to intervene as soon as possible to improve the prognosis of patients.4.After the Early Bundle Treatment,the change trend of Pcv-aCO2 is different,and the prognosis of patients is significantly different.The patients whose Pcv-aCO2 was obviously decreased after treatment tend to have a better prognosis.