Afterload-Related Cardiac Performance Is Associated With Severity Of Septic Shock:A Cohort Study

Background:The prognosis of septic shock combined with septic cardiomyopathy(SCM)is poor.At present,there are few study on the application of afterload-related cardiac performance in the diagnosis of SCM and the assessment of the severity of septic shock at home and abroad.Objective:The study is aimed to explore the relationship between afterload-related cardiac performance(ACP)and the severity of septic shock in the early stage in Chinese population.Method:A retrospective cohort analysis was conducted among 69 patients with septic shock who were admitted to the intensive care unit in Zhujiang Hospital of Southern Medical University and Bao’an Hospital of Southern Medical University.All patients were monitored with Pulse-induced Contour Cardiac Output(PiCCO)system for invasive hemodynamics monitoring.Cardiac index(Cl),mean arterial pressure(MAP),central venous pressure(CVP)and systemic vascular resistance index(SVRI)were recorded 72 hours after admitted.The systemic vascular resistance(SVR)was calculated according to the formula SVR= 80×(MAP-CVP)/CO.The normal predicted value of CO under the corresponding SVR was calculated by the formula COpredict=560.68×SVR-0.64.The ratio of CO moasure to CO prediction was ACP.The lowest value of ACP within 72 hours after the admitted was recorded,and SCM was diagnosed with ACP≤0.8.Meanwhile,we calculate the cardiac power output(CPO)and cardiac power index(CPI)and record it’s lowest values.We also record the lowest values of CO,CI,SVR and SVRI within 72 hours and their change rates(ΔCO,ΔCI,△SVR,△SVRI),as well as the demographic characteristic of the patients,organ function related indicators(lowest values of platelet,hemoglobin,oxygenation index within 72 hours,and the highest values of serum creatinine,urea nitrogen,arterial lactie acid,cTnl,NT-proBNP),fluid balance,norepinephrine demand and prognostic information.Result:Using 0.8 as a cut-off point,as many as 76.8%of the patients could be diagnosed as SCM in the early stage of septic shock.After regression analysis of several related factors,it was found that ACP was independently related to the level of arterial lactic acid[β=-20.02,95%Cl(-32.71,-7.34),p<0.01].Comparing the patients with normal cardiac function,patients with SCM were elder(54.88±11.13 vs.62.26 ±15.76,P<0.05);and their demand for norepinephrine was higher at admission(0.83±0.58 μg/kg/min vs.0.75±1.05μg/kg/min,p<0.05),24h(1.05±1.13μg/kg/min vs.0.56 ±0.66 μg/kg/min,p<0.05)and 48h(0.65±0.57μg/kg/min vs.0.38±0.64 μg/kg/min,p<0.05).Compared with the norepinephrine demand at admission,there was no significant difference in the trend of norepinephrine demand at different time points between patients with SCM and those with normal cardiac function.The fluid balance of patients with SCM in 24 to 48 hours was significantly lower than that of patients with normal cardiac function(-389±1154 ml vs.461±1194.05 ml,p<0.05),but there was no significant difference at other time points.Compared with the fluid balance at the first 24 hours after admission,there was no significant difference in fluid balance between patients with SCM and those with normal cardiac function between 24h and 48h,48h and 72h.ACP is positively correlated with CPO(r= 0.836)and CPI(r= 0.802)and has a good correlation.Conclusion:Taking ACP≤0.8 as the diagnostic cut-off point,we found that SCM was quite common in the early stage of septic shock,it may also affect the patient’s fluid balance and norepinephrine demand.The level of ACP was negatively correlated with the level of arterial lactic acid independly.ACP may be a good parameter reflecting the severity of septic shock.Consistency to the old parameters reflecting the cardiac power output,ACP may be a useful tool to evaluate the cardiac function of SCM.