| Background:Shock is present in approximately 1/3 of intensive care unit patients and is a common lethal factor in them.Among them,septic shock has a mortality rate of up to 50%.Lactate is a marker of altered tissue perfusion in critically ill patients and is one of the most important indicators of the status of circulatory shock.An early decrease in blood lactate levels may indicate improvement in systemic tissue hypoxia and is associated with a decrease in the mortality rate.The results of several studies suggest that lactate clearance has a good predictive value of mortality in various circulatory shocks.Microcirculatory dysfunction is the most fundamental pathophysiological alteration in shock,and changes in microcirculation occur prior to systemic hemodynamic deterioration.Decreases in tissue oxygen saturation(StO2)monitored by Near-infrared spectroscopy are a reliable marker of severe tissue hypoperfusion,and changes in StO2 may help detect the development or worsening of tissue hypoperfusion,for which predictive value exists.The masseter,deltoid,thenar and knee are four common sites used for StO2 monitoring,which can reflect the microcirculation of different parts of the body in patients in shock.During passive leg raising(PLR),tissue oxygen saturation at different sites experienced both changes in systemic and local blood flow,reflecting systemic microcirculatory reactivity and improving the predictive value of tissue oxygen saturation.Method:A prospective study was used to include shock patients who met the inclusion criteria admitted to the medical intensive care unit of Peking Union Medical College Hospital from April 2021 to February 2022.StO2 was obtained from 4 sites,including the masseter,deltoid,thenar and knee,within 48 hours of admission.Moreover,weighted StO2 representing systemic microcirculation was generated for analysis based on the percentage of body surface area.There were 2 cohorts as follows:(1)Patients in shock with combined lactate≥3 mmol/L(n=34).Static StO2 was monitored.Patients were divided by lactate clearance into a lactate clearance group(n=19)and a lactate nonclearance group(n=15).Patients were assessed for the diagnostic value of static StO2 to determine lactate clearance in patients with shock combined with hyperlactatemia.(2)Patients in shock who underwent passive leg raising(n=29).Hemodynamic and multisite dynamic StO2 were continuously monitored during PLR,and cardiac output were monitored before and after PLR.Patients were divided into survival(n=18)and nonsurvival(n=11)groups according to 14-day mortality;and into fluid responsiveness(n=10)and no fluid responsiveness(n=19)groups according to fluid responsiveness(defined as 10%increase or more of CO during PLR).The diagnostic value of dynamic StO2 during PLR to determine 14-day mortality and fluid responsiveness was assessed in patients with shock.The area under the receiver operating characteristic(AUROC)was used to assess the predictive value of static StO2 and dynamic StO2.Result:(1)Static tissue oxygen saturation and lactate clearance.Baseline deltoid,knee and weighted tissue oxygen saturation were all positively correlated with lactate clearance(deltoid R=0.42,P=0.013;knee R=0.64,P<0.001;weighted R=0.62,P<0.001).Except for the masseter,baseline deltoid,thenar,knee,and weighted StO2 all predicted 6 hour-lactate clearance in patients with shock.Among them,weighted StO2 predicted a maximum area under the curve of 0.92(0.82-1.00)for lactate clearance,followed by knee 0.87(0.73-1.00).(2)Dynamic tissue oxygen saturation after PLR and 14-day mortality.Significant negative correlations were observed between dynamic masseter StO2 after PLR and baseline lactate,as well as 6-hour lactate(baseline lactate R=-0.39,P=0.036;6-hour lactate R=-0.45,P=0.014),reflecting 6-hour perfusion status in patients with shock.Furthermore,dynamic masseter StO2 after PLR predicted 14-day mortality with an AUROC of 0.77(0.59-0.94).(3)Dynamic tissue oxygen saturation and fluid responsiveness after PLR.Positive correlation was existed between dynamic deltoid StO2 and change in cardiac output(CO)during PLR(R=0.44,P=0.018).Both dynamic deltoid StO2 and knee StO2 predicted fluid responsiveness in patients with shock,with AUROC of 0.78(0.6-0.97)and 0.75(0.53-0.98).Moreover,the diagnostic accuracy of dynamic tissue oxygen saturation of the deltoid and knee for fluid responsiveness was robust in patients with septic shock,in patients without mechanical ventilation,and when fluid responsiveness was defined as a change of CO more than 10%during volume expansion.Conclusion:In patients with shock and hyperlactatemia,static weighted StO2 monitored by NIRS can be used to predict 6-hour lactate clearance,and combined with dynamic masseter StO2 after PLR can better assess the patient’s perfusion status and improve the diagnostic accuracy of 14-day mortality.Meanwhile,dynamic deltoid and knee StO2 after PLR can be used to determine the fluid responsiveness of patients with shock,guiding subsequent treatment plans. |
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