The Study Of Fluid Responsiveness Predicted By Application Of Positive End-expiratory Pressure In Patients With Septic Shock

Background:Fluid resuscitation is an important part of treatment of patients with severe septic and septic shock.In the clinical setting, the assessment of preload and determination of whether the patient is fluid responsive is very important,but may be difficult. Several reports have shown that central venous pressure (CVP) and pulmonary artery wedge pressure (PAWP) are poor indicators of preload or fluid responsiveness in critically ill patients because of heart rate,compliance,valve function,pulmonary vein pressure,the pressure in chest and any other factors.In recent years,dynamic indicators,such as strock volume variation(SVV) and pulse pressure variation (PPV), have been shown to be superior indicators of fluid responsiveness compared to static measurements,but these indicators require specific monitoring equipments and may be unreliable in clinical practice because of arrhythmias, spontaneous breathing efforts or other feasibility problems,the applications are greatly limited.So the study of some non-invasive,simple and accurate volume indicators become very meaningful.In this research,we study changes in haemodynamic parameters induced by elevation of positive end-expiratory pressure(PEEP) to assess fluid responsiveness of patients with septic shock.Objective:We study a new method for evaluation of fluid responsiveness of patients with septic shock through the research of changes in haemodynamic parameters induced by elevation of positive end-expiratory pressure(PEEP) in 30 cases of mechanical ventilation patients with septic shock.Methods:We conducted a prospective study of 30 cases of patients with septic shock in intensive care unit (ICU).Through setting PEEP from 5cmH2O to 15cmH2O,we recorded the changes in haemodynamic parameters induced by elevation of positive end-expiratory pressure(PEEP) during an end-expiratory pause,including heart rate(HR),mean arterial pressure(MAP), systolic arterial pressure(SAP),central venous pressure(CVP),then calculated △MAP and ASAP.At the same time,we measured and recorded the changes in stroke volume index(SVI),cardiac index(CI), strock volume variation(SVV),pulse pressure variation(PPV),intrathoracic blood volume index(ITBVI),systemic vascular resistance index(SVRI) by using the method of thermodilution and pulse contour analysis.And then reset PEEP to 5cmH2O for 5 minutes,We conducted the fluid challenge by giving 500ml 0.9% physiological saline within 30 minutes,then calculated ACI, fluid responsiveness was defined as an increase of cardiac index (CI) of 10%.The receiver operating characteristic curves (ROC) was drawn to evaluate the value of △MAP、△SAP、SVVPPV in predicting fluid responsiveness.Result:In the responsers,during elevation of PEEP from 5cmH2O to 15cmH2O, MAP, SAP, CI, SVI, SVRI, ITBVI decreased (all P<0.05),meanwhile SVV,PPV,CVP increased (all P<0.05),but there was no change in HR(P>0.05).In the non-responsers,there were no change in MAP,SAP, HR(all P>0.05), butCI,SVI,ITBVI decreased (all P<0.05),meanwhile SVV,PPV,CVP,SVRI increased (all P<0.05).At PEEP of 5cmH2O,there were no significant difference in CVP between responsers and non-responsers,but ITBVI was lower in responsers than non-responsers(P<0.05), SVV, PPV were higher significantly in responsers than non-responsers(all P<0.01).The receiver operating characteristic curves (ROC) was drawn to evaluate the value of AMAP, ASAP, SVV, PPV in predicting fluid responsiveness, with AUC 0.837、0.768、 0.855.0.855 respectively,the AUC 95% confidence intervals for △MAP was 0.686～0.988.The best cut-off value for AMAP predicting fluid responsiveness was-13.5%,with a sensitivity of 81.3%,a specificity of 85.9%.Conclusions:MAP decrease induced by elevation of PEEP can predict fluid responsiveness in patients with septic shock, it is simple,feasible, non-invasive and accurate.