Hemodynamic effects of different fluid volumes for a fluid challenge in septic shock patients

Background:It is still unclear what the minimal infusion volume is to effectively predict fluid responsiveness.This study was designed to explore the minimal infusion volume to effectively predict fluid responsiveness in septic shock patients.Hemodynamic effects of fluid administration on arterial load were observed and added values of effective arterial elastance(Ea)in fluid resuscitation were assessed.Methods:Intensive care unit septic shock patients with indwelling pulmonary artery catheter(PAC)received five sequential intravenous boluses of 100 mL 4%gelatin.Cardiac output(CO)was measured with PAC before and after each bolus.Fluid responsiveness was defined as an increase in CO>10%after 500 mL fluid infusion.Results:Forty-seven patients were included and 35(74.5%)patients were fluid responders.CO increasing>5.2%after a 200 mL fluid challenge(FC)provided an improved detection of fluid responsiveness,with a specificity of 80.0%and a sensitivity of 91.7%.The area under the ROC curve(AUC)was 0.93(95%CI:0.84-1.00,P<0.001).Fluid administration induced a decrease in Ea from 2.23(1.46-2.78)mmHg/mL to 1.83(1.34-2.44)mmHg/mL(P=0.002),especially for fluid responders in whom arterial pressure did not increase.Notably,the baseline Ea was able to detect the fluid responsiveness with an AUC of 0.74(95%CI:0.59-0.86,P<0.001),whereas Ea failed to predict the pressure response to FC with an AUC of 0.50(95%CI:0.33-0.67,P=0.086).Conclusion:In septic shock patients,a minimal volume of 200 mL 4%gelatin could reliably detect fluid responders.Fluid administration reduced Ea even when CO increased.The loss of arterial load might be the reason for patients who increased their CO without pressure responsiveness.Moreover,a high level of Ea before FC was able to predict fluid responsiveness rather than to detect the pressure responsiveness.

Monitoring Changes in Hepatic Venous Velocities Flow after a Fluid Challenge Can Identify Shock Patients Who Lack Fluid Responsiveness

Background： Evaluating the hemodynamic status and predicting fluid responsiveness are important in critical ultrasound assessment of shock patients. Transthoracic echocardiography with noninvasive diagnostic parameters allows the assessment of volume responsiveness. This study aimed to assess tile hemodynamic changes in the liver and systemic hemodynamic changes during fluid challenge and during passive leg raising （PLR） by measuring hepatic venous flow （HVF） velocity. Methods： This is an open-label study in a tertiary teaching hospital. Shock patients with hypoperfusion who required fluid challenge were selected for the study. Patients 〈l 8 years old and those with contraindications to PLR were excluded from the study. Baseline values were measured, PLR tests were performed, and 500 ml of saline was infused over 30 rain. Parameters associated with cardiac output （CO） in the left ventricular outflow tract were measured using the Doppler method. In addition, HVF velocity and right ventricular function parameters were determined. Results： Middle hepatic venous （MHV） S-wave velocity was positively correlated in all patients with CO at baseline （r= 0.706, P〈 0.01 ） and after volume expansion （r= 0.524, P = 0.003）. CO was also significantly correlated with MHV S-wave velocity in responders （r = 0.608, P 〈 0.01）. During PLR, however, hepatic venous S-wave velocity did not correlate with CO. For the parameter AMHV D （increase in change in MHV D-wave velocity after volume expansion）, defined as （MHV D - MHV Dtaseline）/MHV DBaseli.,e x 100%, 〉21% indicated no fluid responsiveness, with a sensitivity of 100%, a specificity of 71.2%, and an area under the receiver operating characteristic curve of 0.918. Conclusions： During fluid expansion, hepatic venous S-wave velocity can be used to monitor CO, whether or not it is increasing. AMHV D 〉21% indicated a lack of fluid responsiveness, thus helping to decide when to stop infusions.

Passive Leg Raising in Intensive Care Medicine

Fluid challenge is a common diagnostic method to help the physician detennine fluid responsiveness, which is an important component of fluid management in critically ill patients）H Raising legs of a patient induces the transfer of a variable amount of blood （approximately 200-300 ml） contained in the venous reservoir from the limb to central venous compartment. According to Franck-Starling curve, this transient increase of preload might lead to an increase in cardiac output （CO） in thture responders resulting from their preload-reserve status. Many clinical studies have validated passive leg raising （PLR）, and the advantage of PLR is attractive in Intensive Care Unit （ICU）. Recently, PER has been suggested as a simple and potential method to predict fluid responsiveness, which is similar to an ＂auto-fluid challenge＂ without a drop of fluid. However, one study revealed poor application of PLR in the real world, We acknowledged that the lack of education on PLR would result in the current practice. On the other hand, the application of PLR might be not simple in clinical practice, and the holy grail of fluid responsiveness still needs to be discovered. The standard of PLR has not been established, and some questions of PLR merit discussion.