| BackgroundWith the social development of aging population,the number of elderly patients is increasing.Due to the degradation of their vital organs function and the decline of cardiopulmonary reserve function,the operative mortality is further increasing.Intraoperative fluid therapy is an important measure to maintain normal organ function,tissue perfusion and hemodynamic stability.In elderly patients,due to increased vascular fragility,decreased left ventricular compliance,impaired cardiac reserve function,disturbed fluid balance and other reasons,hypervolemia can easily lead to an increase in hydrostatic pressure,which can lead to undesirable consequences such as tissue edema,heart dysfunction and even acute pulmonary edema,while hypovolemia can lead to hypotension,inadequate tissue perfusion and even organ failure.Therefore,fluid therapy of elderly patients is one of the key and difficult points in perioperative period.Goal-directed Fluid Therapy(GDFT)is through continuous and accurate hemodynamic monitoring to obtain the corresponding target parameters,which can judge the volume state and fluid responsiveness of patients in real time,so as to optimize cardiac output,ensure perfusion and oxygen supply of organs and tissues,implement individualized fluid therapy strategy,thereby reduce unreasonable volume therapy.At present,GDFT mostly chooses functional hemodynamic parameters such as stroke volume variation(SVV)and pulse pressure variation(PPV)to determine the patient's response to fluid challenge.Due to the use of lung protective ventilation strategy such as low tidal volume intraoperative,it is worth exploring whether SVV and PPV can accurately predict fluid responsiveness.At the same time,the thoracic and pulmonary compliance of elderly patients decreased,and the accuracy of functional hemodynamic parameters may be further affected by factors such as limited thoracic movement and increased intrathoracic pressure in prone position.It has been found that mini-fluid challenge test can be used to predict the fluid responsiveness of adult patients during surgery,but its effectiveness in elderly patients is not clear,and few studies have been done in prone position surgery.Therefore,the purpose of this research was to explore the feasibility of mini-fluid challenge test in predicting fluid responsiveness of elderly patients in prone position under general anesthesia.Material and MethodA total of 48 elderly patients with ASA grade ?-? who underwent spinal surgery in prone position from June 2019 to December 2019 were enrolled.Under local anesthesia,a radial arterial catheter was inserted and connected to FloTrac/Vigileo system to obtain hemodynamic parameters.Patients were infused with 5 ml/kg lactate Ringer's solution in prone position under general anesthesia for 10 min to observe the fluid responsiveness.Patients were mechanically ventilated using a volume-control mode with a tidal volume of 6 ml/kg of ideal body weight during the operation.The hemodynamic parameters were observed and recorded in supine position before changing posture(T1),prone position after changing posture 5 min(T2),1 min after infusion of 1 ml/kg fluid(T3),1 min after infusion of 1 ml/kg fluid(T4),1 min after infusion of 3 ml/kg fluid(T5).Including systolic arterial pressure(SAP),diastolic arterial pressure(DAP),mean arterial pressure(MAP),heart rate(HR),stroke volume(SV),stroke volume index(SVI),cardiac output(CO),cardiac index(CI),stroke volume variation(SVV),pulse pressure variation(PPV).The positive standard was?SVI?10%[?SVI=(SVIT5-SVIT2)/SVIT2],divided the patients into response group(Rs)and non-response group(NRs).The observation indexes of the two groups were compared and analyzed.The primary endpoint is?SVI2ml/kg,?SVI1ml/kg[?OSVI2ml/kg=(SVIT4-SVIT2)/SVIT2??SVI ml/kg=(SVIT3-SVIT2)/SVIT2]and secondary endpoint is SVV,PPV.To calculate the sample size,we found the number of responders was twice as high as that of nonresponders according to the result of pilot trial.We therefore calculated that at least 42 patients were necessary,including 28 responders and 14 nonresponders using MedCalc software(two-tailed type I error at 5%,power equal to 80%,the minimum area under the ROC curve is 0.75,ratio of sample sizes in negative/positive groups at 1/2)All statistical analysis was computed by SPSS20.0 statistical software.Results were expressed as meanąstandard deviation if data were normally distributed or median(interquartile range)if not.Comparisons between responders and nonresponders were assessed using Student t test or the Mann-Whitney U test,as appropriate.Hemodynamic parameters were compared between supine and prone position using paired t test or the Wilcoxon test,as appropriate.Comparisons of hemodynamic parameters during volume expansion were assessed using the Friedman test or repeated measures analysis of variance,as appropriate.P value less than 0.05 was considered to be statistically significant.Receiver operating characteristic curves were generated for ?SVI1ml/kg,?SVI2ml/kg,SVV,PPV and areas under the receiver operating characteristics curves(95%CIs)were calculated and compared.The best cutoff value was determined according the Youden indexResults1.General informationA total of 48 patients were included in this study.The patients did not use vasoactive drugs before and during the trial,and completed the study successfully all of them.Rs group(n=30)and NRs group(n=18).There was no significant difference in general information between the two groups2.Hemodynamic indexesDuring volume expansion,there was no significant difference in HR,MAP,SVI,SVV and PPV between Rs group and NRs group.HR in the Rs group at T3,T4 and T5 were lower than that at T2(P<0.001);HR in NRs group was no difference at different time points.MAP in the Rs group only at T5 is higher than T2(P=0.025);MAP in NRs group was no difference at different time points.SVI in the Rs group at T3,T4 and T5 were higher than that at T2(P<0.001);SVI in NRs group was no difference at different time points.There was no significant difference in SVV at different time points in the group.PPV in the Rs group at T3,T4 and T5 were lower than that at T2(P<0.01);PPV in the NRs group was no difference at different time points.3.ROC curveThe AUC(95%CI)of ?SVI2ml/kg is 0.93(0.86-0.99),the diagnostic threshold is 8%,the sensitivity is 78%,and the specificity is 89%.The AUC(95%CI)of ?SVI1ml/kg is 0.87(0.77-0.97),the diagnostic threshold is 7%,the sensitivity is 80%,and the specificity is 83%.The AUC(95%CI)of SVV and PPV were 0.65(0.49-0.81)and 0.53(0.36-0.69),respectivelyConclusionMini-fluid challenge test can predict fluid responsiveness of prone position surgery in elderly patients under general anesthesia,and the predictive ability of rapid infusion of 2 ml/kg Crystalloid is stronger than 1 ml/kg. |
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