| Background:Sufficient perfusion pressure is the prerequisite for maintaining normal organ function,mean arterial pressure(MAP)is one of the key determinants of perfusion pressure.Organs and regions within organs may have different perfusion pressure and pressure-flow relationships owing to adaptive response to chronic pathophysiologic change,even at the same MAP.Personalizing blood pressure management,promptly treat abnormal blood pressure and tailored based on individual patient physiology aiming at reducing postoperative adverse incidents is the ultimate purpose and goal for MAP manipulation.A large body of evidence had shown that intraoperative hypotension and the magnitude of MAP aberrations are independent factors for increasing postoperative complications.Intraoperative MAP levels is one of the leading factors for the occurrence of postoperative AKI(50%or 0.3mg/dl increase in serum creatinine during first 2 to 7 postoperative days defined by latest KIDGO criteria).It will prolong the length of stay and increase postoperative mortality.The autoregulation threshold depends on the basal level of blood pressue,tending to be higher in patients with prior history of chronic hypertension.It is well known that lenient MAP control(intraoperative hypotension or abrupt MAP aberrations)is detrimental to patients'welfare and outcome.The aim of this study is to investigate the optimal MAP level for elderly patients with chronic hypertension,which minimize the risk of postoperative AKI.Objective:To investigate whether different intraoperative MAP control affects the incidence of postoperative AKI in elderly hypertensive patients after major gastrointestinal surgery,and which level is optimal for elderly hypertensive patients.Methods:The authors conducted a prospective,randomized,multicenter and open label study of 678 elderly patients with chronic hypertension undergoing gastric cancer eradication surgery or colorectal cancer surgery.The recruited patients were randomly allocated into three MAP levels,namely,group ?(65 to 80 mmHg),group ?(80 to 95 mmHg)and group ?(95 to 110 mmHg).Perioperatively,central venous pressure was monitored and kept 8 to 12 mmHg.The MAP was titrated to target MAP goal within 5 minutes by vasoactive agents if deviated from the target level in the presence of appropriate volume status.Serum creatinine was assayed before surgery,end of surgery,2 and 7 postoperative days.Cystatin-C(Cys-C)and neutrophil gelatinase associated lipocalin(NGAL)were measured before surgery and 2nd postoperative day.The primary endpoint was the incidence of AKI during the first 2 to 7 postoperative days.The second outcome was complications during perioperative period.Multivariable logistic regression was performed to analyze risk factors contributing to AKI in this trial and recognize the exposure-outcome or causal relationship between MAP levels and postoperative AKI.Results:646 patients were included in intention to treat analysis.The overall incidence of postoperative AKI was 10.9%of 71 in 646 gastrointestinal major surgeries in elderly hypertensive patients.AKI occurred 6.3%of group ?,whereas in group ? and group ?had higher occurrence of AKI,13.5%and 12.9%respectively(P<0.001).AKI was associated with a longer intensive care unit admission stay of 3 days(P=0.025)and higher incidence of intensive care unit admission(P=0.015).Importantly,minor creatinine increases(?Cr 25 to 49%above baseline but below 0.3mg/dl)not meeting AKI criteria were also associated with higher incidence of intensive care unit admission.Contrary to common belief,AKI was not associated with longer postoperative length of stay(P=0.213)but only correlated with 28 days mortality.The amount of vasoactive agents consumed in Group ?(norepinephrine(3.9±1.0)mg and phenylephrine(700±202)?g and nitroglycerin(5.4±1.6)mg)were significantly higher than other two groups(P=0.001),consequently,it comes with more frequent intraoperative sinus bradycadia(9.5%)and premature atrial beats(7.1%)though no serious cardiovascular adverse events were observed(P<0.05).At 28 days,there was no significant difference in mortality among three groups,with death reported in 7 of 230 patients in group ?(3.0%),6 of 206 cases in group?(2.9%)and 8 of 210 patients in group?(3.8%)(P=0.067).Serum NGAL of postoperative 48 h had higher predictive value with area under curve(AUC)0.982(95%CI,0.973 to 0.992)for AKI,however,serum Cys-C had poor value only with AUC 0.489(95%CI,0.416 to 0.562)using receiver operating characteristic analysis.In this study,MAP level,blood loss and volume of red blood cells were the risk factors contributing to postoperative AKI after a forward stepwise multivariable logistic regression analysis.Conclusion:The overall incidence of postoperative AKI is 10.9%,intraoperative MAP level of 80 to 95 mmHg is optimal for elderly patients with chronic hypertension,conferring reduced incidence of postoperative AKI after gastrointestinal major surgery.Compared to serum Cys-C,postoperative serum NGAL had higher predictive value for AKI occurrence. |
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