Study On Oxygen Delivery Index During Extracorporeal Circulation And Acute Kidney Injury After Cardiac Surgery In Low-birth-weight Infant

Background:Acute kidney injury(AKI)is one of the most common complications after pediatric cardiac surgery undergoing cardiopulmonary bypass(CPB),and is significantly associated with other perioperative adverse outcomes.Indexed oxygen delivery(DO2i)during CPB is an independent risk factor for postoperative AKI.Currently,the DO2i threshold for preventing postoperative AKI in low weight infants(≤10 kg)has not been well studied.Therefore,the main objective of this study was to investigate the association between postoperative AKI and DO2i during CPB in low weight infants.Methods:This is a prospective observational study enrolling low weight infants(≤10 kg)undergoing cardiac surgery with CPB from August 2021 to July 2022.DO2i was calculated by intermittent intraoperative blood gas analysis in combination with real-time perfusion flow rate,and the lowest DO2i level was obtained during the hypothermic and re warming phases of CPB,respectively.The patients were divided into mild hypothermia group(32-34℃)and moderate hypothermia group(26-31℃)according to the lowest intraoperative rectal temperature,and the association between the lowest DO2i and postoperative AKI was analyzed using receiver operator characteristic(ROC)curves and multifactor logistic regression in the two groups.Results:During the study period,clinical data form 371 low weight infants were collected.A total of 142 patients(38.3%)presented with postoperative AKI.Infants with AKI had lower height,preoperative hemoglobin and serum creatinine levels(P<0.05).There was no statistical difference in other demographic and baseline characteristics.The lowest DO2i values in infants with AKI were significantly lower in hypothermia phase(247.18 ± 35.84 vs 256.15±41.48,P=0.034)and rewarming phase(269.77 ±37.35 vs 286.85 ± 40.63,P<0.001)during CPB.A total of 218 infants experienced mild hypothermia during CPB,and 153 infants experienced moderate hypothermia,with no statistically significant difference in the incidence of postoperative AKI between groups(P=0.335).In mild hypothermia group,DO2i during hypothermia and rewarming phases was associated with postoperative AKI(P=0.001),with optimal thresholds of 258 and 281 mL/min/m2,respectively.After adjusting for age,weight,and other influence factors in logistic regression,the lowest DO2i<258 mL/min/m2 during hypothermia(OR 3.012,95%CI 1.635-5.548,P<0.001)and the lowest DO2i<281 mL/min/m2 during rewarming(OR 3.246,95%CI 1.767-5.963,P<0.01)were independent risk factors for postoperative AKI.When both were brought into the model,only DO2i during rewarming remained in the final model.The lowest DO2i during rewarming also showed a higher predictive probability for postoperative AKI(ROC-AUC:0.653 vs 0.637).However,no statistically significant correlation was found between postoperative AKI and the lowest DO2i during hypothermia or rewarming phases in the moderate hypothermia group.Conclusion:In low weight infants undergoing cardiac surgery with mild hypothermic CPB,the critical DO2i threshold for preventing postoperative AKI is 258 mL/min/m2 during hypothermia and 281 mL/min/m2 during rewarming.More attention should be paid to the balance of oxygen delivery and demand during the rewarming phase,and the application of individualized critical DO2i threshold is advocated during CPB.Background:Acute kidney injury(AKI)is a common complication after cardiac surgery with cardiopulmonary bypass(CPB)in children,especially in low weight infants with immature organ systems.It can affect short-and long-term clinical outcomes.Various diagnostic criteria exist for AKI in children,such as pediatric-modified Risk,Injury,Failure,Loss,and End-Stage(pRIFLE),and Kidney Disease:Improving Global Outcomes(KDIGO).The recently proposed pediatric reference change value optimized for AKI in children(pROCK)combines the high variability of serum creatinine in children to improve the detection of "true" AKI.However,no study has validated pROCK as a diagnostic criterion for postoperative AKI in infants undergoing cardiac surgery.This study aimed to assess the incidence of postoperative AKI and its correlation with clinical outcomes in low weight infants undergoing cardiac surgery,based on the three diagnostic criteria:pRIFLE,KDIGO,and pROCK.Methods:This study is a secondary analysis of the database developed in Section 1,including clinical data from low weight infants(≤10 kg)who underwent cardiac surgery with CPB from August 2021 to July 2022.AKI was defined and staged according to the three diagnostic criteria of pRIFLE,KDIGO,and pROCK,respectively.The differences in AKI incidence between different diagnostic criteria,as well as the consistency of diagnosis and staging were assessed.Additionally,the correlation between AKI defined by the three diagnostic criteria and clinical outcomes was assessed by Kaplan-Meier curves and multifactor logistic regression.Results:A total of 413 infants were included,of whom 185(44.8%),160(38.7%),and 77(18.6%)were diagnosed with postoperative AKI according to pRIFLE,KDIGO,and pROCK,respectively.There was a significant difference in the overall incidence of AKI among the three diagnostic criteria(P<0.001),especially in patients with baseline creatinine ≤ 30μmol/L,the incidence of postoperative AKI was 55.5%,49.6%,and 23.7%,respectively(P<0.001).In terms of the agreement in the diagnosis of AKI,a high agreement of 93.9%(κ=0.88)was shown between pRIFLE and KDIGO,whereas the pROCK criteria showed only moderate agreement with the above two.In addition,the three diagnostic criteria showed a large difference in terms of agreement for AKI staging,with pRIFLE and KDIGO still showing a high agreement of 89.8%(κ=0.82),while pROCK criteria were only 65.1%(κ=0.29)and 69.5%(κ=0.33)consistent with them.As for postoperative clinical outcomes,the incidence of adverse outcomes was higher in patients with pROCK-AKI(16.9%vs 5.4%,P=0.001).After adjusting for age,weight,and CPB duration in the multifactor analysis,pROCK-AKI was the independent risk factor for the composite of adverse outcomes(OR 3.293,95%CI 1.487-7.292,P=0.003)and prolonged mechanical ventilation(OR 3.211,95%CI 1.530-6.738,P=0.002).However,there was no significant correlation between in-hospital adverse clinical outcomes and AKI defined by pRIFLE and KDIGO(P>0.05).Conclusion:The incidence and staging of AKI after cardiac surgery with CPB in low weight infants varied considerably according to different diagnostic criteria.AKI defined by pROCK had a significantly lower incidence compared with pRIFLE and KDIGO criteria,and more correlated with postoperative clinical outcomes,which is expected to improve the detection of "real" AKI after cardiac surgery in children.