Deciding When to Start Renal Replacement Therapy After Cardiac Surgery in Real Life

Abstract

Acute kidney injury (AKI) is a frequent complication of cardiac surgery that contributes to postoperative morbidity and mortality. The timing of renal replacement therapy (RRT) remains unclear.1Corredor C Thomson R Al-Subaie N. Long-term consequences of acute kidney injury after cardiac surgery: A systematic review and meta-analysis.J Cardiothorac Vasc Anesth. 2016; 30: 69-75Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar,2Chew STH Hwang NC. Acute kidney injury after cardiac surgery: A narrative review of the literature.J Cardiothorac Vasc Anesth. 2019; 33: 1122-1138Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar The Artificial Kidney Initiation in Kidney Injury (AKIKI) trial and the Standard versus Accelerated Initiation of Renal-Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial, 2 randomized clinical trials conducted in the intensive care unit (ICU), showed no difference in mortality between an early or delayed strategy of initiation of RRT.3Gaudry S Hajage D Schortgen F et al.Initiation strategies for renal-replacement therapy in the intensive care unit.N Engl J Med. 2016; 375: 122-133Crossref PubMed Scopus (638) Google Scholar,4STARRT-AKI InvestigatorsCanadian Critical Care Trials GroupAustralian and New Zealand Intensive Care Society Clinical Trials GroupTiming of initiation of renal-replacement therapy in acute kidney injury.N Engl J Med. 2020; 383: 240-251Crossref PubMed Scopus (201) Google Scholar However, these studies mainly included patients with sepsis. The Early versus deLAyed Initiation (ELAIN) of RRT in critically ill patients with AKI study, which mostly included postoperative cardiac surgery patients in its population, showed a decrease in mortality for early initiation of RRT.5Zarbock A Kellum JA Schmidt C et al.Effect of early vs delayed initiation of renal replacement therapy on mortality in critically ill patients with acute kidney injury: The ELAIN randomized clinical trial.JAMA. 2016; 315: 2190-2199Crossref PubMed Scopus (650) Google Scholar We note that STARRT-AKI and AKIKI found a decrease in RRT rate of 35% and 51%, respectively, in the delayed strategy group. On the contrary, there was no such decrease in ELAIN, with a 92% RRT rate in this group. In our cardiothoracic ICU, the physicians' practice is to start RRT late. We performed a retrospective, observational, single-center study of patients in the cardiothoracic ICU of the University Hospital of Limoges to compare the proportion of RRT if the early criteria of the ELAIN, AKIKI, and STARRT-AKI studies had been chosen. All patients who developed AKI at least stage 2 according to the Kidney Disease Improving Global Outcomes (KDIGO) classification based on creatinine levels within a week after cardiac surgery were included. Patients with a history of renal transplantation or chronic kidney disease were excluded. Of 978 patients who had been treated in our institution, 65 patients met the inclusion criteria. Demographics are provided in Table 1. Of these patients, 32 (49%) did not progress to KDIGO Stage 3 and did not require RRT, 13 (20%) progressed to KDIGO Stage 3 without RRT, and 20 (31%) progressed to KDIGO Stage 3 and required RRT. However, if we had applied the criteria for early RTT of the ELAIN and STARRT-AKI studies, all 65 patients would have required RRT. Therefore, we were able to avoid treating 45 patients (69%) with RRT (Fig 1, A). Similarly, with the early strategy criteria of the AKIKI study (KDIGO 3 patients), 33 (51%) patients would have received RRT, whereas this intervention has been avoided in 13 patients (39%) (Fig 1, A). These results were similar to those of the STARRT-AKI and AKIKI studies but not to ELAIN. Survival among patients with and without RRT was similar (Fig 1, B).Table 1DemographicsCharacteristicsOverall N = 65RRT N = 20Without RRT N = 45pAge, y69 (64-75)71.5 (63-73.5)68 (64-75)0.77Emergency29 (45)9 (45)20 (44)0.99Previous cardiac surgery7 (10)2 (10)5 (11)0.99CPB duration, min100 (60-182)148 (80-199)122 (79-194)0.83Cross-clamp duration, min45 (72-110)90 (57-115)84 (48-126)0.98Hemolysis18 (28)10 (50)8 (18)0.015Surgical revision8 (12)2 (10)6 (13)0.99History of high blood pressure36 (55)10 (50)26 (58)0.60History of diabetes18 (28)5 (25)13 (28)0.99Preoperative LVEF, %55 (48-62)55 (48-69)55 (46-61)0.51Creatinine before surgery, µmol/L85 (70-95)90 (78-102)84 (68-93)0.08Higher creatinine, µmol/L247 (186-417)469 (385-604)210 (173-248)< 0.0001Urea nitrogen, mmol/L19.5 (15-25.6)25 (20-33)17 (13-24)0.0004Creatinine at day 7, µmol/L175 (109-267)268 (180-392)140 (99-215)0.0003Creatinine at discharge of ICU, µmol/L135 (100-232)220 (141-289)117 (88-152)0.002KDIGO 333 (51)20 (100)13 (29)< 0.0001Duration of RRT, dNA4.5 (3.75-6.25)0NAPotassium, mEq/L5.5 (5-6)5.75 (5.5-6.1)5.4 (4.9-5.9)0.1Postoperative pH7.26 (7.19-7.3)7.2 (7.17-7.26)7.28 (7.21-7.32)0.014Postoperative base deficit4 (3-6)5 (4-6)3.5 (1.9-5.3)0.025Mechanical ventilation >48 h30 (46)15 (75)15 (33)0.003Postoperative length of stay in ICU and intermediate care unit, d14 (9-22)23.5 (17-34)11 (8-16)< 0.0001Mortality12 (18)6 (30)6 (13)0.17NOTE. The continuous variables are presented as median and IQR (Q1-Q3). The categorical variables are presented as number (proportion). The 2 groups were compared using Mann-Whitney U test for continuous variables and the chi-square test or Fisher exact test for the categorical variables.Abbreviations: CPB, cardiopulmonary bypass; ICU, intensive care unit; KDIGO, Kidney Disease Improving Global Outcomes; LVEF, left ventricular ejection fraction; RRT, renal replacement therapy. Open table in a new tab NOTE. The continuous variables are presented as median and IQR (Q1-Q3). The categorical variables are presented as number (proportion). The 2 groups were compared using Mann-Whitney U test for continuous variables and the chi-square test or Fisher exact test for the categorical variables. Abbreviations: CPB, cardiopulmonary bypass; ICU, intensive care unit; KDIGO, Kidney Disease Improving Global Outcomes; LVEF, left ventricular ejection fraction; RRT, renal replacement therapy. None.