The association of acute kidney injury with hospital readmission and death after pediatric cardiac surgery

Abstract

Background: Acute kidney injury (AKI) in children undergoing cardiac surgery (CS) is strongly associated with increased hospital mortality and length of stay. The association of AKI with postdischarge outcomes is unclear. We evaluated the association of AKI with all-cause readmissions and death within 30 days and 1 year of CS discharge. Methods: This was a prospective, 3-center cohort study of children after CS with cardiopulmonary bypass. The primary exposures were postoperative stage 1 AKI and stage 2 AKI defined by Kidney Disease: Improving Global Outcomes AKI definition. Two separate outcomes were hospital readmission and death within 30 days and 1 year of discharge. Association of AKI with time to outcomes was determined using multivariable Cox-proportional hazards analysis. Age, The Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery risk adjustment tool score 3, cardiopulmonary bypass >120 minutes, and cyanotic heart disease were evaluated as effect modifiers. PERSPECTIVE Reducing postoperative readmission and death is a priority. This is the first prospective cohort study to evaluate the relationship between AKI and post-cardiac surgery discharge readmission in children. Identifying risk factors for readmission and death may enable targeted follow up of atrisk groups and potentially decrease long-term morbidity and mortality. See Commentaries on pages 86 and 88.

Acute Kidney Injury in Critically Ill Children Is Not all Acute: Lessons Over the Last 5 Years

“…This has not only allowed us to identify AKI as an important risk factor for poor long-term outcomes, but it has also allowed us to quantify the magnitude of risk of developing these outcomes. Over the past 5 years, more data has been published beyond early mortality (within 28-days) describing both medium (1-2 year) (6,15,16,18) and long-term mortality risk (>3 years) (17,19). Importantly, only two studies evaluated post-discharge mortality (i.e., excluded hospital mortality from the index admission).…”

“…Two studies specifically focused on mortality in children with AKI following cardiac surgery. In a multicenter study of over 400 patients, Nune et al found that children with severe AKI post-cardiac surgery had over 11 times higher risk of mortality 30-day after surgery, following adjustment for age, surgical risk score, cardiopulmonary bypass time, and cyanotic heart disease (18). In a similar-sized population, Hirano…”

“…Previous studies evaluating short-and long-term mortality following AKI lacked non-AKI comparison groups, however, they uniformly highlight that mortality rates in patients with AKI were higher than in the general population (12,13). Since 2015, we identified eight studies that examined the association of AKI with mortality and compared this to children who did not develop AKI, with follow-up ranging from 28-days to 5-7 years (Table 1) (3,6,(14)(15)(16)(17)(18)(19). As highlighted in Table 1, despite differences in study populations and duration of followup, all studies reported higher mortality in those with AKI when compared with children who did not experience AKI whilst in the PICU, independent of illness severity and other important confounders.…”

“…Two studies specifically focused on mortality in children with AKI following cardiac surgery. In a multicenter study of over 400 patients, Nune et al found that children with severe AKI post-cardiac surgery had over 11 times higher risk of mortality 30-day after surgery, following adjustment for age, surgical risk score, cardiopulmonary bypass time, and cyanotic heart disease ( 18 ). In a similar-sized population, Hirano et al reported a higher risk of 2-year mortality in children with AKI [defined by Pediatric Risk, Injury, Failure, Loss, End Stage Renal Disease (pRIFLE) criteria] post-cardiac surgery [adjusted hazard ratio (95% CI): 7.47 (2.88–19.40)] ( 16 ).…”

“…In the cardiac surgery population, neither any AKI (i.e., stage 1, 2, or 3) nor severe AKI (stage 2 or 3 by KDIGO criteria) were associated with 30-day or 1-year hospital readmission ( 18 ). Unlike the aforementioned study in the non-cardiac population which evaluated the number of events per person-time (count data), this study focused on readmissions as a binary outcome.…”