Effect of methylprednisolone versus placebo on the risk of acute kidney injury in 7286 patients undergoing cardiopulmonary bypass surgery
| Variable | No. (%) of events* | Relative risk (95% CI) | ||
|---|---|---|---|---|
| Methylprednisolone n = 3647 | Placebo n = 3639 | Unadjusted† | Adjusted‡ | |
| Acute kidney injury (primary definition)§ | 1479 (40.6) | 1426 (39.2) | 1.03 (0.98 to 1.09) | 1.04 (0.96 to 1.11) |
| Secondary definitions | ||||
| Acute kidney injury or death¶ | 1512 (41.5) | 1459 (40.1) | 1.03 (0.98 to 1.09) | 1.03 (0.96 to 1.11) |
| Stage 2 or higher acute kidney injury** | 360 (9.9) | 356 (9.8) | 1.01 (0.88 to 1.16) | 1.01 (0.87 to 1.17) |
| Stage 3 acute kidney injury†† | 145 (4.0) | 161 (4.4) | 0.90 (0.72 to 1.12) | 0.89 (0.71 to 1.12) |
| Acute dialysis within 30 d of surgery‡‡ | 95 (2.6) | 88 (2.4) | 1.08 (0.81 to 1.43) | 1.07 (0.80 to 1.43) |
Note: CABG = coronary artery bypass grafting, CI = confidence interval.
↵* A peak postoperative serum creatinine measurement was available for 99.1% of patients. Of 62 patients missing a peak postoperative value (31 in the methylprednisolone group and 31 in the placebo group), 2 received dialysis in the 30-day period after surgery and were coded as having acute kidney injury (1 in the methylprednisolone group and 1 in the placebo group). The remaining 60 patients were assumed to not have acute kidney injury; of these 60 patients, 50 (83.3%) died on the day of surgery or on day 1 or 2 after surgery (27/30 [90.0%] in the methylprednisolone group and 23/30 [76.7%] in the placebo group).
↵† A modified Poisson regression model was used without adjustment for covariates or accounting for centre.
↵‡ Adjusted for 10 prespecified covariates using a generalized estimating equation approach accounting for centre: age (yr); sex; left ventricular function < 50%; diabetes; preoperative estimated glomerular filtration rate < 60 mL/min/1.73m2; prerandomization use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, statins or diuretics; surgery type (isolated valve [referent], isolated CABG, CABG and valve, or other); and evidence of nonelective surgery (defined as preoperative use of inotropes or vasopressors, preoperative use of an intra-aortic balloon pump or ventricular assist device, or evidence of myocardial infarction in the 30 days before surgery).
↵§ Defined as an increase in serum creatinine concentration (from the preoperative value) of 0.3 mg/dL or more (≥ 26.5 μmol/L) or 50% or more in the 14-day period after surgery, or receipt of dialysis in the 30-day period after surgery.
↵¶ Met the primary definition of acute kidney injury or died within 48 hours of surgery. This was examined to account for the potential impact of early deaths on the ascertainment of acute kidney injury; early deaths occurred in 48 (1.3%) patients in the methylprednisolone group and in 47 (1.3%) patients in the placebo group.
↵** Defined as an increase in postoperative serum creatinine of 100% or more from the preoperative value or an increase to an absolute value of 4.0 mg/dL or more (≥ 353.6 μmol/L) (while meeting the primary definition) within 14 days of surgery, or (iii) receipt of dialysis within 30 days of surgery.
↵†† Defined as an increase in postoperative serum creatinine of 200% or more from the preoperative value or an increase to an absolute value of 4.0 mg/dL or more (≥ 353.6 μmol/L) (while meeting the primary definition) within 14 days of surgery, or receipt of dialysis within 30 days of surgery.
↵‡‡ Receipt of dialysis in the 30 days after surgery. In patients who received acute dialysis, the median increase in serum creatinine concentration from the preoperative to the postoperative value was 1.7 (interquartile range 1.1–3.0) mg/dL (153 [interquartile range 97–268] μmol/L).