Acute kidney injury after coronary artery bypass grafting: does rhabdomyolysis play a role?

OBJECTIVE

In clinical situations in which rhabdomyolysis is common, renal dysfunction association with myoglobinemia is well described. After coronary artery bypass grafting, a rapid increase in serum myoglobin concentration is generally seen, but whether it might independently increase the risk of acute kidney injury remains to be determined.

METHODS

The study population consisted of 731 consecutive patients undergoing coronary artery bypass grafting. Creatine kinase, myoglobin, and creatinine concentrations were assessed in each patient preoperatively and postoperatively. Acute kidney injury was defined as an absolute increase in serum creatinine concentration of 0.3 mg/dL or greater.

RESULTS

Overall, 295 (40.3%) of 731 patients had acute kidney injury. Patients' risk profiles were significantly worse in those with acute kidney injury, and 31 (4.2%) of 731 patients required dialysis. Acute kidney injury was associated with a higher increase in serum myoglobin concentration after 1 hour from aortic declamping (534 microg/mL [interquantile range, 354-733 microg/mL] vs 377 microg/mL [interquantile range, 278-528 microg/mL], P < .0001), which persisted at 24 and at 48 hours. After adjusting for confounding factors, myoglobin concentration was found to independently predict postoperative acute kidney injury (odds ratio, 1.0011 [1 microg/mL increase]; 95% confidence interval, 1.0003-1.0019; P = .005), and this result persisted when patients with perioperative myocardial infarction were excluded from the analysis (odds ratio, 1.0007; 95% confidence interval, 1.0002-1.0009; P = .01). Myoglobin concentration had a better accuracy to discriminate patients having acute kidney injury than creatine kinase concentration at any time.

CONCLUSIONS

An increase in laboratory findings of muscle injury postoperatively, especially serum myoglobin concentration, predicts the incidence of acute kidney injury and renal replacement therapy requirement, as reported in other surgical settings. Perioperative myocardial injury cannot totally explain the occurrence of increased myoglobinemia. These results suggest an important role of skeletal muscle breakdown and necrosis in determining an increased myoglobinemia concentration after coronary artery bypass grafting.