Risk factors and outcome of rhabdomyolysis after cardiac surgery

Introduction

Rhabdomyolysis is a dissolution of skeletal muscles causing extravasation of toxic intracellular contents from the myocytes into the circulatory system. It leads to electrolyte disturbances, hypovolemia, and renal failure. The incidence of rhabdomyolysis after cardiac surgery and the impact on prognosis are not known. The purpose of this study was to determine the incidence of rhabdomyolysis, the associated risk factors and to assess the prognostic impact in patients undergoing cardiac surgery.

Methods

We performed a prospective, observational study in a tertiary surgical ICU in a university hospital. A total of 200 patients undergoing elective surgery were evaluated. Creatine kinase (CK) samples were collected daily (rhabdomyolysis, CK > 2,500 U/l) as plasma creatinine, CK-MB and troponin. Patients were followed during the ICU stay and clinical outcomes were evaluated. Renal failure was defined as >50% increase in serum creatinine from baseline, and myocardial ischemia as an increase of CK-MB or troponin greater than five times.

Results

Rhabdomyolysis was present in 38 patients (19%). There were no relations between rhabdomyolysis and hypothermia, sex, age, cardioprotection or use of vasoactive drugs. Risk factors were: previous use of statin (P = 0.002), intraoperative hemodynamic instability (P = 0.045), longer duration of surgery (P < 0.001), and longer duration of pump (P < 0.0001). The previous use of statin and a longer duration of surgery were independent predictors of rhabdomyolysis (statin OR = 3.68, 95% CI = 1.38–9.83 and longer duration of surgery (minutes) OR = 1.01, 95% CI = 1.006–1.02). The occurrence of rhabdomyolysis was not associated with higher incidence of renal failure, myocardial ischemia, mortality and longer time of ICU stay.

Conclusion

In this observational study, rhabdomyolysis was a frequent event after cardiac surgery, present most in patients with previous use of statin or who presented hemodynamic instability in the intraoperative period. However, this had no implications with respect to midterm prognosis.