MON-236 EXTERNAL CARDIAC PACING REVERSES OLIGURIC ACUTE KIDNEY INJURY IN A CARDIAC SURGICAL PATIENT (CASE REPORT)

Abstract

Acute kidney injury (AKI) is a common complication of cardiac surgery, and is associated with increased morbidity and mortality. It may have multiple causes including intraoperative renal ischaemia and reperfusion due to cardiopulmonary bypass, low postoperative cardiac output, and nephrotoxic drugs. Bradycardia as a cause of AKI has rarely been reported. We describe a cardiac surgical patient in whom onset of bradycardia on postoperative day 3 led to AKI, which then promptly resolved with external cardiac pacing. A 78-year old man underwent two vessel coronary artery bypass grafting with bioprosthetic aortic valve replacement and mitral valve repair, with a total cardiopulmonary bypass duration of 181 minutes. Postoperative AKI was attributed to prolonged intraoperative hypotension and the need for inotropic support for 6 hours postoperatively to maintain mean arterial blood pressure >65mmHg. By day 2, the serum creatinine had risen from 100umol/L preoperatively (estimated glomerular filtration rate 60mL/min/1.73m2) to 263umol/L, before falling slightly to 240umol/L early on day 3. Throughout this period, urine output was >2L/day, weight was stable at 1kg above the preoperative weight of 70kg, and serum potassium was between 4.8 and 5.3mmol/L. Late on day 3, a junctional bradyarrhythmia was noted on telemetry, 48 hours after external on-demand cardiac pacing had been ceased (with pacing wires left in situ). Urine output dropped to only 135mL in total over the next 12 hours, despite oral fluid resuscitation and intravenous furosemide. Median heart rate was 50 beats per minute, median blood pressure was 124/62mmHg, and the patient remained afebrile and alert. On day 4, serum creatinine had risen again to 354umol/L, and weight had increased by a further 2.5kg. External atrial pacing was recommenced, with a ventricular rate of 70 beats per minute, whereupon urine output increased immediately. Furosemide was ceased, and polyuria ensued with the creatinine plateauing at 336umol/L on day 5, before falling to baseline over the next 3 days. Pacing wires were removed on day 6 with the patient in atrial fibrillation at a ventricular rate of 80 beats per minute. There was no renal artery stenosis on Doppler imaging. Bradycardia, presumably with a secondary reduction in cardiac output, should be considered as a potential cause of AKI in the postoperative setting, especially if oligoanuria occurs. In this case, temporary resumption of external cardiac pacing led to complete renal recovery.