Introduction: Acute renal failure (ARF) is a severe complication occurring in 4-15% after heart surgery. Preoperative renal dysfunction, advanced age and the duration of the procedure are known to increase the risk. One mechanism is the cytokine mediated inflammatory response in association with free oxygen radical formation during ischaemia and reperfusion. The free oxygen radicals are inactivated by glutathione peroxidase, which can be increased by N-acetylcysteine (NAC). NAC reduces the ARF caused by iopromide and acute liver failure. NAC may be beneficial in aortic surgery. No studies exist using NAC for renal protection in cardiac surgery. We studied the effects of intravenous NAC on renal function during and after open heart surgery in a randomized blinded and placebo controlled manner.
Method: Informed consent was obtained from 20 patients with serum creatinine above >110 μmol L−1, scheduled for elective open heart surgery with CPB. Patients already on haemodialysis or at a predialysis state were excluded. Anaesthesia was standardized. Haemodynamics were controlled with norepinephrine, epinephrine and fluids on request. At the induction of anaesthesia either NAC or 0.9% NaCl infusions were started. NAC was given as a loading dose of 150mg kg−1 followed by 50 mg kg−1 for the next 4h and thereafter 100mg kg−1 for 16 h. Serum creatinine, urine N-acetylbetaglucosaminidase (NAG), alpha-1-microglobulin and serum cystatin-C (cyst) were measured before the operation, during the procedure and postoperatively. The total volumes of fluids given and urine excreted during 24 h after surgery were recorded. T-test was used for statistics.
Results: No differences were found in the demographics, types of procedures or haemodynamics between the groups. No side effects by NAC were observed. NAG and alpha-1-microglobulin concentrations will be presented later.
The mean total volumes of urine excreted were 3358 and 2553 mL and the mean total volumes of fluids infused during 24 h after operation were 16260 and 13668 ml in the NAC and NaCl groups, respectively.
Discussion: No patient was dialyzed. No complications occurred. No significant differences in the renal function were found between the groups, yet in the NAC group serum creatinine decreased while in the placebo group it increased by day 3 after surgery. More urine was excreted in the NAC group. A larger group of patients will be collected to increase the power of the study.
1 Tepel et al. Prevention of radiographic-contrast-agent-induced reductions in renal function by acetylcysteine. NEJM