Timing of replacement therapy for acute renal failure after cardiac surgery

Acute renal failure (ARF) following cardiac surgery remains a significant cause of mortality. The aim of this study is to compare early and intensive use of continuous veno-venous hemodiafiltration (CVVHDF) with conservative usage of CVVHDF in patients with ARF after cardiac surgery.

Due to ARF, CVVHDF was required in two groups of a total of 61 adult patients (1.79% of all patients). Group 1 included 27 patients while Group 2 included 34 patients. CVVHDF was performed on Group 1 when creatinine level exceeded 5 mg/dL, or potassium level exceeded 5.5 mEq/L irrespective of the urine output. CVVHDF was performed on Group 2 when urine output was less than 100 mL within consecutive 8 hours, with no response to 50 mg furosemide with the supplementary criterion that urine sodium concentration should be >40 mEq/L before the administration of furosemide.

The mean elapsed time between the surgery and the initiation of CVVHDF was 2.56 +/- 1.67 days in Group 1 and 0.88 +/- 0.33 days in Group 2 (p = 0.0001). The mean intensive care unit (ICU) stay for Group 1 was 12 +/- 3.44 days and 7.85 +/- 1.26 days for Group 2 (p = 0.0001). ICU mortality rate was 48.1% for Group 1 and 17.6% for Group 2 (p = 0.014). The overall hospital mortality rate was 55.5% for Group 1 and 23.5% for Group 2 (p = 0.016).

Recognition of ARF and early beginning of the CVVHDF are extremely important. The sooner the ARF after surgery is recognized and CVVHDF is performed, the higher the likelihood of the reduction of the hospital mortality.