Continuous veno-venous haemofiltration following cardio-pulmonary bypass. Indications and outcome in 35 patients.

Objective: To study the impact of continuous veno-venous haemofiltration on survival in patients with acute renal failure (ARF) following cardio-pulmonary bypass (CPB) surgery.

Design: A retrospective study of all patients requiring haemofiltration after CPB over a 2 year period.

Setting: A 20 bedded, adult cardothoracic intensive care unit in a postgraduate teaching hospital.

Patients: 35 patients (26 male, age range 24-74 years) required haemofiltration (2.7% of the total number of patients undergoing CPB).

Main Results: Cardiovascular failure post CPB was the commonest causes of ARF (n = 16). Indications for haemofiltration were uremia (21), oligo-anuria (11), volume overload (2) and hyperkalaemia (1). Mean time from CPB to the initiation of haemofiltration was 8 days (range 0-15 days). Mean urea was 30 mmol/l and creatinine 362 mumol/l immediately prior to treatment. Urea was well-controlled in all patients, although 2 needed haemodiafiltration. Twenty-six patients died during their admission to the ICU (74% mortality). A further 3 patients died during their hospital admission, following discharge from ICU. Outcome was particularly poor in patients with cardiovascular failure following CPB (16 cases, 0 survivors). Survivors tended to commence filtration earlier (mean of 4 vs 7 days for non-survivors) and required treatment for a mean period of 8 days (range 1-26 days). Survival was determined by the number of failed organ systems at the start of haemofiltration. Thus, 100% of patients with single system failure survived, compared to only 10% with 3 or more system failure.

Conclusions: Despite the theoretical advantages of haemofiltration and the effective control of uraemia the mortality associated with ARF following CPB remains high and is probably determined by the number of failed organs systems.