Continuous venovenous haemodiafiltration--an audit demonstrating control of electrolytes with haemodynamic stability in the critically ill.

OBJECTIVE

Renal replacement therapy has evolved significantly in the last 15 years, resulting in a large diversity of techniques with differing attributes. Theoretical advantages of the continuous over intermittent techniques in critically ill patients include haemodynamic stability and a reduction in disequilibrium syndrome. Limited clinical evidence supports this, but a clear reduction in mortality or morbidity has yet to be shown. The technique of renal replacement therapy in the Intensive Care Unit at Baragwanath Hospital was recently revised and a retrospective study of the haemodynamic and electrolyte changes associated with implementing continuous venovenous haemodiafiltration (CVVHD) was carried out.

METHOD

A retrospective analysis of demographic data, haemodynamic and physiological parameters in 10 consecutive patients receiving CVVHD during a 10-week period was conducted. Patients' systolic (SBP), and mean (MAP) arterial blood pressures, heart rates (HR), and central venous pressures (CVP) during the first 36 hours after the implementation of CVVHD were reviewed. Serum creatinine, urea and potassium values were also collated. Other organ system failures and outcomes were noted.

RESULTS

HR decreased by 6.1% (SD 1.5) and average MAP rose (12.1%; SD 7.8) as did SBP (12.4%; SD 6.3), compared with the values immediately before CVVHD: CVP was unchanged. Control of hyperkalaemia was effected in all cases. Serum urea and creatinine levels were well controlled, and clearances were closely related to the dialysate flow. Although the mortality rate was high, it was lower than predicted. No deaths were directly attributable to acute renal failure or complications of CVVHD:

CONCLUSION

In the critically ill, CVVHD provides excellent serum urea and creatinine clearance and control of electrolytes without further compromise of haemodynamics. The low associated morbidity, the ease of implementation and the efficacy of the technique may make CVVHD the technique of choice for ARF in the intensive care unit.