Limitations and Pitfalls of Continuous Arteriovenous Hemofiltration

Abstract

The driving force of arteriovenous hemofiltration is the blood pressure gradient between artery and vein. For this reason, a decompensated cardiac or circulatory failure places a limit on the use of this procedure. Adequate fluid withdrawal can only be obtained with systolic blood pressures higher than 60 mmHg, with a hematocrit below 40%, and rather low colloid-osmotic pressure. With a systolic blood pressure of 70 mmHg, filtration rates of 2-4 ml/min are observed. In our expierence, a low filtration rate of 180 ml/h is sufficient for the improvement of heart failure with low cardiac output (CO) in oligoanuric patients. In patients with cardiogenic shock, frequent thrombosis of the hemofilter may occur, but the overall elimination of fluid may be sufficient to improve the patient’s condition. Not infrequently, “prerenal kidney failure” exists in these patients and the excretion function of the kidney starts again, when cardiac output has slightly improved.