Membrane biocompatibility: effects on cardiovascular stability in patients on hemofiltration

We investigated the effect of membrane bio-incompatibility on cardiovascular stability in 10 patients with combined acute hepatic and renal failure during 44 isovolemic intermittent machine hemofiltration treatments, using a polyamide membrane in 24 and a polyacrylonitrile membrane in 20. Cardiac output decreased by 14 +/- 2% during polyamide treatment compared to 8 +/- 3% during polyacrylonitrile (P < 0.05). Pulmonary artery occlusion pressure decreased by 20% or more in 65% of the polyamide treatments compared to 38% of the polyacrylonitrile (P < 0.05). Tissue oxygen delivery decreased by 16 +/- 2% during polyamide treatment compared to 6 +/- 3% during polyacrylonitrile treatment (P < 0.05). Mean arterial blood pressure declined from 80 +/- 3 mm Hg to 70 +/- 2 mm Hg during polyamide treatment (P < 0.001), whereas there was no significant change during polyacrylonitrile treatment. Thus, in this group of critically ill patients, the use of two different membranes was associated with greater cardiovascular stability with polyacrylonitrile treatment compared to polyamide, with respect to maintenance of tissue perfusion and perfusion pressure. This suggests that extracorporeal membrane bio-incompatibility may have a role in determining cardiovascular stability during treatment with extracorporeal circuits.