CRITICAL ROLE OF THE EXTRACORPOREAL BLOOD TEMPERATURE IN THE HEMODYNAMIC-RESPONSE DURING HEMOFILTRATION

Impaired vascular reactivity during combined ultrafiltration-hemodialy sis (UF + HD) compared with hemofiltration (HF) remains a rather enigm atic problem, the causes of which are still not well understood. Altho ugh a number of factors have been claimed to be responsible, most rece nt studies point to a major role of the extracorporeal blood temperatu re, which is usually lower during HF compared with UF + HD. However, p revious studies in which hemodynamics were studied during UF + HD and HF in relation to the extracorporeal blood temperature are limited by the use of acetate in UF + HD, and measurements were often confined to BP and heart rate, Therefore, arterial BP, as well as forearm vascula r resistance (FVR) and venous tone (strain-gauge plethysmography), was measured in 11 hemodialysis patients during 3 h UF + HD (37.5 degrees C) and predilution HF (39.0 degrees C = warm HF), resulting in equiva lent extracorporeal blood temperatures. Patients were also studied dur ing cold HF at an infusate temperature of 36.0 degrees C. UF + HD and HF were matched with respect to the dialysate and infusate composition (bicarbonate), biocompatibility factors, and small molecule clearance . At equivalent temperatures, UF + HD and HF were associated with a co mparable vascular and BP response. Only cold HF was associated with a significant increase in FVR. In addition, FVR and venous tone, as well as arterial BP, were all significantly higher during cold HF compared with both UF + HD and warm HF. These results indicate that the dispar ity in vascular reactivity between UF + HD and HF is primarily related to differences in the extracorporeal blood temperature.