Influence of postural changes on the variations of blood volume in hemodialysis and reincidence postdialysis blood volume

Abstract

The aim of the present work is to study the possible increment of blood volume, in the seated as well as the lying position, and to analyse the influence of changes of posture on the changes of blood volume during the hemodialysis. 17 patients were studied, evaluating the variations of the hematocrit in the extracorporeal circuit on entry into the dialyzer, by means of a photometric system (Crit-Line Instrument, Izasa). Every 15 minutes the values of the hematocrit were taken and heir repercussion in the blood volume in different changes of posture. Initially all of the patients improved their blood volume, both seated and lying down. During the session of hemodialysis and ultrafiltration, with the patient in a seated position, an important drop in the blood volume was noticed; this was the case in the 1st, 2nd and 3rd hours. This drop improved when the patient adopted a lying position and there was a "reincidence of post-dialysis blood volume" at the end. According to these results, the supine posture improves the refill, confirming that the patients position influences the vascular refill.