Determination of the critical absolute blood volume for intradialytic morbid events

Abstract

The reduction of blood volume below a critical threshold is assumed to trigger intradialytic morbid events (IME). Recently, we presented a simple method to determine the absolute blood volume during routine hemodialysis (HD) carried out without blood sampling and without injection of dyes or radiolabeled markers. Such information could be used to detect excessive volume reduction during HD and to prevent IME. Therefore, we performed a pilot study in IME-prone patients to identify the absolute blood volume at which they developed clinical symptoms. A volume of 240 mL of ultrapure dialysate was automatically infused into the extracorporeal circulation using the bolus function of a commercial online hemodiafiltration machine incorporating a blood volume monitor (BVM). The increase in relative blood volume (RBV) caused by the infusion was measured and used to determine the absolute blood volume at that time. The blood volume per kilogram body mass at the time of symptomatic IME was also determined. All IME-prone patients of a single-dialysis center were included in the study. Ten out of 12 patients became symptomatic at a specific blood volume between 65 and 56 mL/kg (mean 62 mL/kg) whereas RBV showed a wide scatter (82-97%). A specific blood volume of 65 mL/kg seems to represent the threshold for IME by this method. The technique could be completely automated without altering the hardware of the dialysis device. Present feedback systems for automated blood volume-controlled ultrafiltration could be adapted to maintain absolute blood volume above this critical volume to safely prevent volume-dependent IME.

Vascular Refilling Is Not Reduced in Dialysis Sessions with Morbid Events

“…Blood volume, refilling volume, and UF volume from patients of a previous study [13] in which IME (symptomatic hypotension, severe cramps, loss of voice) occurred were analyzed at the onset of IME. At this time, UF was stopped and the times since the time the treatment was started as well as the RBV were recorded.…”

“…At this time, UF was stopped and the times since the time the treatment was started as well as the RBV were recorded. Symptoms and additional therapeutic measures are described in more detail elsewhere [13]. Two patients were diabetics and 7 patients had heart diseases (5 patients with coronary artery disease with stent implantation or myocardial infarction, 4 patients with impaired systolic function with an ejection fraction below 45%, and 1 patient with atrial fibrillation).…”

“…All patients gave written informed consent, and both studies [11,13] were approved by the Ethics Committee of the Berlin Medical Association.…”

“…When the absolute blood volume is known, vascular refilling volume can be calculated from the absolute change in blood volume, and from the known UF volume [12]. Recently, we performed a study on IME-prone patients to identify absolute blood volume at which they developed clinical symptoms [13]. In this study, we revisited the data of that previous study [13] to test the hypothesis whether vascular refilling was reduced in symptomatic dialysis treatments.…”

“…Recently, we performed a study on IME-prone patients to identify absolute blood volume at which they developed clinical symptoms [13]. In this study, we revisited the data of that previous study [13] to test the hypothesis whether vascular refilling was reduced in symptomatic dialysis treatments.…”