HDCN Article Review/Hyperlink

Steuer RR, Leypoldt JK, Cheung AK, Senekjian HO, Conis JM

Reducing symptoms during hemodialysis by continuously monitoring the hematocrit

Am J Kidney Dis (Apr) 27:525-532 1996

Hypotension represents a common problem in maintenance dialysis patients affecting 20-30% of all treatments. In some patients, there seems to be a critical blood volume level below which hypotension occurs [based on 20+ year old data]. Most methods to determine changes in blood volume during dialysis are inconvenient, not rapid and difficult to use. This article describes a method which monitors the hematocrit by a optical technique based on a sensor attached to the arterial blood line just proximal to the dialyzer. Changes in hematocrit can be used as a guide to changes in blood volume. Assuming that red cell mass remains constant, a given hematocrit level during a dialysis session may also represent a given level of total blood volume.

In the present study, the focus was on symptoms (lightheadedness, muscle crampling, and nausea, rather than on blood pressure per se. The hypothesis, based on preliminary study was, that such symptoms were associated with a patient-specific level of hypovolemia, as indicated by a critical hematocrit. In this unit, sodium gradient dialysis (150 to 140 mEq/L) is routinely used, with a constant UF rate. In an initial study, 6 patients were studied over 43 treatments, to determine a critical hematocrit level at which symptoms occurred. It is stated that the "symptom crit" was reproducible, with an SD of about 1.2 Hct units, although how often this "symptom crit" was reached in sessions without symptoms was not specified. One patient was dropped due to lack of symptoms

In phase two of the study, 5 patients were dialyzed either with a constant UF rate or with a step UF rate (initially 1.25% of the computed constant rate), which was then reduced (by 25%) when the previously determined "symptom crit" minus 2 Hct units was reached. The UF rate was then increased or decreased as needed to keep the Hct below the "symptom crit".

The postdialysis weight was not increased during dialyses with Hct- guided UF, and the number of sessons with intradialytic symptoms decreased from 16/28 (57%) to 7/27 (26%). It is concluded that Hct- guided UF reduces the incidence of nausea, lightheadedness, and muscle cramps. Interestingly, the maximum fall in MAP was not reduced using Hct-guided stepped UF vs. control sessions

Comment: This may be the simple volume measuring device that dialysis units need to assess "dry weight". It requires more testing in different units. This was a most provocative paper and should lead nephrologists to aggressively review dry weights in their hypertensive patients.

There are several caveats. Because the initial UF rate was increased, and a sodium gradient method was used, the symptomatic benefits may have been due to a non-linear UF rate rather than to Hct-control of UF rate. Also, the rationale for lumping together diverse symptoms such as lightheadedness, nausea, and muscle cramps is not clear. The symptoms were not analyzed separately. Finally, the number of patients (n=5) was quite small, and, as the control and experimental treatments were alternated, patient blinding was not done (Lionel Mailloux, M.D., North Shore University Hospital)