慢性血液透析患者における全身総カリウム量と血球内カリウムに関する研究

Abstract

The present studies were designed to detect changes in body potassium content in patients being hemodialyzed on a chronic basis. Twelve patients were studied on 29 occasions. Measurements were made both before and after eight hours of hemodialysis against a bath containing 2mEq/L of potassium. Total body potassium was determined using a whole body counter. Erythrocyte potassium concentration and plasma potassium concentration were measured using a flamephotometer. The patients were classified into four groups on the basis of their predialysis total body potassium values. Comparisons were made between groups of patients of approximately the same sex and the same age. The groups were: 1) Two patients had distinctly elevated total body potassium (H group). 2) Four patients had total body potassium value in the high normal range (N( +) group). 3) Five patients had total body potassium values which were in the low normal range (N( -) group). 4) Four patients had total body potassium values which were distinctly lower than normal (L group). Repeated estimations of total body potassium in individual cases showed little variation. Total body potassium values were increased following hemodialysis in almost all cases in each group. Plasma potassium concentrations decreased during hemodialysis in all cases and a fall in erythrocyte potassium concentration was demonstrated in about half of the studies. Changes in total body potassium from predialysis values were most marked in the L group. Erythrocyte potassium concentration decreased somewhat in the H group during hemodialysis. There was a good correlation between the changes in total body potassium and changes in erythrocyte to plasma potassium concentrations in all groups. In order to examine the kinetics of potassium movement into red blood cells, 42K influx studies were performed in five anuric patients. On the day that the patients were not dialyzed, 42K influx was considerably higher in the L group than in the N group. Similar studies performed on the days that these patients were dialyzed showed an increase in 42K influx in the L group and decreased 42K influx as well as increased 42K efflux during hemodialysis in both N groups. There were no significant relations between changes in acid base balance and changes in total body potassium and erythrocyte potassium during the period of study. The small changes in total body potassium which we detected during hemodialysis were not significant statistically. While it seems possible that potassium movements between body compartments might occur during hemodialysis, the present studies did not allow us to distinguish between the direction of these movements. Of interest is the fact that potassium influx into red cells in vitro, seem to be a function of pre-existing total body potassium stores. If a similar change occurred during hemodialysis, one would expect an increase in intracellular potassium, and an increase in total body potassium. However, it may be that the methods employed are not sensitive to pick up the small changes which could occur, since total body potassium stores may be estimated at over 3, 000 mEq. We conclude that predialysis total body potassium value is a useful index of the direction and magnitude of changes which may occur during hemodialysis. Total body potassium content may be useful in predicting direction and degree of potassium movement between intra- and extracellular components.