Quantitative assessment of carnitine loss during hemodialysis and hemofiltration

Carnitine deficiency has been claimed to be responsible for the myo- and cardio-myopathy observed in dialysis patients and has been attributed to the loss of carnitine during dialysis. To quantitate carnitine loss, we determined the carnitine concentrations in 29 patients on chronic hemodialysis, 10 patients on chronic hemofiltration, and 8 patients on CAPD. Mean plasma carnitine levels in hemodialysis and hemofiltration patients (39.8 +/- 2.7 mumoles/liter; N = 39) were significantly lower (P less than 0.01) than in controls (49.8 +/- 2.0 mumoles/liter; N = 43). Hemodialysis or hemofiltration led to a further reduction (33.2 +/- 3.5 mumoles/liter; P less than 0.001). There was no significant difference in the mean plasma carnitine level between CAPD patients (40.0 +/- 5.7 mumoles/liter) and controls. Hemofiltration treatment resulted in a weekly loss of 795 +/- 84 mumoles of carnitine. This was significantly lower (P less than 0.0001) than the urinary carnitine excretion in healthy controls (1534 +/- 134 mumoles per week; N = 27) and the carnitine elimination in the dialysate of CAPD patients (1905 +/- 236.6 mumoles per week; N = 8). It is concluded that carnitine deficiency in dialysis patients cannot be explained by loss into dialysate or filtrate. Because intestinal reabsorption of carnitine does not seem to be impaired, decreased endogenous carnitine synthesis is considered as the most plausible explanation for the moderate degree of carnitine deficiency observed in dialysis patients.