Carnitine action on red blood cell osmotic resistance in hemodialysis patients

Low red blood cell osmotic resistance (RBCOR) in dialysis patients aggravates anemia and raises EPO needs. We studied RBCOR in 30 stable patients (22 M, 8 F), dialyzed for more than one year, with no systemic illness, blood transfusions, recent infection or treatment by ACE inhibitors. Nineteen were on EPO. Cuprophane dialysis membranes were used in 21, synthetic in the remaining nine. RBCOR was low in 13 patients and these patients received L-carnitine, 20 mg/kg IV, post dialysis, for one year (A); 17 with normal RBCOR served as untreated controls (B). We investigated the relations between RBCOR and membrane material, time on HD (THD), weekly dialysis duration (WHDT), serum total carnitine (TC), acyl carnitine (AC), free carnitine (FC) and AC/FC in all patients, before and after carnitine supplementation. RBCOR changes under carnitine treatment were evaluated. Age, sex, primary renal disease, THD, EPO dose, hematology and biochemistry were similar in treated patients and controls. Patients in group A (dialysed with cuprophane) had lower RBCOR than group B, (dialysed with synthetic and cuprophane membranes) (0.473 +/- 0.02 vs. 0.420 +/- 0.02, P < 0.001). RBCOR remained stable under carnitine in group A, but became abnormally low in controls (especially in 10/17 patients). RBCOR was significantly higher than the pretreatment values in 5/13 group A patients (month 0-M0: 0.48 +/- 0.02, M12: 0.45, +/- 0.02, P < 0.05). Carnitine levels, similar in both groups before treatment, remained stable in group A, but dropped in group B (TC: 52.1 +/- 9.6/31.1 +/- 21.2, FC: 33.1 +/- 8.3/15.6 +/- 19.2 micromol/L, P < 0.002). Patients with shorter WHDT (< or = 12 vs. > 12 h) had higher FC levels (36 +/- 6.9 vs. 30 +/- 6 micromol/L, P < 0.03). Low RBCOR is frequent in stable dialyzed patients. It is related to dialysis membranes and is aggravated by time on hemodialysis. Serum carnitine levels depend on weekly dialysis time and on carnitine supplementation, that normalizes osmotic resistance in some dialysis patients.