Haemolysis in haemodialysis patients: evidence for impaired defence mechanisms against oxidative stress

Background. Uraemic patients have a decreased ability to withstand oxidativ e stress. It is postulated that their antioxidant capacity is reduced, yet the mechanism remains unclear. Recently 33 haemodialysis (HD) patients were exposed to chloramine contamination in the water supply. This led to haemo lysis in 24 patients, while nine were unaffected. In the former group haemo globin decreased from 11.7+/-l.l to 8.5+/-1.4 g/dl (P<0.0001) and returned to 11.4+/-0.9 g/dl (P<0.0001) following recovery. During haemolysis, haptog lobin was 38.4+/-10.6 vs 138.1+/-8.3 ng/dl (P<0.0001) following recovery. Methods. To explore the factors affecting the severity of haemolysis we stu died extracellular and intracellular anti-oxidant defence mechanisms 3 mont hs after recovery. In 29 patients and 20 controls we determined plasma glut athione (GSH), and the erythrocyte enzymes glutathione peroxidase (GSH-Px), glutathione reductase (GSH-Rx), and superoxide dismutase (SOD). Serum malo ndialdehyde (MDA) was measured as a marker of oxidative stress. Results. Plasma GSH was lower in patients as compared to controls (5.49+/-0 .26 vs 7.4+/-0.5 mu mol/l, P<0.005). There was an inverse correlation betwe en GSH and the degree of haemolysis (r = -0.42, P<0.02). Patients had highe r GSH-Rx (4.64+/-0.15 vs 3.97+/-0.12 U/gHb, P<0.02), lower GSH-Px (29.7+/-1 .85 vs 35.5+/-1.62 U/gHb, P<0.001), and similar SOD (0.63+/-0.02 vs 0.51+/- 0.02 U/mgHb) as compared to controls. There was no correlation between the enzyme levels and the degree of haemolysis. MDA was higher in patients (2.3 7+/-0.07 vs 0.97+/-0.1 nmol/ml, P<0.0001). There was a correlation between MDA and the years patients were on HD (r = 0.43, P<0.02). Conclusions. These data indicate that HD patients have an impaired anti-oxi dant response, which may be attributed in part, to plasma GSH deficiency. P atients with the lowest plasma GSH levels are more susceptible to oxidative stress and consequent haemolysis.