Tolerance of haemodialysis: a randomized cross-over trial of 5-h versus 4-h treatment time.

BACKGROUND Many factors can impair haemodialysis (HD) tolerance. Some such as age and diabetes mellitus are linked to the patient. Others, such as dialysate, machine, and membrane are linked to the treatment characteristics. The duration of the HD sessions may represent another factor in tolerance since it influences the rate of ultrafiltration. However, its influence has not been studied independently of the type of membrane or dialysate buffer. METHODS In a randomized crossover study, the incidence of intradialytic symptoms was compared during 4-h and 5-h HD sessions in 38 patients. The study period was 2 weeks for each dialysis time. The influence of age and diabetes was also analysed. Sessions requiring more than 4 litres of ultrafiltration were excluded. RESULTS During the 5-h period, the incidence of headache, nausea, chills, back pain and pruritus was significantly greater. On the contrary, the incidence of hypotension and postdialytic orthostatic hypotension was significantly less. We also demonstrated that ultrafiltration rate and orthostatic hypotension were correlated, and that age over 65 years and diabetes influenced HD tolerance. The incidence of hypotension was significantly less in patients over 65 receiving 5-h HD treatment. CONCLUSIONS Although some symptoms were more frequent during the 5-h HD sessions, the incidence of hypotension and postdialytic orthostatic hypotension was significantly less. This resulted in an improvement in acute haemodynamic HD tolerance, which could also influence long-term morbidity and mortality, especially in patients over 65 years.