Sodium modelling and profiled ultrafiltration in conventional haemodialysis

Summary: Previous controlled studies have shown that sodium modelling may reduce intradialytic hypotension and symptoms (particularly cramp, headache and nausea) in patients on maintenance haemodialysis, and it has been proposed that decremental profiled ultrafiltration may improve haemodynamic stability. Those controlled studies of sodium modelling were flawed because sodium modelling programmes were compared to a constant sodium dialysate concentration lower than the overall mean sodium concentration during sodium modelling (the ‘true mean’). to compare sodium modelling to its true mean constant dialysate concentration and also to compare profiled ultrafiltration with constant ultrafiltration, 12 patients on conventional haemodialysis were dialysed by four regimens in random order each for 3 weeks: (i) sodium modelling (exponential decline from 150 to 140 mmol/L) and conventional (linear) ultrafiltration; (ii) sodium modelling and profiled (65% of target loss in first 2 h) ultrafiltration; (iii) constant sodium (143 mmol/L, the true mean) and conventional ultrafiltration; and (iv) constant sodium and profiled ultrafiltration. Weight gain and pre-dialysis blood pressure were no different between the four regimens. Sodium modelling had no effect on the frequency of intradialytic hypotension or need for saline administration when compared to a constant sodium dialysate of 143 mmol/L, nor improved frequency or severity of thirst, cramp, nausea and lethargy. Interdialytic headache was less severe (P<0.05) but no less frequent with sodium modelling. Profiled ultrafiltration increased the frequency of intradialytic hypotension (odds ratio 2.44, P<0.05) and did not improve symptoms except interdialytic thirst, which occurred less frequently than with linear ultrafiltration (odds ratio 0.55, P<0.05). the haemodynamics and symptoms were no better with sodium modelling and profiled ultrafiltration than with constant sodium dialysis and linear ultrafiltration, respectively. Thus, there is no justification for the routine use of sodium modelling or profiled ultrafiltration in conventional haemodialysis on the grounds of haemodynamic stability or symptom control.