#1328 Haemodynamic effects of low versus high dialysate bicarbonate concentration in haemodialysis patients

Abstract

Abstract Background and Aims Haemodialysis (HD) treatment using standard dialysate bicarbonate concentrations cause transient metabolic alkalosis possibly associated with haemodynamic instability. We performed a detailed comparison of blood pressure (BP), haemodynamic parameters, electrolytes and orthostatic BP response with low (LDB) versus high dialysate bicarbonate concentration (HDB). Method Fifteen HD patients were examined in a single-blind, randomised, controlled, crossover study. Participants underwent a 4-hour HD session with dialysate bicarbonate concentration of 30 mmol/l (LDB) or 38 mmol/l (HDB) with one week between interventions. During HD, cardiac output (CO), total peripheral resistance (TPR), stroke volume (SV) and central blood volume were measured with ultrasound dilution technique (Transonic). Throughout dialysis, blood samples were obtained from the arterial cannula. Orthostatic BP was measured pre and post HD. Results With similar ultrafiltration volume (2.6 litres), systolic BP tended to decrease more during HDB compared to LDB (Fig. 1 and Table 1); the mean (95% confidence interval) between treatment differences in systolic BP were: 8 (-4;20) mmHg (end of HD) and 7 (0;15) mmHg (post HD). SV decreased (Fig. 2) whereas TPR increased significantly more during HDB compared to LDB with mean between treatment differences: SV: 12 (1;23) ml; TPR: -2.9 (-5.3;-0.5) mmHg/(L/min). CO tended to decrease more with HDB compared to LDB with mean between treatment difference 0.7 (0.0;1.4) L/min. HDB caused alkalosis, hypocalcaemia and lower plasma potassium, whereas patients remained normocalcaemic with normal pH during LDB (Table 1). Orthostatic BP response after dialysis did not differ significantly. Conclusion HDB compared to LDB was associated with hypocalcaemia and alkalosis and a more pronounced hypokalaemia which may impair preservation of BP, SV and CO during HD.