Haemodynamic consequences of changing bicarbonate and calcium concentrations in haemodialysis fluids.
BACKGROUND
In a previous study we demonstrated that mild metabolic alkalosis resulting from standard bicarbonate haemodialysis induces hypotension. In this study, we have further investigated the changes in systemic haemodynamics induced by bicarbonate and calcium, using non-invasive procedures.


METHODS
In a randomized controlled trial with a single-blind, crossover design, we sequentially changed the dialysate bicarbonate and calcium concentrations (between 26 and 35 mmol/l for bicarbonate and either 1.25 or 1.50 mmol/l for calcium). Twenty-one patients were enrolled for a total of 756 dialysis sessions. Systemic haemodynamics was evaluated using pulse wave analysers. Bioimpedance and BNP were used to compare the fluid status pattern.


RESULTS
The haemodynamic parameters and the pre-dialysis BNP using either a high calcium or bicarbonate concentration were as follows: systolic blood pressure (+5.6 and -4.7 mmHg; P < 0.05 for both), stroke volume (+12.3 and +5.2 ml; P < 0.05 and ns), peripheral resistances (-190 and -171 dyne s cm(-5); P < 0.05 for both), central augmentation index (+1.1% and -2.9%; ns and P < 0.05) and BNP (-5 and -170 ng/l; ns and P < 0.05). The need of staff intervention was similar in all modalities.


CONCLUSIONS
Both high bicarbonate and calcium concentrations in the dialysate improve the haemodynamic pattern during dialysis. Bicarbonate reduces arterial stiffness and ameliorates the heart tolerance for volume overload in the interdialytic phase, whereas calcium directly increases stroke volume. The slight hypotensive effect of alkalaemia should motivate a probative reduction of bicarbonate concentration in dialysis fluid for haemodynamic reasons, only in the event of failure of classical tools to prevent intradialytic hypotension.
Division of Nephrology, Ospedale la Carità, Locarno, Switzerland. luca.gabutti@eoc.ch
Luca
L
Gabutti
Giorgia
G
Bianchi
Davide
D
Soldini
Claudio
C
Marone
Michel
M
Burnier
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001639:Bicarbonates / Q000008:administration & dosage*; D002021:Buffers; D002119:Calcium Carbonate / Q000008:administration & dosage*; D002908:Chronic Disease; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D015312:Hemodialysis Solutions / Q000737:chemistry*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007674:Kidney Diseases / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000379:methods*; D016037:Single-Blind Method
D001639:Bicarbonates; D002021:Buffers; D015312:Hemodialysis Solutions; D002119:Calcium Carbonate