Does bicarbonate transfer have relevant hemodynamic consequences in standard hemodialysis?

Area of Science:

• Nephrology
• Cardiovascular Physiology
• Dialysis Technology

Background:

• Previous research indicated that standard bicarbonate hemodialysis can cause hypotension due to metabolic alkalosis.
• This study investigated hemodynamic effects of altering dialysate bicarbonate and calcium concentrations.
• The research aimed to determine if calcium shifts secondary to alkalemia contribute to blood pressure changes during dialysis.

Purpose of the Study:

• To compare the hemodynamic consequences of decreasing dialysate bicarbonate versus increasing dialysate calcium.
• To verify if calcium shifts related to alkalemia explain blood pressure changes during hemodialysis.
• To assess the impact of different dialysate compositions on blood pressure, heart rate, and hypotension incidence.

Main Methods:

• A randomized controlled trial with a single-blind, cross-over design was employed.
• Dialysis solutions with varying bicarbonate (26 vs. 32 mmol/l) and calcium (1.25 vs. 1.50 mmol/l) concentrations were used.
• Hemodynamic parameters including blood pressure, heart rate, and hypotension incidence were monitored in 27 patients over 243 dialysis sessions.

Main Results:

• No significant differences in hemodynamic parameters were observed between standard bicarbonate (32 mmol/l) and reduced bicarbonate (26 mmol/l) dialysis.
• Increasing dialysate calcium (1.50 mmol/l) led to increased systolic and diastolic blood pressures and a reduced incidence of hypotension (1.2% vs. 10.5%).
• A subgroup of patients with lower blood pressure on higher bicarbonate dialysis showed less pronounced pressure increases with higher calcium, but no significant difference in hypotension incidence compared to standard bicarbonate.

Conclusions:

• The study did not demonstrate hemodynamic instability associated with mild metabolic alkalosis during hemodialysis.
• Even in patients prone to lower blood pressure with higher dialysate bicarbonate, no significant clinical consequences were observed.
• The calculated calcium shift due to alkalemia suggests a minimal impact (approx. 1 mm Hg) on systolic blood pressure.