Electrolyte Mass Balance During CVVH: Lactate vs. Bicarbonate‐Buffered Replacement Fluids

Abstract

Objective: To compare the effect of lactate vs. bicarbonate‐buffered replacement fluids on electrolyte mass balance during isovolemic continuous veno‐venous hemofiltration (CVVH). Design: Randomized controlled study with double cross over. Setting: Intensive care unit of a tertiary university hospital. Patients and participants: Eight patients with acute renal failure (ARF). Interventions: Isovolemic CVVH (2L/hr of replacement fluid) was performed in random order with either bicarbonate or lactate‐buffered replacement fluid delivered pre‐filter. Measurements and Results: Sodium, potassium, chloride, magnesium, and phosphate, were measured in each sample. There was a mass gain of sodium, which was similar under both conditions (bicarbonate: 23.3 ± 4.9 mmol/hr, lactate: 22.7 ± 3.5 mmol/hr). Mass chloride gains occurred with bicarbonate‐buffered replacement fluid only (12.8 ± 5.3 mmol/hr), while there was an overall net loss of chloride with lactate fluids (− 2.5 ± 5.2 mmol/hr), resulting in a significant difference in chloride mass balance (p < 0.0001). Magnesium mass balance was negative with bicarbonate buffer only (− 0.6 ± 0.2 mmol/hr) and also differed significantly from that obtained with lactate fluids (− 0.1 ± 0.2 mmol/hr, p < 0.0001). Phosphate losses (bicarbonate: − 1.7 ± 0.7 mmol/hr, lactate: − 1.7 ± 0.5 mmol/hr) were equivalent with both buffers. Potassium mass balance was neutral. Conclusions: Mass balance during isovolemic CVVH is significantly affected by the type of replacement fluid administered pre‐filter. Isovolemic CVVH is not isonatremic and the use of bicarbonate‐buffered fluid results in a significant accumulation of chloride and a loss of magnesium.

• Hemofiltration
• Septic shock
• Acute renal failure
• Electrolyte
• Sieving coefficient