Insufficient correction of blood bicarbonate levels in biguanide lactic acidosis treated with CVVH and bicarbonate replacement fluids

Background: In the course of Continuous Veno-Venous Hemofiltration (CVVH), bicarbonate buffer instead of lactate is suitable for the treatment of combined renal and hepatic failure and for patients suffering from lactic acidosis, type A or B, joined with acute renal failure (ARF).

Methods: We applied the CVVH buffered with bicarbonate for the treatment of two patients affected by ARF and severe lactic acidosis type B (due to biguanide intoxication) and we evaluated its ability to correct the acid-base balance.

Results: Clinical and laboratory data show that this technique, performed in standard conditions (plasma flow: 70 ml/min, ultrafiltration: 25 ml/min, bicarbonate concentration in the infusion fluid: 30 mEq/L), was inadequate to compensate for the high requirement of bicarbonate (approximately 280 mEq/hr during the first 6 hours of observation) and the severe metabolic acidosis, thus additional bicarbonate infusion was needed.

Conclusions: In particular, from ascertained data and theoretical considerations, in the course of lactic acidosis caused by biguanide, in order to correct acidosis a positive balance of bicarbonate could be obtained only by means of a bicarbonate-based replacement fluid and of a continuous high flow hemofiltration, such as to assure an ultrafiltrate volume exceeding 150 ml/min.