Does the administration of carbicarb lead acutely to back-titration of non-bicarbonate buffers?

OBJECTIVE

We have recently demonstrated in a model of acute metabolic acidosis in rats that the administration of NaHCO3 does not lead acutely to back-titration of non-bicarbonate buffers. Carbicarb is a new alkalinizing agent that has been proposed as a replacement for NaHCO3 in the treatment of metabolic acidosis. Hence, the purpose of this study was to examine the impact of carbicarb on back-titration of non-bicarbonate buffers.

METHODS

Rats were anaesthetized, intubated and ventilated to a PCO2 of approximately 30 mmHg. Acute metabolic acidosis was induced by the infusion over 1 hour of 3.5 mmol of hydrochloric acid. After a 20 min equilibration period, 3 groups of rats (n = 7 in each group) were examined. Rats in groups I received 0.75 meq of Na from 1 M carbicarb solution as an intravenous bolus, rats in group II received equimolar NaCl, while rats in group III were used as time controls. Calculations were performed to quantitate the amount of HCO3- that was retained in the ECF volume and the amount that was titrated with H+ and excreted as "acid-base" CO2. "Acid-base" CO2 was considered as the amount of CO2 that was excreted in excess of what would be produced during metabolism.

RESULTS

As compared to the NaCl and the time control groups, the administration of carbicarb led to significant alkalinization of the ECF, pH rose from 7.23 +/- 0.02 to 7.34 +/- 0.03. Of the 0.75 mmol of carbicarb that was administered, 0.61 +/- 0.05 mmol (70%) was retained in ECF. There was virtually no "acid-base" CO2 produced.

CONCLUSIONS

The administration of carbicarb does not lead acutely to back-titration of non-bicarbonate buffers especially under conditions of fixed ventilation.