Acute haemodynamic effect of sodium bicarbonate in canine respiratory or metabolic acidosis.

This study has examined the acute haemodynamic effects of 7% sodium bicarbonate solution 1 mmol kg-1 (1.2 ml kg-1) administered into the right atrium over 5 s in 25 anaesthetized dogs allocated randomly to respiratory (arterial pH (pHa) 7.18, PaCO2 10.1 kPa (n = 8)) or metabolic acidosis (pHa 7.27, base deficit -9.0 mmol litre-1 (n = 7)) or metabolic neutrality (pHa 7.39 (n = 10)). The pHa and PaCO2 in the respiratory acidosis group differed from those in the two other groups (P < 0.01). One dog with respiratory acidosis developed progressive circulatory depression and cardiac arrest 6 min after injection of sodium bicarbonate. In the remaining seven dogs with respiratory acidosis, administration of sodium bicarbonate 1 mmol kg-1 produced transient decreases in mean arterial pressure, right ventricular dP/dt, and pulmonary blood flow, with increased right atrial pressure, followed by a gradual return of these variables to the baseline. The magnitude of reduction in pulmonary blood flow after sodium bicarbonate was greater in dogs with respiratory acidosis (P < 0.05) compared with the changes in the two other groups. The haemodynamic depression after bicarbonate was pronounced during respiratory acidosis and this may be attributed to a smaller pHa in the respiratory acidosis group, further reduction of intracellular pH, or both. It is suggested that when metabolic acidosis is corrected, bicarbonate should be administered with caution in the presence of respiratory acidosis.