Ionized Calcium En Aodosis: Differential Effect of Hypercapnic and Lactic Acedosis

The effects of various forms of acidosis on ionized calcium concentrations were investigated in vivo in rabbits and in vitro in human plasma. Calculation of least square regression equations of ionized calcium (mM) on pH yielded the following regression coefficients in human plasma: bypercapnic acidosis —0.53±0.07; hydrochloric acidosis —0.65 ±0.06; lactic acidosis —0.27±0.05. These findings in human plasma are roughly paralleled by those in rabbits. From stability constants it was calculated that the formation of Ca-lactate complexes accounts for the difference between lactic and hydrochloric acidosis. It is concluded that differences in the behaviour of ionized calcium between hypercapnic and lactic acidosis might contribute to the known differences in cardiovascular effects.