Effects on ionized calcium of a correction of acidosis with alkalinizing agents. A rational basis for the administration of calcium in cardiac resuscitation.

The effects on the ionized calcium concentration of a correction of various forms of acidosis with sodium bicarbonate or (tris-hydroxymethyl)aminomethane (THAM) were investigated in vitro in human plasma. Calculation of least square regression equations of ionized calcium (m mol) on pH yielded the following regression coefficients: hydrochloric acidosis: -0.65 +/- 0.06; lactic acidosis: -0.27 +/- 0.05; hydrochloric acidosis corrected with sodium bicarbonate: -0.65 +/- 0.02; lactic acidosis corrected with sodium bicarbonate: -0.51 +/- 0.03. The results indicate that after correction of lactic acidosis the ionized calcium concentration will be below the control values while pH is restored to the normal range. This effect is even more pronounced when THAM is used. The findings point to the need for calcium administration in cardiac resuscitation.