Relationship between cardiovascular functions and ionic hypocalcemia induced by citrate infusion in anhepatic swines:...

Baseline and serial values of serum [Ca++], [K+], [Na+], arterial blood gas tensions, acid-base status, temperature and hemodynamic functions were measured during infusion of citrate-phosphate-dextrose (CPD) solution (0.35 ml.kg-1 x min-1) in anhepatic pigs of three randomized groups. Thirteen pigs (group I) continued to receive intravenous infusion of CPD solution until cardiac arrest. When mean arterial pressure (MAP) decreased to about 50 mmHg (group II, n = 7), or 40 mmHg (group III, n = 7) infusion of CPD solution was discontinued, and pigs received CaCl2 (20 mg/kg) intravenously. Serial (1, 4, 8, and 12 min after CaCl2 administration) values of all the above variables and serum citrate at baseline and lowest [Ca++] were measured. After hepatectomy and venovenous bypass, cardiac output (CO) decreased 30%. When ionic hypocalcemia was above 0.7 mM, there was no significant change of cardiovascular functions. When [Ca++] was between 0.34-0.7 mM, there were linear relationships between [Ca++] and CO, systemic vascular resistance (SVR) and MAP, respectively. When [Ca++] was below 0.34 mM, cardiovascular functions decreased abruptly, and the pigs died at [Ca++] of 0.26 +/- 0.06 mM. When [Ca++] decreased to 0.36 +/- 0.06 mM and MAP to 50 +/- 4 mmHg, most hemodynamic functions could be reversed by calcium therapy. However, when [Ca++] decreased to 0.33 +/- 0.05 mM and MAP to 40 +/- 2 mmHg, hemodynamic functions could not be reversed by calcium therapy alone.