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Ventricular pump performance during hypocalcemia: clinical and experimental studies
Insights
Rapid blood transfusion with citrate lowers calcium, potentially impairing heart function. Heparinized blood, however, improves cardiac output and ventricular function without affecting calcium levels.
Area of Science:
- Cardiology
- Physiology
- Transfusion Medicine
Background:
- Rapid blood transfusions are common in cardiac surgery.
- Citrate, an anticoagulant, can chelate calcium, potentially affecting cardiac function.
- Understanding the impact of different anticoagulants on ventricular function is crucial.
Purpose of the Study:
- To compare the effects of rapid autologous blood transfusion using citrated versus heparinized blood on ventricular function.
- To investigate the role of ionized calcium levels in mediating these effects.
Main Methods:
- Six patients undergoing cardiopulmonary bypass received rapid infusions of either citrated or heparinized autologous blood.
- Measurements included plasma ionized calcium concentration, pulmonary artery occlusion pressure, and left ventricular performance indices (stroke work index, stroke index, cardiac index).
- A canine model was used to further assess ventricular function under hypocalcemia and beta-blockade.
Main Results:
- Citrated blood transfusion led to a significant decrease in plasma ionized calcium and an increase in pulmonary artery occlusion pressure, without altering left ventricular performance indices.
- Heparinized blood transfusion did not affect plasma ionized calcium but increased pulmonary artery occlusion pressure and improved left ventricular stroke work index, stroke index, and cardiac index.
- In dogs, severe hypocalcemia shifted ventricular function curves downward and to the right, indicating impaired function.
- Combined hypocalcemia and beta-blockade resulted in severe left ventricular failure.
Conclusions:
- Rapid transfusion of citrated blood may transiently impair ventricular function due to hypocalcemia.
- Heparinized blood transfusion appears to be better tolerated, potentially improving cardiac performance.
- Hypocalcemia significantly depresses left ventricular function, an effect exacerbated by beta-blockade.
Abstract:
We have compared indices of ventricular function during rapid transfusion of citrated (1.5 ml/kg/min) or heparinized (1.5 ml/kg/min) autologous blood in six patients following discontinuation of cardiopulmonary bypass. Infusion of citrated blood was associated with a lowering of plasma ionized calcium concentration ([Ca++], from 0.90 +/- 0.04 to 0.71 +/- 0.4 mM, p less than 0.001) and an increase in pulmonary artery balloon-occluded pressure (PA0, from 9.4 +/- 2.6 to 15.5 +/- 1.7 mm Hg, p less than 0.u1), without a change in left ventricular stroke work index, stroke index, or cardiac index. Transfusion of heparinized blood caused no change in plasma [Ca++]. A rise in PA0, which was similar in magnitude to that observed during citrated blood transfusion, was associated with increased left ventricular stroke work index, stroke index, cardiac index, and mean arterial pressure. Although data obtained during citrated blood transfusion suggest the presence of transient left ventricular dysfunction, its magnitude is not readily expressed in terms of ventricular function curves when accompanied by a simultaneous change in [Cized closed-chest dog by volume loading during hypocalcemia, when mean arterial pressure, heart rate, and [Ca++] were in a steady state, both prior to and following beta blockade with propranolol. Function curves obtained during severe hypocalcemia ([Ca++] = 0.43 +/- 0.02 mM) were shifted significantly to the right and downward, when compared to those obtained during normocalcemia ([Ca++] = 1.06 +/- 0.03 mM). Hypocalcemia combined with beta blockade resulted in severe left ventricular failure, as demonstrated by a flat ventricular function curve.