Under what condition should calcium be administered?

Administering calcium is particularly important after the first unit of blood is transfused because blood products can cause a dilutional effect that may lead to hypocalcemia. When large volumes of citrated blood are transfused, the citrate used as an anticoagulant can bind calcium in the bloodstream, potentially resulting in low calcium levels. This can lead to complications such as cardiac dysfunction, especially in cases of rapid or massive transfusions.

By administering calcium after the initial unit, you can mitigate these risks and ensure that the patient maintains adequate calcium levels, thus preventing potential complications associated with hypocalcemia. This practice helps ensure optimal cardiovascular function and reduces the likelihood of arrhythmias during blood transfusion procedures where the risk of citrate-induced hypocalcemia is a concern.

The timing of calcium administration is critical, as it should not be given for every blood transfusion or as a general preventive measure before all transfusions, which may not be warranted in every case. Each unit of blood does not always cause a significant drop in calcium levels, so assessing the situation based on volume and rate of transfusion is essential.