Postoperative blood loss into plaster casts after clubfoot surgery: an experimental model.

With major surgery in mind, a simple experimental model was used to study the potential blood loss into plaster of Paris casts. Three lower limb models were used to represent a 3-year-old, a 1-year-old, and a 6-month-old. Two thicknesses of plaster were compared in terms of blood volume required to produce staining on the surface of the cast. Whole blood from the laboratory was infused onto the plaster models at various rates. While allowing for the limitations of the model, the blood volume required before staining through the plaster when three plaster rolls were used was an average of 160 mL in the 6-month-old model and 310 mL in the 3-year-old modal, representing 31.4% and 29.5% of total blood volume, respectively. When only two rolls of plaster of Paris were used, an average of 80 mL in the 6-month-old and 180 mL in the 3-year-old model were lost, representing 15.7% and 17% of total blood volume, respectively. This potential blood loss should be borne in mind during major pediatric foot surgery. The use of drains, releasing the tourniquet before wound closure, and casting with two rather than three rolls of plaster are suggested precautions.