Blood loss is a fact of life when surgery is done on any body part. Total knee replacements require cutting into the bone and that’s a major cause of blood loss. In an effort to reduce this problem, surgeons are studying what patient factors might be contributing to the bleeding. Is it the patient’s age? The way the tourniquet is applied to the leg? The patient’s sex (male versus female)?
Blood loss is measured by collecting fluid lost during and after the procedure. During the knee operation, a special suction unit (much like your dentist uses to remove fluid from your mouth) is used to collect blood lost. After surgery, special tubes called drains remain in the joint and transport fluid out of the joint.
Measuring blood loss isn’t exactly easy. The drains can’t collect all blood lost during this time. Fluid loss (including blood) is measured and a special formula applied to figure out how much was blood. At the same time, patients blood is tested for hematocrit and hemoglobin levels.
These two measures are another indication of how much blood has been lost. When the hemoglobin levels drop down too far, then a blood transfusion is ordered. Having patients donate their own blood before the operation for use during or afterwards is ideal. But sometimes (for various reasons) that isn’t possible, so family members are called upon to help out. Your blood may not be used if it’s not a match, but it will go into the blood bank to replenish the unit(s) donated by others that are used instead.