 After the blood collection process, "in vitro" hemolysis can still occur in a sample due to external factors, such as prolonged storage, incorrect storage conditions and excessive physical forces by dropping or vigorously mixing the tube.In some surgical procedures (especially some heart operations) where substantial blood loss is expected, machinery is used for intraoperative blood salvage.A centrifuge process takes blood from the patient, washes the red blood cells with normal saline, and returns them to the patient's blood circulation.