A transfusion supplies whole blood or one of its components through an intravenous line to an ill or injured patient. In most cases, transfusing one unit of blood---about one pint---takes about four hours. Life-threatening hemorrhage from traumatic injuries, however, may require massive transfusion, defined as replacing an amount equal to or greater than the patient's total blood volume within a 24 hour period, according to the Merck Manual. Rapid infusion of stored blood may cause complications.
Impaired Clotting
Dilutional thrombocytopenia, the most common cause of bleeding after a massive transfusion, results from the properties of stored donor blood, according to anesthesiologist Paul H. Ting, M.D., in a 2002 article published on his website, "Anesthesiology Info." Massive transfusion essentially replaces the patient's own blood, leaving only about one third of the blood's original components, according to the Merck Manual. Since the platelets---the cell fragments required for clotting---in stored donor blood have lost their function, the patient may begin to bleed or ooze from cuts and wounds because the new blood does not clot properly.
Citrate Toxicity and Low Calcium
The liver metabolizes 3g of citrate every five minutes, the same amount contained in each unit of stored donor blood. Patients with liver disease or who receive rapid transfusions, faster than one unit every five minutes, may develop citrate toxicity, a condition that binds the calcium in the patient's body and produces low blood pressure and tetany, according to Ting. Intravenous calcium assists in treating symptomatic hypocalcemia.
Hypothermia
Rapidly transfusing large amounts of refrigerated donor blood may cause irregular heartbeats or cardiac arrest, according to the Merck Manual. Hypothermia may also cause problems with clotting. Raising the blood and other fluids to room temperature helps to avoid hypothermia.
Potassium Imbalance
Although the potassium level in blood increases during storage, hyperkalemia---high potassium level, poses little risk to the recipients except in cases of massive transfusions or kidney disease, according to the Merck Manual. As the patient begins to recover, the patient may actually become hypokalemic and require potassium supplementation.
General Transfusion Complications
Regardless of the rate of transfusion, donor blood may transmit infections caused by bacteria, viruses and parasites, including malaria, HIV, syphilis, West Nile virus, hepatitis B and C, and other diseases, according to the Merck Manual. Other possible complications include a potentially fatal hemolytic reaction when the the blood types of the donor and patient do not match; allergic reactions; acute lung injuries; or heart failure from infusing too much fluid. Iron overload, a potential result of multiple infusions, can damage the heart, liver and other organs as well.
