Clinical Laboratory - Transfusion Medicine


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Massive Transfusion

Major blood loss is defined as the loss of one blood volume within a 24 hour period, a 50% loss in less than 3 hours for acute scenarios, or a rate of loss of 150 ml/min. Acute anemia from major blood loss may indicate the need for massive transfusion (MT). Massive transfusion is the lifesaving treatment of hemorrhagic shock that requires the transfusion of one blood volume. Major complications that may arise in patients who require massive transfusion include:

  • Hypothermia

  • Coagulopathy

  • Electrolyte abnormalities and Metabolic derangements, such as acidosis and alkalosis

Hypothermia

Hypothermia in patients with MT occurs as a result of

  • Exposure

  • Infusion of cold fluids and blood products

  • Opening of body cavities

  • Decreased heat production

  • Impaired thermoregulatory control

Hypothermia may lead to decreased metabolic,drug and hepatic metabolism with diminished immune responses and clot formation.

Hypothermia may be avoided by elevating the room temperature, warming the patient with heating blankets and the use of blood warmers during infusion.

Coagulopathy

Hemostatic abnormalities may arise in patients requiring MT due to a combination of dilution, consumption of clotting factors and fibrinolysis.

Coupled with hypothermia, impaired clot formation may further exacerbate blood loss. Coagulation is monitored with laboratory testing of the PT, PTT, and INR.

Coagulopathy may be avoided by transfusing PRBC:FFP:platelets in a 1:1:1 ratio or the use of recombinant factor VIIa as indicated.

Electrolyte Abnormalities

Serum potassium, calcium and magnesium may be disregulated with MT. As a result, cardiac arrest due to hyperkalemia; tetany, decreased myocardial contractility and hypotension due to hypocalcemia; and prolonged QT interval with hypomagnesemia are potential serious complications.

It is critical that the healthcare provider closely monitor Potassium, Calcium and Magnesium levels before and after transfusion, and corrections must be done as indicated.

Alkalosis and Acidosis

Blood is typically stored in citrate phosphate dextrose adenine (CPAD) solutions with a pH of 7.0 for most fresh PRBC units. As blood ages, citrate is metabolized to bicarbonate, and in patients who require MT, metabolic alkalosis may occur.

Metabolic acidosis arises a result of the hypoperfusion of tissues and is not directly related to blood product administration. The acidosis may be temporarily managed with the use of alkalinizing agents such as sodium bicarbonate or tromethamine, such as the case of patients with metabolic acidosis due to renal dysfunction or impairment. In acute patients, however, aggressive resuscitative efforts should be continued as the restoration of adequate tissue perfusion is paramount to the reversal of the underlying acidosis.

Complications from acidosis include coagulopathy and impaired hemostasis due to the inhibition of clotting factors and clot formation.


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