The most frequent indication for massive blood transfusion is hypovolemic shock secondary to blood loss (hemorrhagic shock), most often seen in the setting of trauma, ruptured aortic aneurysm, massive GI hemorrhage and liver transplantation.

The initial resuscitation in hemorrhagic shock should begin with crystalloid infusion to restore intravascular volume followed by infusion of red cells to restore adequate oxygen delivery to tissues. Isotonic salt solutions (normal saline or Ringer’s lactate) are the most common crystalloid solutions used. Colloid solutions (pentastarch or albumin) should be limited to a secondary agent for fluid resuscitation. Normal saline is the only salt solution that may be mixed directly with blood components. It is important to keep in mind that, most frequently, in the massive transfusion setting, primary surgical treatment is required to achieve hemostasis. The transfusion of blood components is usually a supportive, rather than primary therapeutic intervention for hemostasis.

Regardless of the emergency, the patient’s identity should be checked against the patient compatibility tag attached to the blood bag to be infused. All blood products must be transfused through a standard blood infusion filter. Massive blood transfusion metabolic effects are not unpredictable. Therefore, baseline laboratories, including hematocrit/ hemoglobin, platelet count, prothrombin time, partial thromboplastin time, fibrinogen, arterial blood gases, electrolytes and electrocardiogram should be performed. Follow-up laboratories should be repeated as clinically indicated, prior to correction of symptoms.

Metabolic Derangements: The patient’s underlying condition and rate of blood administration will have the greatest effect on the developments of the most commonly observed derangements: hypothermia, coagulation abnormalities, citrate toxicity, and hyperkalemia.

Hypothermia: Hypothermia is often present, mostly as a consequence of shock due to loss of thermal regulation but compounded by intravascular infusion of cold fluids and a cold environment. Warming of crystalloid solutions may be supplemented with blood warming when blood is rapidly infused through a central line and/or when infusion rate is faster than 50 ml/kg/hour (60 mL/min in an adult). Acidosis and coagulopathy are most likely to develop secondary to hypoperfusion and hypothermia and not to the massive blood replacement.

Citrate Toxicity: By chelating calcium, citrate prevents clotting in blood products during storage. During massive transfusion, the dose of citrate infused is influenced primarily by the type of blood component and by the rate of administration. The infused citrate is rapidly metabolized and excreted by the liver and kidneys, respectively with bicarbonate being the end product. Citrate toxicity can be manifested by hypocalcemia, neuromuscular or cardiac abnormalities. Laboratory evaluations for acid-base status and ionized calcium are strongly recommended prior to initiation of pharmacological therapy, as calcium overtreatment is associated with significant morbidity or mortality.

Packed Red Blood Cells: Red cell transfusions initially may be achieved with uncrossmatched type O red cells. By limiting the use of O negative red cells to children and women of child bearing age, a valuable and scarce resource will be preserved. If a patient’s blood type has been determined, ABO and Rh specific red cells can be used. Every effort should be made to establish the blood type of a patient prior to transfusion to preserve type O red cell availability and accurately determine the patient’s blood type.

Platelets: Platelet transfusion therapy after massive transfusion is an accepted intervention in the presence of microvascular bleeding prior to documentation of thrombocytopenia. The platelet transfusion dose recommended is 1 unit per 10 kg body weight for platelet counts <50,000 or when platelet dysfunction is suspected.

Plasma: Plasma transfusion therapy should be instituted after laboratory confirmation of coagulation factor deficiencies. The recommended dose is 10-15 mL/kg body weight for PT/PTT>1.5 normal range.

Cryoprecipitate: Cryoprecipitate therapy should be instituted for the correction of laboratory evidence of hypofibrinogenemia (fibrinogen <100 mg/dL). Dosing will depend on the degree of hypofibrinogenemia and the patient’s weight. For an average size adult, 6-unit pool for fibrinogen levels between 50-100 mg/dL; 12-unit pool for fibrinogen levels <50 mg/dL.