Massive transfusion is traditionally defined as transfusion of 10 units of packed red blood cells (PRBCs) within a 24 hour period. Massive transfusion protocols (MTPs) are established to provide rapid blood replacement in a setting of severe hemorrhage. Early optimal blood transfusion is essential to sustain organ perfusion and oxygenation. The goal of massive transfusion is to limit complications and to limit critical hypoperfusion while surgical hemostasis can be achieved. Patients potentially requiring massive transfusions can be seen across medicine from traumatic injuries, gastrointestinal bleeding, and obstetric catastrophes. While surgery is the most common use of major transfusion protocols (MTPs), trauma remains the best-studied category in massive transfusion. Massive transfusion requires the consideration of multiple physiologic parameters such as volume status, tissue oxygenation, management of bleeding and coagulation abnormalities, and acid-base base balance.
Volume Status and Tissue Oxygenation
The focus when a patient is in hypovolemic shock secondary to acute blood loss is to expand intravascular volume and maintain oxygen delivery to tissues. At baseline, oxygen is delivered to tissues at approximately four times the rate of oxygen tissue consumption. Therefore, volume expanders such as crystalloids may be employed during a massive transfusion to maintain blood pressure and tissue perfusion. However, if a patient is in severe shock, or if they continue bleeding, blood will eventually be required to maintain oxygen delivery at an appropriate rate.
Patients requiring a massive transfusion are often acidotic even before transfusion begins. Prolonged states of hypoperfusion lead to acidosis. Once acidosis has set in, it further interferes with coagulation by reducing the assembly of coagulation factors. There is a direct relationship between decreasing pH (increasing acidosis) and reduction in the activity of coagulation cascade components. This results in delayed and thin fibrin clot formation, which is more quickly destroyed through fibrinolysis.
Many patients with acute, blood-loss anemia are also susceptible to hypothermia, which again can lead to coagulopathy. Lower ambient temperatures and decreased blood volume can predispose these patients to hypothermia. Hypothermia reduces the efficacy of both the coagulation cascade (by reducing the enzymatic activity of coagulation proteins) and platelet plug formation. At 34 C, effects on coagulation begin, and at 30 C, there is approximately a 50% reduction in platelet activation.
Coagulopathy and Dysfunctional Hemostasis
Due to massive bleeding, coagulation factors are often being consumed in patients who may require massive transfusion. Additionally, dilution of the remaining coagulation components due to volume expanders in addition to hypothermia and acidosis can lead to coagulopathy and altered hemostasis. The decreased ability to stop bleeding leads to further hypothermia and acidosis, creating a positive feedback loop that results in worsened patient outcomes.
Indications For massive transfusion:
The primary indication for massive transfusion is any situation resulting in acute blood loss and hemodynamic instability. Indications for massive transfusion include, but are not limited to, bleeding due to trauma, obstetrical catastrophes, surgery, and gastrointestinal bleeding.
Targets of resuscitation in the setting of massive transfusion include:
- Mean arterial pressure (MAP) of 60 to 65 mm Hg
- Hemoglobin 7 to 9 g/dL
- INR less than 5
- Fibrinogen greater than 1.5 to 2 g/L
- Platelets greater than 50 times 10/L
- pH 7.35 to 45
- Core temperature greater than 35 C
Potential complications of massive transfusion include metabolic alkalosis, hypocalcemia, hypothermia, and hyperkalemia. Non-fatal complications have been seen in more than 50% of patients when more than 5 units of blood products are transfused.
Metabolic alkalosis and hypocalcemia result from sodium citrate and citric acid that is added to blood products in storage to prevent coagulation. Each unit of blood can generate a total of 23 mEq of bicarbonate as citrate is metabolized. This can result in a metabolic alkalosis if the kidneys are unable to excrete the excess bicarbonate. Additionally, the alkalosis can result in hypokalemia as hydrogen ions move out of cells to compensate for the alkalosis through an H+/K+ transporter. Citrate also binds ionized calcium, which can lead to significant free hypocalcemia. It typically does not affect calcium bound to albumin. Severe hypocalcemia can result in paresthesias and cardiac dysrhythmias. Hypothermia can also result from the infusion of blood products. Blood products are stored at 4 C. Rapid infusion of cold blood can lead to lower core body temperatures. Given that this population is already predisposed to hypothermia, which can further worsen coagulopathy, many rapid infusers also have warmers to reduce the risk of hypothermia during massive transfusion. Hyperkalemia is also a possible complication as potassium can increase in blood during long-term storage. It is typically only seen when blood products have been stored for long periods and are infused through central access at high speeds.
Massive transfusion is an important life-saving intervention for patients with massive acute blood loss. Massive transfusion has been used in many clinical settings including obstetrics, gastroenterology, trauma, and the operating room. Although the etiology of bleeding is different in all of the cases, the same principles of massive transfusion apply. Massive transfusion can, however, have serious complications and should be reserved for patients with hemodynamic instability as a bridge to definitive therapy.
What’s in the Massive Transfusion Protocol (MTP) Package? The Massive Transfusion Protocol Package is a set of documents intended to improve the coordination of a Massive Transfusion Protocol. The kit contains:
- A checklist to help improve Massive Transfusion Protocol process
- Tips and reminders of important points for Massive Transfusion Protocol
- Massive Transfusion Protocol
- A sign to alert others that a computer is dedicated to
- Blood Product Tracking
- Issue Voucher for Blood Products (if labels unavailable)
- Request form for Factor
Massive transfusion, historically defined as the replacement by transfusion of 10 units of red cells in 24 hours, is a response to massive and uncontrolled hemorrhage. With more rapid and effective therapy, alternative definitions such as three units of red blood cells over one hour or any four blood components in 30 minutes are more sensitive in identifying patients needing rapid issue of blood products for serious injuries because of uncontrolled hemorrhage. Such transfusion episodes are associated with a number of hemostatic and metabolic complications. Massive transfusion involves the selection of the appropriate amounts and types of blood components to be administered, and requires consideration of a number of issues including volume status, tissue oxygenation, management of bleeding and coagulation abnormalities, as well as changes in ionized calcium, potassium, and acid-base balance.
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