Plasma Transfusion Guidelines

Today, much plasma is ordered prophylactically to correct an elevated protime (PT) prior to an invasive procedure. Physicians performing invasive procedures want to avoid hemorrhagic complications and often regard a mild elevation of a coagulation test result as an indication to order plasma.  The decision to prophylactically transfuse plasma is based on three unproven assumptions:  

1. Mild prolongation of PT/INR (defined as an INR <1.7) predicts  bleeding from an invasive  procedure
2. Pre-procedure transfusion of plasma will correct a prolonged PT/INR
3. Prophylactic plasma transfusions result in fewer bleeding events

The evidence clearly contradicts the first assumption. PT and APTT begin to rise above the upper limit of the normal range when coagulation factor levels fall below approximately 70% of normal.  When the INR increases to 1.3 - 1.5, vitamin K dependent coagulation factors are still 50% of normal. Even at an INR between 1.8 and 2.0, they remain at 30% of normal, which is still at or above the minimal hemostatic level of 20 -30%. These results explain why a mildly elevated PT/INR is not usually associated with spontaneous hemorrhage and does not increase the risk of bleeding during routine invasive procedures.  Studies during the last 20 years in patients undergoing liver biopsies, bronchoscopic biopsies, renal biopsies, central line vein cannulation, thoracentesis and angiography have repeatedly demonstrated that PT and activated plasma thromboplastin time (APTT) are not predictive of hemorrhage. However, it must be remembered that the risk of bleeding is greater if the platelet count is decreased, platelet function is abnormal, or the patient has experienced massive trauma or is undergoing extensive surgery.

Additional evidence clearly disputes assumptions 2 and 3. Prophylactic transfusion of plasma to correct a mildly elevated INR prior to an invasive procedure is often not effective. When the INR is <1.7, transfusion of plasma corrects INR an average of only 0.1 per unit transfused, largely because the INR of plasma itself ranges between 1.0 and 1.3. The difference in coagulation activity between donor plasma and patient plasma is so small that plasma transfusions produce minimal demonstrable effect on the patient’s INR.

INR Correction by FFP

While a patient with an INR of 1.7 or less may bleed during an invasive procedure, the medical literature clearly demonstrates that the incidence of hemorrhage is not different from that of patients with a normal INR.

In summary, plasma transfusion has minimal effect on normalizing the INR in patients with mildly prolonged INRs for the following reasons:  

1. Plasma produced from healthy blood donors can have an INR as high as 1.3
2. Plasma transfusion to a patient with an INR of less than 1.7 has minimal effect
3. Plasma transfusion to patients with an INR of less than 1.7 does not decrease the INR more than usual medical care without plasma transfusion

In view of this information, the common practice of prescribing plasma to correct a mildly elevated INR prior to an invasive procedure needs to be reevaluated. It is not necessary or efficacious to correct an INR below 1.7 to achieve adequate hemostasis.

For patients with highly prolonged INR secondary to excessive anticoagulation, the American College of Chest Physicians (ACCP) has published guidelines to facilitate warfarin reversal in patients with or without bleeding.

ACCP Warfarin Reversal Guidelines

For elective surgery, the best strategy for warfarin reversal is to discontinue warfarin 3 to 5 days prior to the procedure. Patients presenting with minor bleeding may be treated by withholding the next dose of warfarin and giving oral Vitamin K. When vitamin K replacement therapy is used, its effect does not begin until 6-12 hours after administration and is not complete until 36 hours. Patients with greatly elevated INR’s are at high risk for intracranial hemorrhage and should be given plasma concomitantly with vitamin K therapy.

Acquired abnormalities of hemostasis may occur with a variety of other clinical disorders. These usually involve multiple plasma coagulation factor deficits and are more common than inherited plasma deficiencies that usually involve single coagulation factor deficiencies. Consequently, there is a concurrent derangement of several coagulation tests as shown in following table.

Acquired Plasma Coagulopathies

The goal of plasma transfusion is to increase the plasma level of each coagulation factor above 30%. Each bag increases the level of any coagulation factor 2 to 3% and fibrinogen 8 mg/dL in an average adult. A dose of 10 to 15 mL of plasma per kg body weight will increase coagulation factors by 8 to 10%, while a dose of 30 to 35 mL per kg body weight will increase them by 30 to 35%.The lower dose corresponds to 3 to 6 bags of plasma in an average 70 kg adult, while the higher dose corresponds to 8 to 14 bags. The PT and PTT should be rechecked before subsequent units are transfused. If the PT and PTT remain prolonged, more plasma may be indicated.

FFP is the treatment of choice for congenital factor deficiencies when more specific concentrates are not available. Examples include factors V and XI.

Congenital Coagulation Factor Deficiencies

Dosing of plasma for congenital factor deficiencies is dependent upon the degree of factor deficiency and the half-life of the deficient factor(s).All of the factors noted above, except V and VII, have a half-life greater than 12 hours and do not need to be replaced more often than every 12 hours.A practical approach for an average adult would be to give:

1. Initial loading dose of 4 units of plasma prior to surgery
2. Maintenance dose of 2 units of plasma every 12 hours
3. Measure factor level after 24 hours
4. Readjust dose as needed

Plasma may be needed for massive transfusions of greater than one blood volume in patients who have a demonstrable coagulopathy and continued bleeding. Thrombocytopenia is responsible for continued bleeding during massive transfusion more often than coagulation factor depletion. Platelet transfusion should be tried first if the platelet count is <50,000/uL. Current massive transfusion guidelines recommend a 1 to 1 ratio of RBCs and plasma.

Plasma is indicated for the treatment of Thrombotic Thrombocytopenic Purpura (TTP) and hemolytic uremic syndrome (HUS). Plasma can be given as a continuous infusion or during plasma exchange. Continuous infusion is not recommended because of its increased risk of fluid overload. A single plasma exchange, which replaces approximately 60% of a patient's plasma volume, usually requires 10 to 12 units of plasma.

Plasma can be used for prophylaxis in patients with hereditary angioedema who are undergoing oral surgery. Prophylaxis will prevent attacks of angioedema which are commonly precipitated by dental procedures and head and neck surgery. Infusion of 2 units of FFP the day before and again just prior to the procedure is recommended. Although FFP is recommended for prophylaxis, its use for treatment of an angioedema attack has not been established. Plasma transfusions have been reported to arrest attacks of angioedema. However, FFP could be hazardous because it contains complement factors C2 and C4 that may exacerbate the attack.FFP should be reserved for life threatening attacks. Future treatment options include C1 Inhibitor concentrates that have been used for years in Europe and are currently under clinical investigation in the United States.

FFP should not be used as a volume expander, as a nutritional supplement, for the treatment of bleeding in the absence of documented coagulopathy, or as a standing order following surgery or massive transfusion.

It is important to remember that transfusion of FFP is not free of risk. FFP is the blood component most frequently associated with transfusion-related acute lung injury (TRALI). Today, TRALI is one of the most common causes of a fatal transfusion reaction. As with any other blood component, the decision to transfuse FFP should be based on predictable benefit and clinically necessity.