Understanding Fresh Frozen Plasma
Blood comprises two main components: cellular elements (red cells, white cells, platelets) and plasma, the liquid matrix. Plasma constitutes roughly 55% of total blood volume and serves as the transport medium for critical proteins including coagulation factors, immunoglobulins, and albumin.
Fresh frozen plasma is plasma separated from whole blood and cryopreserved within 8 hours of collection, preserving the full complement of coagulation factors at donation levels. An adult typically carries approximately 3 litres of circulating plasma. When bleeding or coagulopathy develops, FFP restores both factor concentration and clotting capacity.
FFP carries no red cell antigens, making AB plasma universally compatible; O group is the universal red cell donor, not plasma donor. Administered FFP takes effect within minutes, though optimal results depend on adequate thawing (30 minutes in a water bath) and bedside cross-matching verification.
FFP Dosing Calculation
Weight-based dosing is the standard approach in transfusion medicine. A dose of 10–20 mL/kg increases circulating coagulation factor levels by 20–30%, with 12–15 mL/kg as the typical therapeutic range for acute bleeding or prophylaxis.
Total plasma volume (mL) = Patient weight (kg) × Dose (mL/kg)
Number of units = ⌈Total plasma volume ÷ Unit volume⌉
Patient weight— Body weight in kilogramsDose— Therapeutic dose in mL per kg; typically 10–20 mL/kg, commonly 12–15 mL/kgUnit volume— Volume per FFP unit, usually 250 mL (standard) or 200 mL (variable by blood bank)Total plasma volume— Total millilitres of FFP to administerNumber of units— Rounded-up whole units required to meet the calculated dose
Clinical Indications for FFP Transfusion
FFP is reserved for documented or suspected coagulation factor deficiency with active bleeding or high bleeding risk. Key indications include:
- Massive haemorrhage: Ongoing bleeding requiring multiple red cell units or in hypotensive, non-responsive patients
- Congenital or acquired factor deficiency: Haemophilia, hepatic insufficiency, or disseminated intravascular coagulation (DIC)
- Warfarin overdose: When fresh frozen plasma is needed prior to vitamin K effect (though prothrombin complex concentrate is now preferred)
- Thrombotic thrombocytopenic purpura (TTP): Plasma exchange with FFP replacement
- Pre-operative prophylaxis: In patients with known factor deficiencies undergoing invasive procedures
FFP should not be used for simple volume replacement, hypoalbuminaemia alone, or immunoglobulin supplementation—more targeted products exist for these purposes.
Administration and Safety Checks
Before infusing FFP, complete a formal compatibility check: two qualified staff members must verify the unit's ABO group at the bedside against the patient's identification. FFP must be thawed in a temperature-controlled water bath (37°C) for approximately 30 minutes; never use a microwave or boiling water.
Infuse one unit over 30 minutes at minimum, and complete all units within 4 hours of thawing to prevent bacterial contamination and factor degradation. Keep the patient under continuous observation during transfusion to detect transfusion reactions (fever, chills, dyspnoea, rash, chest or back pain). Each transfusion should be preceded by a documented clinical indication and a baseline coagulation screen (INR, aPTT, or point-of-care testing in emergencies).
Once thawed, FFP deteriorates rapidly; discard any unused portion after 4 hours. Do not re-freeze thawed plasma, and always remove FFP from storage only when immediate use is planned.
Practical Considerations for FFP Dosing
Several pitfalls and real-world challenges affect FFP dosing decisions in the clinical setting.
- Do not overdose empirically — Administering excessive FFP in the absence of documented factor deficiency increases transfusion-related acute lung injury (TRALI) risk and volume overload. Always confirm laboratory evidence of coagulopathy (elevated INR, prolonged aPTT) or active bleeding before escalating dose beyond 15 mL/kg. Repeat coagulation tests 1 hour post-transfusion to reassess.
- Account for massive transfusion protocols — In severe haemorrhage, FFP is often given as part of a 1:1:1 ratio with red cells and platelets rather than by weight-based dosing alone. Check your hospital's massive transfusion protocol; local guidelines may override standard mL/kg calculations to maintain haemostatic balance during ongoing bleeding.
- Remember unit volumes vary by blood bank — While 250 mL is standard in many countries, some centres stock 200 mL or 300 mL units. Verify your blood bank's unit volume before calculating the number of units required. Using the wrong denominator will miscalculate unit needs and delay transfusion.
- Fresh frozen plasma has limited half-life — Infused coagulation factors survive only 3–5 days in vivo. Recurrent bleeding in a patient transfused 1 week earlier does not reflect failed prior transfusion but rather consumption or ongoing synthesis failure. Reassess the underlying cause (liver disease, DIC, ongoing anticoagulation) rather than simply re-transfusing.