Perinatology.com
Perinatology.com
OBRx — Blood Component Therapy

Blood Component Therapy

Clinical reference for transfusion of red blood cells, platelets, plasma, and cryoprecipitate in obstetrics.

For healthcare professionals. Use in conjunction with institutional massive transfusion protocols and blood bank guidance.

Obstetric Massive Transfusion (At-a-Glance Ratios)

When hemorrhage is life-threatening or evolving rapidly, initiate your institution’s OB MTP early and coordinate with blood bank. Ratios below are commonly used starting points while laboratory-guided hemostatic resuscitation is arranged.

Strategy Typical Initial Ratio Practical “Pack” Example Notes
Balanced component resuscitation RBC : Plasma : Platelets ≈ 1 : 1 : 1 e.g., 4 RBC + 4 Plasma + 1 Apheresis Platelets Common MTP framework; tailor to labs/viscoelastic testing and clinical response.
Alternative “plasma-forward” RBC : Plasma ≈ 1 : 1 (platelets added early) 2 RBC + 2 Plasma, then platelets as soon as available Used when platelets are delayed; avoid platelet under-resuscitation in ongoing massive bleeding.
Fibrinogen-first (OB emphasis) Add cryo early when fibrinogen is low Give 10 units cryo (or per protocol) then recheck OB hemorrhage often features early hypofibrinogenemia; many protocols target fibrinogen ≥200 mg/dL in PPH.
Reminder: Ratios are a bridge while transitioning to laboratory-guided therapy (CBC, PT/INR, aPTT, fibrinogen; consider viscoelastic testing where available).

At-a-Glance Dosing (Adults)

Component Indications Typical Dose Expected Effect
Packed RBCs Symptomatic anemia, hemorrhage 1 unit (~250 mL) ↑ Hgb ~1 g/dL (Hct ~3%)
Platelets Bleeding or severe thrombocytopenia 1 apheresis unit
or 4–6 pooled units		 ↑ platelets 30–60 ×10⁹/L
Plasma (FFP) Coagulopathy, massive transfusion 10–20 mL/kg Replaces clotting factors
Cryoprecipitate Fibrinogen <100–150 mg/dL (often treat earlier in PPH) 1 unit / 10 kg (≈10 units) ↑ fibrinogen ~50 mg/dL (approx.)

Cryoprecipitate Calculator (Estimated Units to Raise Fibrinogen)

Educational estimate based on classic assumptions: blood volume ≈ 70 mL/kg; cryo fibrinogen content ≈ 150 mg/unit. Real-world fibrinogen content varies by product and pooling; follow local protocol and repeat labs.

Enter values and click Calculate.
Formula used (classic):
Blood volume (mL) = weight(kg) × 70
Plasma volume (mL) = blood volume × (1 − hematocrit)
Fibrinogen required (mg) = (desired − initial) × (plasma volume / 100)
Cryo units ≈ fibrinogen required / 150

Red Blood Cells

Indicated for symptomatic anemia or acute blood loss. Transfusion rarely indicated if Hgb >10 g/dL and almost always indicated if <6 g/dL.

  • Start slowly (2 mL/min) for first 15 min
  • Complete transfusion within 4 hours
  • Use leukoreduced and irradiated products when indicated

Platelets

Used for bleeding or prophylaxis in severe thrombocytopenia.

  • <10 ×10⁹/L (prophylaxis)
  • <50 ×10⁹/L with bleeding or procedures
  • >100 ×10⁹/L for neurosurgery

Use irradiated platelets in patients at risk for TA-GVHD.

Plasma (FFP)

Contains all coagulation factors.

  • Massive transfusion
  • PT/INR or aPTT >1.5× normal with bleeding
  • Urgent warfarin reversal (with vitamin K)

Cryoprecipitate

Concentrated fibrinogen, factor VIII, XIII, vWF.

  • Preferred fibrinogen replacement in obstetric hemorrhage
  • Many OB protocols target fibrinogen ≥200 mg/dL in PPH

Precautions & Risks

  • All components must be transfused through approved filters
  • Risk of TACO, TRALI, hemolytic reactions
  • Transfusion-transmitted infection risk is extremely low in the U.S.
  • Begin transfusions slowly—severe reactions can occur after small volumes
  • Complete a unit within 4 hours (standard blood banking safety practice)

References

  1. AABB. Circular of Information for the Use of Human Blood and Blood Components. (current edition).
  2. ACOG Practice Bulletin: Postpartum Hemorrhage. Obstet Gynecol.
  3. SMFM Consult Series: Massive Transfusion in Obstetrics. Am J Obstet Gynecol.
  4. Bakdash S, Yazer MH. What every physician should know about transfusion reactions. CMAJ. 2007.
  5. FDA. Guidance / Circular of Information resources for blood components.