Blood Component Therapy in Obstetrics

1. Indications for Blood Component Therapy in Obstetrics

• Postpartum hemorrhage (PPH): defined as blood loss ≥1,000 mL after any delivery, or any loss accompanied by signs of hypovolemia within 24 hours. Uterine atony accounts for >70% of cases.
• Placenta accreta spectrum: average blood loss of 3-5 L; requires planned massive transfusion preparation.
• Placental abruption: associated with consumptive coagulopathy and DIC.
• Obstetric DIC: triggered by abruptio placentae, retained dead fetus, amniotic fluid embolism, sepsis, or HELLP syndrome.
• HELLP syndrome: causes thrombocytopenia requiring platelet transfusion.
• Ectopic pregnancy / uterine rupture: acute massive hemorrhage.

2. Blood Components Used

A. Packed Red Blood Cells (PRBCs)

• Each unit raises hemoglobin by ~1 g/dL and hematocrit by ~3%.
• Indications: Hb <7 g/dL in stable patients; Hb <8-10 g/dL in actively bleeding or hemodynamically unstable patients.
• In massive obstetric hemorrhage, PRBCs are transfused in a 1:1:1 ratio with Fresh Frozen Plasma (FFP) and platelets to approximate whole blood reconstitution.
• Group O Rh(D)-negative blood is used in emergencies when the patient's type is unknown (especially important in females with childbearing potential).

B. Fresh Frozen Plasma (FFP)

• Contains all clotting factors, fibrinogen, and von Willebrand factor.
• Each unit (~250 mL) provides approximately 1 unit/mL of each clotting factor.
• Indications:
  • PT or APTT >1.5 times reference range
  • Active bleeding with coagulopathy
  • Massive transfusion (given in 1:1 ratio with PRBCs)
  • DIC with active hemorrhage
• Early aggressive FFP use, adapted from military trauma experience, improves outcomes in obstetric hemorrhage.
• Dose: 10-15 mL/kg.

C. Platelets

• One apheresis unit raises platelet count by ~30,000-60,000/µL; one pool of 4-6 random donor units raises it by ~30,000/µL.
• Indications:
  • Platelet count <50,000/µL with active bleeding
  • Platelet count <80,000/µL before neuraxial anesthesia (institutional variation)
  • Platelet count <100,000/µL in the presence of ongoing severe hemorrhage
  • HELLP syndrome with count <20,000/µL (prophylactic) or <50,000/µL (pre-procedure)
  • Glanzmann thrombasthenia: HLA-matched platelets used, cesarean reserved for obstetric indications only
• In a 1:1:1 massive transfusion protocol, platelets are given concurrently with PRBCs and FFP.

D. Cryoprecipitate

• Rich in fibrinogen (~300 mg/unit), Factor VIII, von Willebrand factor, Factor XIII, and fibronectin.
• Each unit raises fibrinogen by ~10 mg/dL; typical dose is 10 units (1-2 pools).
• Special importance in obstetrics: Fibrinogen levels in pregnancy are physiologically elevated (400-600 mg/dL); therefore, a "low-normal" fibrinogen level (e.g., 200 mg/dL) may actually represent significant depletion.
• Decreased fibrinogen levels strongly correlate with the severity of PPH and can predict developing coagulopathy.
• Indications:
  • Fibrinogen <200 mg/dL (obstetric threshold higher than surgical threshold of 100 mg/dL)
  • DIC with hypofibrinogenemia
  • Massive obstetric hemorrhage (early administration recommended)
• Cryoprecipitate or fibrinogen concentrate should be considered early in obstetric hemorrhage resuscitation. - Barash Clinical Anesthesia, 9e; Miller's Anesthesia, 10e

E. Fibrinogen Concentrate

• An alternative to cryoprecipitate in some centers; dose-controlled, virally inactivated.
• Increasingly used when fibrinogen is critically low, particularly early in PPH.

3. Massive Transfusion Protocol (MTP) in Obstetrics

• Early activation once hemorrhage is recognized (do not wait for laboratory values in active bleeding).
• Fixed ratio transfusion: PRBCs : FFP : Platelets = 1:1:1 (e.g., 6 units PRBCs + 6 units FFP + 1 apheresis platelet unit per cycle).
• Fibrinogen/cryoprecipitate early - given the rapid consumptive and dilutional coagulopathy in PPH.
• Avoid the "lethal triad": hypothermia, acidosis, and coagulopathy - each worsens the other.
• Viscoelastic hemostatic assays (TEG/ROTEM): provide real-time assessment of clot formation, fibrinolysis, and platelet function to guide goal-directed component therapy and reduce unnecessary transfusion. - Creasy & Resnik's Maternal-Fetal Medicine

4. Tranexamic Acid (TXA) - Adjunct to Blood Component Therapy

• WOMAN trial (20,060 women, RCT): tranexamic acid given within 3 hours of PPH diagnosis reduced death due to bleeding (RR 0.69; 95% CI 0.52-0.91; p = 0.008) with no increase in thromboembolic events.
• ACOG recommends TXA when initial uterotonic therapy fails; it should be administered before the cord is clamped to avoid neonatal exposure (it crosses the placenta).
• Dose: 1 g IV over 10 minutes; repeat if bleeding continues after 30 minutes. - Miller's Anesthesia, 10e

5. Cell Salvage (Intraoperative Autotransfusion)

• Historically avoided due to concerns about amniotic fluid contamination and rhesus sensitization.
• Now widely used with a leukocyte reduction filter which effectively removes fetal squamous cells, tissue factor, alpha-fetoprotein, and bacteria.
• Particularly valuable for Jehovah's Witness patients who refuse allogeneic blood.
• Cost-effective in massive obstetric hemorrhage.
• In Rh-negative parturients: administer anti-D immunoglobulin post-procedure.

6. Special Situations

DIC in Obstetrics

• Management: treat the underlying cause + FFP (for clotting factors) + cryoprecipitate (for fibrinogen) + platelets; avoid prophylactic FFP as it obscures PT results.

Rh-Negative Mothers

• Use Rh(D)-negative PRBCs when blood type is unknown.
• Administer anti-D immunoglobulin after transfusion of Rh-positive products or cell salvage.

Preeclampsia/HELLP

• Platelet transfusion when count <20,000/µL (spontaneously) or <50,000/µL before cesarean section.
• FFP for associated DIC.

7. Monitoring and Safety

• Pre-transfusion testing: ABO/Rh typing, crossmatch; do not delay in emergency - use O-negative uncrossmatched.
• Monitor CBC, PT, APTT, fibrinogen, and TEG/ROTEM serially.
• Watch for transfusion complications: TRALI, TACO, febrile non-hemolytic reactions, ABO incompatibility, infection.
• All obstetric units should have a documented massive transfusion protocol with antepartum hemorrhage risk stratification, rapid response team activation, and blood bank coordination. - Barash Clinical Anesthesia, 9e

Summary Table