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Transfusion Medicine & Reactions

Name: Transfusion Medicine & Reactions
Creator: Veli Bakalov, MD

The right threshold, the right product, and the reaction you must name in seconds

Hematology/Oncology·Hemostasis, Thrombosis & Transfusion·4 min read·9 high-yield points·Reviewed by Veli Bakalov, MD @HemeOncBuddy

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Restrictive triggers: RBCs at Hb <7 g/dL (<8 with cardiac disease or postoperatively; each unit raises Hb ~1 g/dL); platelets <10,000 prophylaxis, <20,000 with fever, <50,000 for procedures or bleeding, <100,000 for neurosurgery or eye surgery.
FFP = all coagulation factors (multifactor coagulopathy, DIC, warfarin reversal if no PCC); cryoprecipitate = fibrinogen, VIII, XIII, vWF, fibronectin (fibrinogen <100–150 mg/dL, DIC).
Febrile nonhemolytic reaction is the most common (fever 1–6 hours in, donor leukocyte cytokines) → rule out hemolysis, antipyretics; prevent with leukoreduction.
Anaphylaxis during a first transfusion: classically IgA deficiency with anti-IgA (a minority of cases; haptoglobin deficiency and other plasma protein antibodies also occur, and many have no cause found) → epinephrine, then washed or IgA-deficient products.
Acute hemolytic reaction = ABO incompatibility from a clerical error: within minutes, fever, flank pain, hemoglobinuria, hypotension, DIC → stop, IV fluids, support; delayed hemolytic = days to 2 weeks, minor antigens (Kidd, Duffy, Rh), positive DAT.
TRALI: non-cardiogenic edema within 6 hours (donor anti-HLA/anti-neutrophil antibodies), hypotension, normal JVP/BNP, no diuretic response; TACO: hypertension, high JVP/BNP, improves with diuretics.
Irradiation prevents transfusion-associated GVHD (transplant, immunodeficiency, neonates, Hodgkin, relative donors); leukoreduction prevents fever, CMV, HLA alloimmunization; washing is for IgA deficiency.
Massive transfusion (>10 units in 24 h): citrate → hypocalcemia and hypomagnesemia, plus hyperkalemia, hypothermia, metabolic alkalosis, dilutional coagulopathy → balanced 1:1:1 resuscitation.
RhoGAM for RhD-negative mothers at 28 weeks, within 72 hours of delivery of an RhD-positive infant, and after any sensitizing event.

Thresholds and products

Restrictive is the rule. Transfuse packed red cells for hemoglobin <7 g/dL in most stable patients, and <8 g/dL with active cardiac disease or after surgery; restrictive triggers match or beat liberal ones for outcomes. One unit raises hemoglobin by about 1 g/dL (hematocrit ~3%), so recheck before giving more to a non-bleeding patient. Active hemorrhage is transfused on clinical grounds, not a number.

Blood products and their triggers

Product	Contains	Main indications and triggers
Packed red cells	Red cells	Hb <7 g/dL (<8 with cardiac disease or postoperatively); active hemorrhage
Platelets	Platelets	<10,000 prophylaxis against spontaneous bleeding; <20,000 with fever or sepsis; <50,000 before an invasive procedure or with active bleeding; <100,000 before neurosurgery or ocular surgery
Fresh frozen plasma	All coagulation factors	Multifactor coagulopathy with bleeding, DIC, urgent warfarin reversal (PCC preferred if available)
Cryoprecipitate	Concentrated fibrinogen, factors VIII and XIII, vWF, fibronectin	Hypofibrinogenemia (below ~100–150 mg/dL), DIC

Platelets follow a 10–50–100 rule; FFP is multifactor, cryoprecipitate is targeted repletion.

Avoid platelet transfusion in TTP and HIT unless bleeding is life-threatening: it fuels thrombosis.

Compatibility and product modifications

Type and screen vs crossmatch. Type and screen determines the recipient's ABO/Rh type and screens the serum for unexpected antibodies. A crossmatch mixes recipient serum with the specific donor unit to confirm compatibility before release. O-negative is the universal RBC donor (given uncrossmatched in emergencies), AB is the universal plasma donor, and AB-positive is the universal RBC recipient.

Leukoreduced: removes donor white cells, cutting febrile reactions, CMV transmission, and HLA alloimmunization.
Irradiated: inactivates donor T cells to prevent transfusion-associated graft-versus-host disease in immunocompromised recipients: stem cell transplant, congenital immunodeficiency, neonates, Hodgkin lymphoma, and directed donations from relatives.
Washed: removes plasma, for IgA deficiency or recurrent severe allergy.

Transfusion-associated GVHD (fever, rash, diarrhea, hepatitis, and pancytopenia 1–2 weeks after transfusion) is usually fatal, so prevention is everything; leukoreduction alone does not prevent it.

Recognizing transfusion reactions

First steps for any reaction. Stop the transfusion, keep the line open with saline, recheck the patient's identity against the unit, and send the bag with a fresh sample to the blood bank (repeat type and crossmatch, direct antiglobulin test, hemolysis labs, urinalysis for hemoglobin).

Classic transfusion reactions

Reaction	Timing	Mechanism	Clues	Management
Febrile nonhemolytic (most common)	1–6 hours	Cytokines released by donor leukocytes; recipient antibodies to donor WBCs	Fever and chills without hemolysis	Stop to rule out hemolysis, antipyretics; prevent with leukoreduction
Allergic	Minutes	Recipient antibodies to donor plasma proteins	Urticaria, pruritus	Antihistamine; may continue if mild
Anaphylactic	Minutes, even with the first-ever transfusion	Classically anti-IgA antibodies in an IgA-deficient recipient (a minority of cases; also haptoglobin deficiency or other plasma protein antibodies; often no cause found)	Hypotension, wheezing, angioedema	Epinephrine; future washed or IgA-deficient products
Acute hemolytic	Minutes	ABO incompatibility: preformed IgM, complement-mediated intravascular hemolysis (type II hypersensitivity)	Fever, flank or back pain, hemoglobinuria, hypotension, DIC, renal failure; positive DAT	Stop immediately, IV fluids, support
Delayed hemolytic	Days to 2 weeks	Anamnestic response to minor antigens (Rh, Kidd, Duffy)	Gradually falling Hb, mild jaundice, positive DAT; extravascular	Usually mild; supportive
Septic	Minutes to hours	Bacterial contamination, most often platelets (stored at room temperature)	High fever, rigors, hypotension	Stop; culture patient and bag; broad-spectrum antibiotics

The ABO-incompatible reaction is almost always a clerical or mislabeling error; the bedside identity check of patient and unit prevents most fatal reactions.

TRALI vs TACO

TRALI is non-cardiogenic pulmonary edema within 6 hours of transfusion: donor anti-HLA or anti-neutrophil antibodies activate recipient neutrophils in the lung. Expect bilateral infiltrates, hypoxia, fever, and hypotension with normal jugular venous and wedge pressures. It is a leading cause of transfusion-related death; treatment is supportive and respiratory, and most patients recover within days.

TACO is hydrostatic pulmonary edema from too much volume too fast in elderly, cardiac, or renal patients. Hypertension, elevated JVP and BNP, and improvement with diuretics distinguish it from TRALI. Prevent it by transfusing slowly and diuresing between units.

TRALI vs TACO

Feature	TRALI	TACO
Mechanism	Immune, non-cardiogenic (anti-HLA/anti-neutrophil antibodies)	Hydrostatic volume overload
Blood pressure	Hypotension	Hypertension
JVP, wedge, BNP	Normal	Elevated
Diuretics	No response	Improves
Setting	Within 6 hours; any recipient	Too much volume, too fast; elderly, cardiac, renal

Massive transfusion and Rh prophylaxis

Massive transfusion (over ~10 units in 24 hours) risks:

Dilutional thrombocytopenia and coagulopathy
Hypocalcemia and hypomagnesemia, because the citrate anticoagulant chelates them (perioral tingling, tetany, prolonged QT)
Hyperkalemia, hypothermia, and metabolic alkalosis as citrate is converted to bicarbonate

Resuscitate with a balanced 1:1:1 ratio of red cells, plasma, and platelets, and replace calcium.

Rh(D) prophylaxis. An RhD-negative mother carrying an RhD-positive fetus can form anti-D antibodies that cause hemolytic disease of the newborn in future pregnancies; the first is usually spared. Give Rho(D) immune globulin (RhoGAM) to the unsensitized mother at 28 weeks, within 72 hours of delivery if the newborn is RhD-positive, and after any sensitizing event (miscarriage, amniocentesis, trauma, bleeding). The Kleihauer-Betke test quantifies fetomaternal hemorrhage to guide the dose.