Blood Transfusion Essentials

Overview

Concise notes on blood transfusion products, indications, modifications, testing, complications, and management, with key thresholds and ratios for clinical use.

Blood Products and Core Properties

Packed RBCs (PRBCs): ~300 mL/unit; mainly RBCs, tiny plasma; ↑Hgb ~1 g/dL per unit.
Fresh Frozen Plasma (FFP): ~200–300 mL; all clotting factors, some fibrinogen and vWF.
Platelets: single donor unit or pooled apheresis (4–6 SD units); ↑Plt ~20–60K per SD unit.
Prothrombin Complex Concentrate (4-factor PCC): Factors II, VII, IX, X; rapid; small volume.
Cryoprecipitate: Very high fibrinogen; also vWF, Factor VIII, Factor XIII.

Structured Summary of Products, Contents, and Primary Indications

Product	Main Contents	Typical Dose/Form	Primary Use	Targets/Notes
PRBCs	RBCs; trace plasma	1 unit (~300 mL)	Anemia; hemorrhagic shock	↑Hgb ~1 g/dL per unit; MTP 1:1:1
FFP	All clotting factors; some fibrinogen, vWF	~200–300 mL/unit	Coagulopathy (cirrhosis, DIC, warfarin coagulopathy—less preferred than PCC), bleeding or pre-procedure with INR >1.6	Goal INR <1.6; thaw needed
Platelets	Platelets; trace plasma	Single donor unit or pooled (4–6 SD)	Thrombocytopenia; hemorrhagic shock	↑Plt ~20–60K per SD; thresholds 100K/50K/10K
4-factor PCC	II, VII, IX, X (±Protein C/S; tiny heparin)	Weight-based	Anticoagulant reversal (warfarin, DOACs)	Preferred over FFP; rapid, no thaw
Cryoprecipitate	Fibrinogen (high), vWF, VIII, XIII	Often 10 pooled units per dose	Hypofibrinogenemia (PPH, ruptured ectopic, DIC, massive bleed)	Give if fibrinogen <100–150; goal >150

Indications and Thresholds

PRBCs:
- Hemorrhagic shock: Activate MTP (PRBC:Plt:FFP = 1:1:1) until hemodynamically stable; obtain source control.
- Anemia: Transfuse at Hgb <7 g/dL (no CAD/CHF/cardiac surgery). Transfuse at Hgb <8 g/dL if CAD, CHF, cardiac surgery, or ACS risk.
Platelets:
- CNS bleed or neurosurgery: Transfuse if Plt <100,000/µL; aim >100K.
- Non-CNS bleed or non-neuro procedure: Transfuse if Plt <50,000/µL; aim >50K.
- Asymptomatic: Transfuse prophylactically if Plt <10,000/µL.
- Hemorrhagic shock: Include in MTP 1:1:1.
FFP:
- Coagulopathy (cirrhosis—production; DIC—consumption; warfarin coagulopathy—PCC preferred): Use guided by INR/PTT/fibrinogen or active bleeding.
- Bleeding or pre-procedure with INR >1.6 and unclear etiology: Consider FFP; aim INR <1.6.
- MTP component (1:1:1).
PCC:
- Warfarin reversal: PCC + Vitamin K; goal INR <1.6.
- DOAC (apixaban, rivaroxaban) bleed: PCC preferred; andexanet exists but not superior and very costly.
Cryoprecipitate:
- Hypofibrinogenemia: Fibrinogen <100–150 mg/dL with bleeding (PPH, ruptured ectopic, DIC, massive bleeding). Goal >150 mg/dL.
- Second-line for vWD or Hemophilia A if specific concentrates unavailable.

Modifications to Blood Products

Irradiation:
- Mechanism: X-ray/gamma-ray exposure to reduce donor T-cell proliferation.
- Prevents: Transfusion-associated graft-versus-host disease (TA-GvHD).
- Indications: Bone marrow transplant recipients, hematologic malignancies, congenital immunodeficiency/immunocompromised.
Leukoreduction:
- Mechanism: Remove donor WBCs.
- Prevents: Febrile non-hemolytic transfusion reactions; CMV transmission.
- Indications: History of frequent transfusions; immunocompromised (e.g., AIDS).
Washing:
- Mechanism: Remove plasma proteins (incl. IgA) and K+.
- Prevents: Allergic/anaphylactic reactions (esp. IgA deficiency); reduces hyperkalemia risk.
- Indications: IgA deficiency; recurrent allergic reactions; high K+ concern.

Pre-Transfusion Testing

Type and Screen (possible transfusion):
- Determine ABO and Rh antigens on RBCs.
- Antibody screen (indirect Coombs) against panel of minor RBC antigens; positive → further identification needed.
Type and Cross (probable transfusion; active bleeding or high-risk procedure):
- Includes type & screen.
- Crossmatch: Patient plasma + specific donor RBCs + Coombs reagent; no agglutination required to proceed.
Emergent transfusion: Give O negative when immediate transfusion is needed and testing cannot be completed.

Transfusion Complications (Acute <24 h; Delayed days–weeks)

FEVER HALO mnemonic:
- Fever: Febrile non-hemolytic transfusion reaction (FNHTR).
- H: Hemolytic reactions (acute and delayed).
- A: Allergic or Anaphylactic.
- L: Transfusion-related Acute Lung Injury (TRALI).
- O: Transfusion-Associated Circulatory Overload (TACO).

Complications: Mechanisms, Features, and Management

Complication	Mechanism	Timing	Key Features	Diagnostics	Management
FNHTR	Donor WBC cytokines; or recipient anti-HLA activate donor WBCs	1–6 h	Fever, chills; no hemolysis	Normal LDH/haptoglobin; DAT negative	Stop transfusion; APAP; prevent with leukoreduced blood
Acute Hemolytic TR	ABO incompatibility; intravascular hemolysis	<24 h (often <6 h)	Fever, hypotension, AKI, dark urine	↑LDH, ↓haptoglobin, DAT positive	Stop transfusion; supportive care; ensure future compatibility
Delayed Hemolytic TR	Alloantibodies to minor antigens (Duffy, Kell, Lewis); extravascular hemolysis	Days–weeks	Often asymptomatic; jaundice; splenomegaly	Hemolysis labs; history of prior transfusions	Usually self-limited; document antibodies
Allergic	Plasma proteins trigger IgE on mast cells	Within ~3–4 h	Urticaria, pruritus; no angioedema	Clinical	Stop briefly; antihistamines; restart slowly; prevent with washed blood if recurrent
Anaphylactic	IgA deficiency → anti-IgA IgE/mast cell degranulation	Within ~3–4 h	Urticaria, angioedema (eyes, lips, tongue), stridor, wheeze, hypotension, respiratory distress	Clinical	Stop transfusion; epinephrine (first-line), antihistamines, steroids; prevent with washed blood
TRALI	Donor anti-HLA/anti-neutrophil Abs + sequestered neutrophils → lung capillary injury; non-cardiogenic edema	≤6 h	Acute hypoxemia, ↑RR/work of breathing, bilateral infiltrates; fever/hypotension possible; no hypervolemia signs	CXR: bilateral diffuse opacities; normal BNP; no JVD/S3/edema	Stop transfusion; oxygen support (NC → BiPAP/vent)
TACO	Large/rapid volume; fluid retention (CHF, ESRD) → hypervolemia, cardiogenic edema	≤6 h	Dyspnea, hypoxemia, HTN, JVD, S3, pitting edema, ↑BNP; bilateral opacities	Signs of hypervolemia; CXR pulmonary edema	Stop transfusion; diuretics; oxygen support

Massive Transfusion Protocol (MTP) and Metabolic Issues

MTP Ratio: PRBC:Platelets:FFP = 1:1:1; consider cryoprecipitate if fibrinogen low.
Citrate toxicity: Hypocalcemia (citrate binds Ca2+) → worsened coagulopathy; monitor and replace calcium.
Hyperkalemia: Stored blood can raise K+; monitor ECG for peaked T, QRS widening.
Dilutional coagulopathy/thrombocytopenia: Large PRBC volumes dilute platelets and factors; prevent with 1:1:1.
Hypothermia and acidosis: Worsen coagulopathy; warm fluids/blood; manage acid-base status.

Type and Screen vs Type and Cross: Use Cases

Type and Screen: Possible transfusion (pre-procedure screening).
Type and Cross: Probable transfusion (active bleeding, high-risk surgery).
Emergency: O negative if no time for testing.

Key Terms & Definitions

MTP: Massive transfusion protocol; balanced resuscitation (1:1:1) to restore whole blood components.
PCC (4-factor): Concentrated vitamin K–dependent factors (II, VII, IX, X) for rapid reversal.
Cryoprecipitate: Plasma fraction rich in fibrinogen; also vWF, VIII, XIII.
DAT (Direct Antiglobulin Test): Detects antibodies bound to patient RBCs; positive in acute hemolytic TR.
TRALI vs TACO: TRALI = non-cardiogenic pulmonary edema without hypervolemia markers; TACO = cardiogenic pulmonary edema with hypervolemia signs.

Action Items / Next Steps

Select product by deficit and clinical context; apply thresholds (Hgb, Plt, INR, fibrinogen).
In hemorrhagic shock: Activate MTP (1:1:1); aim hemodynamic stabilization and source control.
For anticoagulant-related bleeding: Prefer PCC (+ Vitamin K for warfarin).
Pre-transfusion: Perform appropriate testing (type & screen vs type & cross); modify products (irradiate, leukoreduce, wash) based on risk.
Monitor during MTP: Calcium, potassium, temperature, acid-base, coagulation parameters.
At first sign of reaction: Stop transfusion; manage per reaction type (epinephrine for anaphylaxis; diuretics for TACO; respiratory support for TRALI).