Blood Products and Transfusion

In depth

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Oxygen delivery, hemostasis and stored blood

Red cells restore oxygen delivery: DO₂ = cardiac output × CaO₂ × 10, with CaO₂ = (1.34 × Hgb × SaO₂) + (0.003 × PaO₂). At Hgb 15 g/dL, SaO₂ 98% and cardiac output 5 L/min, DO₂ is about 1,000 mL/min against a resting VO₂ of 250 mL/min, an extraction of 25%. Anemia is tolerated by raising cardiac output and extraction: resting volunteers hemodiluted to Hgb 5 g/dL had no rise in lactate (Weiskopf, JAMA 1998). The heart already extracts 70–75% at rest and can meet more demand only with more coronary flow, which a stenosis limits, so thresholds are higher in coronary disease.

Over up to 42 days of storage at 1–6 °C, 2,3-DPG falls (shifting the curve left until it regenerates), potassium leaks out, faster after irradiation, and the cells stiffen. Fresher units showed no benefit in ABLE, RECESS, INFORM and TRANSFUSE (2015–2017), so banks issue the oldest compatible unit first.

Hemostasis fails in order: with red cell and crystalloid or colloid replacement, fibrinogen reaches a critical 100 mg/dL after about 142% of blood volume is lost, platelets 50,000/µL only at about 230% (Hiippala 1995). Hypothermia (about 10% loss of clotting function per 1 °C), acidosis and hypocalcemia worsen it, and PT and aPTT miss hypothermia and hypocalcemia because they run at 37 °C on recalcified plasma (European trauma guideline 2023).

The products: storage, dose and expected increment

Plasma (200–250 mL a unit) needs ABO compatibility but no crossmatch, and thawing at 30–37 °C takes time, so trauma centers keep thawed or liquid plasma ready. Volume limits it: 15 mL/kg in an 80 kg adult is 1,200 mL, and an INR of 1.5–1.7 already means at least 30% factor activity that a standard dose may not normalize (Circular 2024).

Room-temperature storage makes platelets the component most likely to carry bacteria, so units are tested or pathogen reduced; transfused platelets survive 3–4 days. For a poor rise, check a count 10–60 minutes after the dose: corrected count increment (CCI) = (post − pre count) × BSA (m²) ÷ platelets given (× 10¹¹). A 1-hour CCI below about 5,000–7,500 suggests HLA or platelet antibodies (give HLA-matched or crossmatched platelets); a good 1-hour but poor 24-hour count suggests consumption by fever, sepsis, DIC, splenomegaly or bleeding (Circular 2024).

Each cryo unit holds at least 150 mg fibrinogen and 80 IU factor VIII plus von Willebrand factor and factor XIII; fibrinogen recovery is 50–60%, and thawed cryo is kept at room temperature and given within 4–6 hours (Circular 2024). Early empiric cryo in trauma hemorrhage did not lower 28-day mortality (CRYOSTAT-2, JAMA 2023: 25.3% vs 26.1%).

4F-PCC brought the INR to 1.3 or less at 30 minutes in 62.2% of bleeding warfarin patients vs 9.6% with plasma (Sarode, Circulation 2013); give vitamin K with it because the infused factors wear off within hours. Fibrinogen concentrate 4 g was noninferior to 10 units of cryo for bleeding after cardiac surgery (FIBRES, JAMA 2019), and Fibryga gained a US label for acquired deficiency in 2024.

Low-titer group O whole blood carries red cells, plasma and platelets in one bag; anti-A and anti-B titer cutoffs are set locally, and none is proven safe (Circular 2024). Two 2026 NEJM prehospital trials found no advantage over components: SWiFT (death or massive transfusion by 24 hours 48.7% vs 47.7%) and TOWAR (1,020 air medical patients; 30-day mortality 25.9% vs 20.5%, not significant). The in-hospital TROOP trial continues.

Special products: irradiated, leukoreduced, CMV-safe, washed

Irradiate cellular products for stem cell transplant recipients, severe cellular immunodeficiency, intrauterine and at-risk neonatal transfusion, patients on purine analogues such as fludarabine, granulocytes, and units from relatives or HLA-selected donors; HIV infection alone is not an indication. Leukoreduction is no substitute, because enough T cells remain to cause TA-GVHD. Irradiated red cells expire 28 days after irradiation and carry more potassium, and washed units expire 24 hours after processing. Bedside leukoreduction filters can cause sudden hypotension in patients on ACE inhibitors (Circular 2024).

Compatibility, pretransfusion testing and emergency release

ABO antibodies are naturally occurring IgM that fix complement, so incompatible red cells hemolyze in the vessels within minutes. Red cells must suit the recipient's plasma and plasma the recipient's red cells, so group O is the universal red cell donor and AB the universal plasma donor. Anti-D forms only after transfusion or pregnancy and threatens later pregnancies with hemolytic disease of the fetus and newborn.

In a life-threatening emergency the bank releases uncrossmatched group O red cells (O negative for girls and women of childbearing potential, often O positive for others), AB or low-titer A plasma, and cryo of any group; the ordering provider signs the release, often afterward. Draw the type and screen before the first unit, because large volumes of group O cells and out-of-group plasma confuse later typing. Label every tube at the bedside from the armband, never in advance: most ABO-incompatible transfusions begin with an identification error (Circular 2024).

Thresholds: red cells, platelets and plasma

TRICC and TRISS made 7 g/dL the ICU default, TRACS and TRICS-III support a restrictive 7.5 in cardiac surgery, and FOCUS supports 8 with heart disease or orthopedic surgery (AABB 2023). MINT missed significance but leaned liberal, and the 2025 AABB MI guideline suggests 10. In brain injury only TRAIN was positive, and practice varies. In a stable patient who is not bleeding, give one unit and reassess before the next (AABB Choosing Wisely).

Avoid platelets in HIT, TTP and ITP unless bleeding is life-threatening, above 100,000 without platelet dysfunction, and in nonbleeding patients on antiplatelet drugs (Circular 2024); uremic bleeding calls for desmopressin and dialysis. Plasma has no numeric trigger: it is for bleeding or urgent procedures with multiple factor deficiencies, massive transfusion, TTP exchange and warfarin reversal when PCC is unavailable, not for volume or an INR of 1.7 or less (Circular 2024). In cirrhosis the INR overstates bleeding risk, and AASLD guidance (2020) advises against correcting it with plasma before procedures.

Massive transfusion and viscoelastic testing

Massive transfusion is classically 10 or more red cell units in 24 hours, but activation is predictive: an ABC score of 2 or more (penetrating mechanism, SBP 90 or less, HR 120 or more, positive FAST; Nunez 2009). In PROPPR (JAMA 2015, 680 patients), 1:1:1 vs 1:1:2 did not significantly change 30-day mortality (22.4% vs 26.1%) but achieved hemostasis more often (86% vs 78%), with fewer exsanguination deaths at 24 hours (9.2% vs 14.6%).

The European trauma guideline (2023) targets systolic pressure 80–90 mmHg (MAP 50–60) until bleeding is controlled, or MAP 80 or more with severe TBI. It gives 3–4 g of fibrinogen (15–20 single cryo units or concentrate) when fibrinogen is 150 mg/dL or less or viscoelastic tests show a deficit, keeps platelets above 50,000 (100,000 with TBI) and ionized calcium at 1.1–1.3 mmol/L with calcium chloride, and gives TXA within 3 hours without waiting for test results. Nursing: a rapid infuser with a warmer, large-bore access, one person tracking products, and serial calcium, potassium, temperature and coagulation checks.

Cutoffs vary by device and program. Denver rapid-TEG thresholds were ACT 128 s or more, angle 65° or less, MA 55 mm or less and LY30 5% or more (Einersen 2017), while Moore (2014) calls LY30 above 3% hyperfibrinolysis. A European ROTEM algorithm uses FIBTEM CA5 below 10 mm for fibrinogen and EXTEM minus FIBTEM CA5 below 30 mm for platelets (Baksaas-Aasen 2019).

A single-center trial favored TEG-guided resuscitation (28-day mortality 19.6% vs 36.4%; Gonzalez 2016), but the multicenter iTACTIC trial (396 patients) found no difference when both arms began with empiric ratios (25% vs 28%). Standard TEG and ROTEM do not detect aspirin or P2Y12 inhibitor effect.

Giving blood safely: verification, equipment, rates

1. Before: an order (product, volume, rate, modifications), consent, baseline vital signs with SpO₂, and 20–24 gauge access by vein size, larger for rapid transfusion (INS 2021).
2. At the bedside: match two identifiers on the armband to the unit tag and label, then ABO/Rh, unit number, expiration and special requirements; reject clots, leaks, cloudiness or a bag darker than its segments.
3. Equipment: a 150–260 micron filter set primed with 0.9% NaCl (Circular 2024); a fresh set for platelets, blood-approved pumps, and pressure bags no higher than 300 mmHg (BCSH 2009).
4. Timing: one unit at a time, finished within 4 hours of spiking (Circular 2024); vital signs before, at 15 minutes and at completion (New York State 2012).

Warm blood for rapid or massive transfusion, exchange transfusion and cold-reactive antibodies with FDA-cleared devices only (Circular 2024); UK guidance warms adults receiving more than 50 mL/kg/h, and never improvise with hot water or a microwave (BCSH 2009). The Joint Commission's 2026 goals require two identifiers but no longer spell out a two-person check, so policy chooses two licensed staff or barcode scanning. Document the check, unit numbers, times, volume, vital signs and response.

Transfusion reactions: recognition and response

Treat any new symptom during or after a transfusion as a reaction, because early hemolysis, sepsis, TRALI and febrile reactions look alike. Restart the same unit only under transfusion service protocol, in practice for isolated hives (Circular 2024).

1. Stop the transfusion, keep the vein open with 0.9% NaCl through new tubing, and treat: IM epinephrine for anaphylaxis, oxygen, fluids, vasopressors.
2. Recheck the armband against the unit label and tag; an ID error may mean another patient is about to receive the wrong unit.
3. Notify the provider and blood bank; return the bag with tubing and attached fluids.
4. Send a post-reaction sample from another site (DAT, repeat ABO/Rh, hemolysis labs), urine for hemoglobin, cultures for a 2 °C rise or rigors, and a chest film and BNP for respiratory signs; document and report (NHSN).

Acute hemolysis usually follows an identification error. Symptoms can start after a small volume, and anesthetized patients may show only hypotension, hemoglobinuria and oozing; care supports blood pressure, corrects DIC and keeps urine flowing (Circular 2024). Febrile reactions follow under 1% of leukoreduced red cell units but about 5% of leukoreduced apheresis platelets (Circular 2024); premedication does not prevent them (Kennedy 2008) and can mask the fever of hemolysis or sepsis.

TRALI is a two-hit injury: primed neutrophils meet donor anti-HLA or anti-HNA antibodies, usually in plasma-rich products from donors sensitized by pregnancy, and male-donor plasma has cut TRALI deaths (Circular 2024). NHSN requires onset within 6 hours, PaO₂/FiO₂ 300 or less or SpO₂ below 90% on room air, bilateral infiltrates and no left atrial hypertension; care is supportive, without diuretics if hypotensive, and the bank retrieves the donor's other components. TACO needs 3 or more findings within 12 hours, including respiratory distress or pulmonary edema plus raised BNP, cardiovascular changes or fluid overload (NHSN). Prevent it in older patients and in heart failure, kidney disease or chronic anemia with single units, slow rates and, selectively, a diuretic (BCSH 2009).

Anaphylaxis is rare (under 10 per 100,000 units) and mostly unexplained, though IgA and haptoglobin deficiency are described; later cellular units may be washed. Septic reactions come mainly from skin flora in platelets and cold-growing organisms such as Yersinia in red cells: culture the patient, bag and set, start antibiotics, and the bank recalls co-components (Circular 2024).

Jehovah's Witness patients and bloodless care

Jehovah's Witnesses decline whole blood and its four primary components: red cells, white cells, platelets and plasma. Fractions (albumin, cryoprecipitate, PCC, fibrinogen concentrate, immunoglobulins) and procedures that keep blood in a continuous circuit, such as cell salvage and hemodilution, are individual choices; stored autologous blood is generally declined. Ask privately, item by item, document each choice and look for an advance directive card. A competent adult's refusal stands even if death may follow; minors raise legal questions that vary by state, and Hospital Liaison Committees can help.

• Before surgery: treat anemia (IV iron, B12, folate, ESA) and arrange cell salvage.
• Limit phlebotomy: small-volume tubes and only tests that change care.
• Bleeding: early surgical or interventional control, TXA, accepted factor concentrates, vitamin K, desmopressin.
• Severe anemia: lower oxygen demand (sedation, ventilation, fever control), raise FiO₂, give ESA with IV iron.

Exam pearls

• 1 unit of red cells raises Hgb about 1 g/dL (Hct 3%); 1 apheresis platelet unit, 30,000–60,000/µL; 1 cryo unit per 7–10 kg, fibrinogen 50–75 mg/dL.
• Thresholds: 7 g/dL in most ICU patients (TRICC, TRISS), 7.5 in cardiac surgery, 8 with heart disease, 10 in acute MI (MINT, AABB 2025).
• Acute hemolysis: fever, flank pain, hypotension and dark urine within minutes, usually from an identification error.
• TRALI: within 6 h, hypoxemia, BP normal or low, no diuretic response. TACO: within 12 h, hypertension, high BNP, diuretic response.
• Anaphylaxis: no fever, minutes, epinephrine; IgA deficiency with anti-IgA needs washed or IgA-deficient products.
• Septic reaction: temperature up 2 °C or more, rigors, hypotension; most often platelets.
• Irradiation prevents TA-GVHD; leukoreduction prevents febrile reactions, HLA alloimmunization and CMV, not TA-GVHD.
• TEG: long R, give plasma; low angle, cryo; low MA, platelets; high LY30, TXA.