Low-Titer O Whole Blood (LTOWB)

Emergency & Prehospital

• Life-threatening traumatic hemorrhage with shock: this is the core indication. The 2025 NAEMSP position names low-titer group O whole blood (LTOWB) the first-choice prehospital product where a high-quality program exists. It also prefers blood components over crystalloid. Here's the catch: two 2026 randomized trials did not show a survival advantage over components (see Clinical Pearls).
• Adult shock criteria: systolic BP below 90 mmHg or weak radial pulse; heart rate above 100 that does not respond to fluids; or shock index above 1.0 (heart rate divided by systolic BP). Altered mental status, delayed capillary refill and end-tidal CO₂ below 25 mmHg are listed as clinical signs. How protocols combine these items varies.
• Non-traumatic life-threatening hemorrhage: gastrointestinal, peripartum and ruptured-aneurysm bleeding, where a protocol includes whole blood. The evidence is thinner than in trauma. Use depends on the protocol.

ED / ICU / Transport

• Massive transfusion protocol (MTP) product: at hospitals that stock LTOWB, it is one balanced unit. The single-center pediatric MTP series is covered under Special Populations.
• Blood-on-board and interfacility transport: Canadian critical care transport programs carry blood on board. For rural and remote transport, where plasma logistics are hard, the 2025 Canadian consensus lists whole blood as an option.

Other Uses

• Neonates and infants: the only reports are small case series. Use specialist neonatal transfusion protocols only.

Doses vary by protocol; follow local protocols and medical direction.

Available Forms

• Low-titer group O whole blood (LTOWB): one unit of about 450–600 mL, per the AABB POHT reference standard 5.1.9A as summarized in the 2026 Prehospital Blood Transfusion Coalition (PBTC) framework. Anti-A and anti-B titers are typically below 256, and the supplier sets that threshold. Expect most units to be RhD-positive.
• Expiry: 21 days with CPD/CP2D or 35 days with CPDA-1 anticoagulant. Check the unit label.

Adult Dosing

Pediatric Dosing

Preparation & Administration

• Identification: two identifiers, ABO and RhD on the tag, unit number and expiry at pick-up and at the bedside. Read the unit label; do not assume a low-titer status.
• Warming: an in-line warmer validated for blood, used per device labeling. Don't skip it. The 2025 Canadian consensus calls in-line warmers and warming measures essential.
• Sample: draw a pre-transfusion sample for the blood bank if it does not delay the first unit, per protocol. Donor cells and plasma can confound recipient ABO typing and antibody screening after group O whole blood.
• Line: large-bore IV or IO. Use a dedicated set with the filter your blood supplier specifies. Keep calcium, vasopressors and hypotonic fluids off the blood line.
• Pressure infusion: use pressure infusers per device and program labeling; pediatric volume delivery is protocol-specific.
• Flush: 0.9% sodium chloride only.
• IO: IO route per protocol; see the IO Access page.

Contraindications

• No absolute contraindication in life-threatening hemorrhage: the 2025 NAEMSP position and the PBTC framework both state it, when a protocol applies.
• Refusal: document it, religious refusal included, per protocol. Under the emergency doctrine, the PBTC framework asks programs to respect religious autonomy.
• RhD-positive unit to an RhD-negative female of reproductive potential (relative): prefer RhD-negative product when it is available. When it is not, and transfusion is needed, do not hold back RhD-positive product (see Special Populations).

Precautions

• RhD alloimmunization: reported anti-D rates after trauma transfusion run from about 8% to 43%. The modeled risk of severe hemolytic disease of the fetus and newborn (HDFN) or perinatal death is about 0.24% after an RhD-positive exposure (joint position statement 2026). Plan on blood bank follow-up.
• Titer and ABO: group O whole blood suits non-O recipients only if the unit meets the supplier's low-titer threshold. Thresholds vary. One pediatric program used below 200, and the PBTC framework lists typical values below 256.
• Transfusion-associated circulatory overload (TACO): the risk runs higher with heart, lung or kidney disease, and in the very young and in older adults. A 450–600 mL unit is a lot of volume for a small patient.
• Hypocalcemia and hypothermia: citrate binds calcium. Rapid, large volumes without warming pull body temperature down.
• Children: weight-based volume and age-adjusted vital sign thresholds (PBTC framework).

Hold / Reassess If

• Signs of a transfusion reaction (fever, rigors, hypotension, hemoglobinuria or dark urine, oozing): stop, keep the line open with 0.9% sodium chloride, notify the blood bank.
• New dyspnea, falling SpO₂, crackles or rising work of breathing: slow or stop, and assess for TACO or TRALI.
• Ionized calcium below 0.9 mmol/L, or signs of hypocalcemia: give calcium now (Calcium Chloride page).
• Falling temperature: warm the product and the patient.

Common

• Hypocalcemia from citrate during rapid or large-volume transfusion.
• Hypothermia with rapid large volumes given without warming.
• Mild febrile or allergic reactions (including urticaria). The sources reviewed do not quantify how often these happen.
• Volume overload in patients with limited cardiac or renal reserve.

Serious / Life-Threatening

Overdose & Toxicity Management

• Reaction workup: send the bag and tubing to the blood bank with a post-reaction sample. Report concerns to the treating physician and the EMS medical director, who contacts the supplying blood bank.
• Citrate hypocalcemia: calcium chloride 1 g IV or calcium gluconate 3 g IV, guided by ionized calcium (see the Calcium Chloride page for targets and dosing).
• Hypothermia: warm the product and patient with an in-line warmer and active rewarming.
• Anaphylaxis: epinephrine IM per protocol; airway support and fluids.

Clinically Significant Interactions

IV Compatibility

• Diluent: none. Give the unit as supplied.
• Flush: 0.9% sodium chloride only.
• Dedicated line: keep calcium, vasopressors, TXA and hypotonic fluids off the blood line.
• Verify with an institutional compatibility resource.

• Pediatrics: weight-based volume of 10–20 mL/kg (PBTC framework); see the Pediatric Dosing table. In a single-center MTP series of 16 children, 24-hour mortality was 25% and acute kidney injury occurred in 63%. The numbers are small. Monitor kidney function and potassium.
• Neonates: the evidence is small case series only. Use specialist neonatal protocol and medical direction.
• Pregnancy: follow obstetric and medical direction. Do not hold back indicated hemorrhage treatment. The blood bank plans the anti-D follow-up after an RhD-positive exposure (see the Rho(D) Immune Globulin page).
• Lactation: the sources reviewed establish no specific adjustment.
• Reproductive-potential females: prefer RhD-negative product when available. Do not hold back life-saving transfusion. Females of childbearing potential with trauma are about 40% less likely than males to receive LTOWB (joint position statement 2026).
• Older Adults: TACO risk is higher. Reassess after each unit.
• Renal Impairment: no dose adjustment is established. Volume tolerance and TACO are the main concerns. Kidney injury was common in the pediatric series.
• Hepatic Impairment: the sources reviewed establish no specific adjustment.
• Obesity / Dosing Weight: adult doses run by units, with no weight adjustment. Pediatric doses use actual weight.

• Scope: EMS and critical care transport programs that run a blood program. Expect scope and product choice to vary by state and agency protocol.
• Storage & Stability: 1–6 °C in storage and 1–10 °C in transport (AABB POHT 5.1.9A, as summarized by PBTC). Use validated containers and continuous temperature monitoring, with recordings at least every 4 hours (standard 5.1.9.3). Validate the container against the longest transport you expect.
• Carried Concentration: not applicable. Confirm the unit number, ABO and RhD on the tag, and expiry at pick-up and handoff.
• Infusions in Transport: pressure infuser and in-line warmer per program. Dedicated line; verify product and unit number at handoff.
• Altitude / Environment: keep product in the validated cooler; avoid freezing and heat exposure of the cooler.
• Handoff Essentials: unit numbers, volume, start and stop times, pre- and post-transfusion vitals, any reaction, calcium given and the time, and the blood bank contact.

Mechanism of Action

• Red cells carry oxygen. That restores delivery to tissues and reverses shock physiology.
• Plasma clotting factors and platelets arrive in one unit, in physiologic ratio. That gives hemostatic support without separate components. Platelet function is debated for stored product (editorial, BJA 2026).
• Volume: each unit restores intravascular volume, at 450–600 mL per unit.
• Citrate anticoagulant binds ionized calcium. Rapid transfusion then leads to hypocalcemia.

Pharmacokinetics

• Metabolism and elimination: not applicable. This is a biologic product. The recipient's own cells and proteins handle its components.

Generic Name

Low-titer group O whole blood (LTOWB); also written low-titer O-positive whole blood (LTO+WB)

Brand Names

None (blood product; supplied by a licensed blood establishment)

Pharmacologic Class

Allogeneic blood product (whole blood)

Therapeutic Class

Hemostatic resuscitation; oxygen-carrying and volume replacement

Controlled Substance

Not controlled

ISMP High-Alert

No (not verified against the ISMP list; see editorFlags)

Look-Alike / Sound-Alike

None commonly reported

Error-Prone Abbreviations to Avoid

"U" for units (write "units"); "O+" vs "O−" (write RhD-positive or RhD-negative)