Red Cell Transfusion Thresholds

A restrictive strategy transfuses red cells only when haemoglobin falls under a lower threshold, usually 7 to 8 g/dL, and a liberal strategy uses a higher threshold, usually 9 to 10 g/dL. In most stable hospitalised adults, the restrictive approach gives outcomes at least as good as the liberal approach with fewer units used. These thresholds are not triggers in uncontrolled major haemorrhage, where haemoglobin lags behind blood loss.

Principle. The threshold is a point at which to assess the patient, not an automatic order. Symptoms, haemodynamics, comorbidity and speed of decline all modify the decision.

Risk context. Liberal transfusion exposes patients to more units and more risk of overload, infection and reactions. Restrictive transfusion risks under-treating patients with limited tolerance of anaemia, especially those with myocardial ischaemia or brain injury.

Special groups. Cardiac disease, acute coronary syndromes, neurological injury, haemoglobinopathies, oncology, neonates and children, pregnancy and the older adult each have different considerations.

Usual adult thresholds, with the circumstances in which they apply.

Assess before applying a number. Look for chest pain, dyspnoea, syncope, heart failure, ischaemic electrocardiogram changes, hypotension, tachycardia unresponsive to volume, raised lactate and low central venous oxygen saturation.

Where thresholds do not apply. Uncontrolled haemorrhage, haemodynamic instability, rapidly falling haemoglobin, and acute myocardial infarction with ongoing ischaemia.

Children in malaria endemic regions. Severe anaemia with haemoglobin under 4 g/dL, or under 6 g/dL with respiratory distress, shock, impaired consciousness or very high parasitaemia, is a usual indication.

Differential considerations. Haemodilution after fluids, haemolysis, chronic compensated anaemia and spurious laboratory values.

Restrictive plan.

1. Measure haemoglobin and assess symptoms.

2. If at or over the threshold and stable, do not transfuse; treat the cause.

3. If under the threshold, transfuse one unit and reassess clinically and with haemoglobin.

4. Repeat only if the threshold is still crossed or symptoms persist.

Liberal plan. Considered for selected patients with acute coronary ischaemia, severe symptoms or neurological injury, always with a named target and a stop point.

Dose and rate. A single unit of red cells over 2 to 4 hours, slower (about 1 mL/kg/hour) in patients at risk of overload.

Special groups.

• Cardiac and older adults: single units, slower rate, close monitoring for overload.

• Neonates and children: thresholds depend on gestation, postnatal age, respiratory support and symptoms, and are applied by weight based dosing.

• Pregnancy: severe anaemia near term may need correction before delivery.

• Sickle cell disease: avoid overshooting haemoglobin over 10 g/dL because of hyperviscosity.

• Oncology: balance infection and bleeding risks, and use irradiated components where indicated.

Monitoring. Haemoglobin at about 1 hour after completion for non-bleeding patients, and symptoms and vital signs throughout.

Complications. Overload, reactions, hyperkalaemia in small infants and rapid massive transfusion, and delayed haemolysis.

Referral and escalation. Early haematology input for transfusion requirement without a cause, for patients refusing blood, and for refractory anaemia. Cardiology input when ischaemia and anaemia coexist.

Disposition. Document the threshold used and the reasons for deviating from it. Plan iron, vitamin B12, folate, malaria treatment and other causes so that further transfusion is avoided.