Transfusion in Critical Illness and Cardiac Disease

Critically ill patients are anaemic from inflammation, haemodilution, repeated blood sampling and blood loss, and they are among the most transfused patients in hospital. Evidence shows that a restrictive red cell threshold is safe in most critically ill adults, but patients with active myocardial ischaemia, brain injury and cardiac surgery need individual decisions. The same patients are at high risk of circulatory overload and lung injury, so every unit must have a reason.

Principle. Transfuse for inadequate oxygen delivery or bleeding, not for a haemoglobin number alone, and give one unit at a time with reassessment.

Risk context. Transfusion associated circulatory overload, transfusion related acute lung injury, infection, immunomodulation and, in cardiac surgery, bleeding from heparin, bypass and platelet dysfunction. Fresher red cells have not been shown to give better outcomes than older stored units in these patients, so age of unit is not a reason to delay.

Special groups. Older adults, patients with heart failure or renal failure, sepsis, acute respiratory distress syndrome, extracorporeal support, traumatic brain injury and subarachnoid haemorrhage, and patients refusing blood. In East Africa, intensive care and cardiac surgery capacity is concentrated in a few centres and blood stock for complex cases is limited, so avoidance of unnecessary transfusion matters.

Red cell thresholds, with the circumstances in which they apply.

Assess oxygen delivery. Chest pain or ischaemic electrocardiogram changes with troponin rise, new arrhythmia, hypotension unresponsive to volume, lactate rising, low central venous oxygen saturation (an imperfect guide), and cardiac output in selected patients.

Haemostatic thresholds.

• Platelets: prophylaxis under 10 x 10⁹/L (under 20 x 10⁹/L with sepsis or high bleeding risk), over 50 x 10⁹/L for bleeding or procedures, and over 100 x 10⁹/L in brain injury.

• Plasma: for bleeding with prolonged clotting times, and not for abnormal coagulation tests without bleeding.

• Fibrinogen: replace under 1.5 g/L with bleeding (higher in some cardiac surgery settings by local practice).

Cardiac surgery bleeding. Distinguish surgical bleeding from coagulopathy using viscoelastic testing or laboratory results, correct heparin effect (protamine), temperature and calcium, and replace fibrinogen, platelets and factors as results direct.

Differential considerations. Haemodilution, haemolysis from devices, occult bleeding (retroperitoneal, gastrointestinal), marrow suppression, nutritional deficiency and renal anaemia.

Red flags. Falling haemoglobin with haemodynamic instability, ongoing chest pain with ischaemic changes, chest drain output over about 200 mL/hour, and rising lactate.

Critical illness.

1. Reduce blood loss: use small volume tubes, close sampling systems and only necessary tests.

2. Treat the cause of anaemia, and give iron for deficiency (intravenous iron when oral is unsuitable).

3. Transfuse one unit at a time at the threshold and reassess.

4. Run each unit over 2 to 4 hours (about 1 mL/kg/hour in overload risk), with a diuretic only when there are signs of overload.

Acute myocardial infarction. Decide with the cardiologist. Consider transfusion when haemoglobin is under 8 g/dL with ongoing ischaemia, and a higher threshold up to 10 g/dL may be considered, with single units, slow rate and close monitoring for overload and pulmonary oedema. Avoid transfusion for stable patients with a mildly low haemoglobin.

Cardiac surgery.

• Before surgery: screen and treat anaemia (iron, vitamin B12, folate, erythropoiesis stimulating agents), stop antiplatelet and anticoagulant drugs as the surgical plan allows.

• During surgery: cell salvage, tranexamic acid (doses differ by unit, with high doses linked to seizures, so use the lowest effective dose), meticulous haemostasis, normothermia, and viscoelastic testing where available. Accept a lower haemoglobin on bypass unless there is ischaemia.

• After surgery: threshold about 7.5 g/dL, with platelets, fibrinogen and plasma only for bleeding or measured deficiency, and no prophylactic plasma.

Extracorporeal support. Thresholds about 7 to 8 g/dL, with a focus on bleeding, anticoagulation targets and platelet counts.

Special groups.

• Heart failure and older adults: slow rates, small volumes and close monitoring.

• Brain injury: avoid hypoxia and hypotension, and platelets over 100 x 10⁹/L with bleeding.

• Patients refusing blood: pre-optimisation, cell salvage and tranexamic acid.

Monitoring. Haemodynamics, oxygen saturation, fluid balance, electrocardiogram, lactate and haemoglobin after transfusion. During transfusion, watch for dyspnoea and oxygen requirement.

Complications. Circulatory overload, lung injury, febrile and allergic reactions, infection, thrombosis and, with older units in massive volumes, hyperkalaemia.

Referral and escalation. Cardiology, cardiac surgery, intensive care and haematology early. Blood bank medical staff for complex product needs.

Disposition. Record the threshold and reason for each unit, and plan iron and treatment of the cause of anaemia before discharge to prevent repeated transfusion.