Blood transfusion

From Ganfyd

Historical Aspects

See History of blood transfusion

Blood components

• Donation & processing

Red cells

Given as red cell concentrate or synonymously packed red cells. 1 unit raises haemoglobin by approximately 1g/dL.

Calculations based on ~450ml±10% of whole blood is added to 63ml anti-coagulant and processed to remove plasma leaving a volume of 280±60 ml with a haematocrit of approximately 50-70% and therefore a total haemoglobin of about 40-70g/unit (>40g according to standard).^[1]

Indications

There is considerable controversy, but most are agreed that with the known physiology in health and disease, the potential risks of blood transfusion mean that the "10/30" rule (Hb> 10g/dl and haematocrit > 30% before operation) that formerly applied makes little sense as does a "transfusion trigger" of 10g/dl. In health humans the optimal haematocrit is about 35%^[2] although flow through small vessels may be optimal at higher values with some variation with say neonates compared to adults^[3].

Operations

The published evidence base is inconclusive but consistent with Hb about 8g/dl not being associated with harm.

Intensive care

• 30-day mortality was 23% in ITU patients maintained at Hb 10-12g/l and 19% for those maintained at Hb 7-9 g/dl with a significant reduction in heart failure in the later group.^[4]. Trends in this and other studies are towards better long term mortality and less myocardial infarction, as well as a 40-50% drop in tranfusion requirement in either adults or children^[5] for Hb in the 7-9g/dl range.

Chronic anaemia

Fatigue, weakness dizziness and reduced exercise tolerance in the context of anaemia that do not reduce meaningful patient function do not justify transfusion. In severe anaemia in children with malaria those whose Hb was kept above 4 g/dl did much better^[6]. In thalaesemma and sickle cell disease, 9-10g/dl seem optimal^[7].

Cardiovascular disease

Multiple studies show inconsistent correlation with degree of anaemia down to 8 g/dl and haemocrit lower than 33% improved outcome in one large study of myocardial infarction^[8].

Platelets

Can be produced by:

1. Platelet rich plasma (PPP) with >60 x10⁹ in ≥ 75% units^[9]
2. Buffy-coat (BC) with >60 x10⁹ in ≥ 75% units^[9]
3. Apheresis with >200 x10⁹ in ≥ 90% units^[9]

Indications

General guidance to be adjusted for individual adult patient circumstances is^[10]:

• platelet count ≤ 10,000/µl in blood dyscrasia or malignancy if patient stable
• platelet count ≤ 20,000/µl in major haemorrhage or other high risk situations such as fever, rapidly decreasing platelet count or sepsis
• platelet count ≤ 50,000/µl prior to major surgery
• platelet count ≤ 100,000/µl prior to neurosurgery

Exceptions to this are likely to apply with CABG, TTP, HIT, ITP where platelet transfusion is either ineffective or dangerous and neonates where special precautions and criteria apply.

• For dose use local guidance as no consensus but usually about 50-100 x10⁹ platelets/10kg

Freshly Frozen Plasma

Indications

• These might vary due to the availability of more specific blood products. Generally recombinant factor VIIa is used now in haemophilia.
• Reversal oral anticoagulants.

Cryopreciptate

Indications

These might vary due to the availability of more specific blood products. Von Willebrand's disease is usually now treated with pdFVIII products enriched with von Willebrand factor.

Risks

Because the potential for extreme harm and even death from blood transfusion exists an audit scheme via the national body called Serious Hazards of Transfusion is in place.

• Labelling errors
• From delivery systems
  • cannula site infection, air embolus, haematoma
• Fluid overload
• Transfusion reactions
  • Fever, shortness of breath, shivers, chest pain, back pain, rash
• anaphylaxis
• transfusion related acute lung injury (TRALI)
• transmission of infection (estimated at 1 in 2 million transfused units in UK for HIV infection)
• suppression of immune response
• iron overload

External Links

References