11. Blood products and blood substitutes

1. Definition

• Blood components → parts of donated whole blood separated by centrifugation
• Blood products (plasma derivatives) → industrially fractionated from pooled plasma
• Blood substitutes → solutions that replace volume or carry oxygen without donor blood
• Principle → give only the component the patient lacks

2. Classification

A. Cellular components

• Packed red cells → anaemia, acute blood loss
  • Volume about 280 mL; haematocrit 0.55–0.65
  • Stored at 2–6 °C for up to 35–42 days
  • 1 unit → raises haemoglobin by about 10 g/L in an adult
• Leucocyte-depleted red cells → fewer febrile reactions, less cytomegalovirus transmission
• Washed red cells → IgA deficiency, recurrent allergic reactions
• Irradiated components → prevent transfusion-associated graft-versus-host disease (immunosuppressed, Hodgkin's lymphoma, intrauterine transfusion)
• Platelets → thrombocytopenia, platelet dysfunction
  • Stored at 20–24 °C with agitation for 5–7 days
  • Highest risk of bacterial contamination
  • Thresholds: bleeding < 50 × 10^9/L; prophylaxis < 10 × 10^9/L; neurosurgery < 100 × 10^9/L
• Granulocytes → rarely; neutropenic sepsis

B. Plasma components

• Fresh frozen plasma (FFP) → all coagulation factors
  • Frozen within hours of donation, stored at −25 °C
  • Dose → 12–15 mL/kg
  • Indications → coagulopathy with bleeding, massive transfusion, disseminated intravascular coagulation (DIC)
  • Must be ABO compatible
• Cryoprecipitate → fibrinogen, factor VIII, von Willebrand factor, factor XIII
  • Indication → fibrinogen < 1.5 g/L with bleeding

C. Plasma derivatives

• Albumin 4.5% and 20% → hypoalbuminaemia, paracentesis of ascites, burns
• Prothrombin complex concentrate (PCC) → factors II, VII, IX, X; urgent warfarin reversal
• Factor VIII and IX concentrates → haemophilia A and B
• Fibrinogen concentrate
• Recombinant factor VIIa → life-threatening bleeding resistant to other treatment
• Immunoglobulins → anti-D, hepatitis B, tetanus, rabies, intravenous immunoglobulin

D. Blood substitutes: volume replacement

• Crystalloids → first choice for resuscitation
  • 0.9% sodium chloride → hyperchloraemic acidosis in large volumes
  • Balanced solutions → Hartmann's (Ringer's lactate), Plasma-Lyte
  • 5% glucose → maintenance water; not for resuscitation
  • Only about 25% stays in the circulation
• Colloids → stay longer in the circulation
  • Albumin
  • Gelatins (Gelofusine) → anaphylaxis risk
  • Dextrans → impair platelets, anaphylaxis
  • Hydroxyethyl starch → kidney injury, coagulopathy; avoided in sepsis and critical illness
• Hypertonic saline → head injury, small volume resuscitation

E. Oxygen-carrying substitutes

• Haemoglobin-based oxygen carriers
• Perfluorocarbons
• Experimental, not in routine use

3. Alternatives to donor blood

• Preoperative anaemia correction → oral or intravenous iron
• Intraoperative cell salvage → shed blood washed and returned; not in bowel contamination or malignancy (relative)
• Acute normovolaemic haemodilution
• Preoperative autologous donation
• Tranexamic acid
• Erythropoietin
• Patient blood management → restrictive transfusion thresholds

4. Clinical and surgical significance

• Massive haemorrhage protocol → red cells, FFP and platelets in ratio about 1:1:1
• Add cryoprecipitate when fibrinogen < 1.5 g/L
• Give calcium → citrate in products binds calcium
• Jehovah's Witnesses → refuse whole blood and main components; may accept cell salvage, albumin, some factor concentrates