Blood Components and Transfusions

Whole Blood

• Blood withdrawn from humans, aseptically
• Anticoagulants used: heparin or citrate–dextrose
• Shelf Life: 48 hours (heparin), 35 days (citrate–phosphate–dextrose with adenine)
• Screened for pathogens, ABO group, Rh group
• Warmed to 37 °C before transfusion
• Used to replace blood lost due to injury or surgery

Platelets

• Resuspended in 20-50 ml of original plasma, contain at least 5.5 x 10^10 platelets/unit
• Shelf life: 72 hours
• Transfused to prevent or stop bleeding in patients with low platelet counts or functional platelet disorders

Concentrated Red Blood Cells

• Prepared from whole blood, anticoagulant and some plasma removed
• Stored at 2-8 °C (unfrozen) or below -65 °C (frozen)
• Shelf life: same as whole blood (unfrozen), 3 years (frozen)
• Administered to patients with severe anemia, sickle cell anemia, and newborns with hemolytic disease

Blood Substitutes

• Replace or maintain blood volume
• Ensure oxygen delivery to body tissues

Plasma Expanders

• Maintain blood pressure by providing vascular fluid volume

Colloidal Plasma Expanders

• Exert osmotic pressure similar to plasma protein, maintaining vascular volume and blood pressure
• Disadvantages: high cost, hypersensitivity risk

High Molecular Mass Dextrans (70, 75, 110)

• Promote short-term plasma volume expansion, preventing/treating shock due to blood loss
• 6% w/v solution exerts osmotic pressure similar to plasma proteins
• Initial dose: 500 ml to 1 liter administered intravenously
• Inhibit red blood cell aggregation, used to prevent/treat post-operative thromboembolic disorders and improve blood flow

Lower Molecular Mass Dextran 40 (40 kDa)

• Similar therapeutic effects to higher molecular mass dextrans
• Used at higher concentrations (10% w/v) to achieve the same osmotic pressure

Dextrans Limitations

• Dextrans 40 and 70 linked to acute renal failure
• Infusion can prompt severe anaphylactic shock
• Many patients have anti-dextran antibodies, even without prior dextran administration
• Prevention: small volume (10-20 ml) of low molecular mass dextran (Dextran 1) administered before higher molecular mass infusion to ‘mop up’ antibodies

Albumin

• Most abundant protein in blood
• Normal concentration: 42 g/liter, 60% of total plasma protein
• Responsible for 80% of blood's colloidal osmotic pressure, retaining fluid within blood vessels
• Also present in lymphatic system and skin
• Transports metabolites: fatty acids, amino acids, steroid hormones, heavy metals, drugs

HSA Structure

• 585 amino acid, 65.5 kDa polypeptide
• Unglycosylated
• 17 disulfide bonds stabilize 3D structure
• Synthesized and secreted by liver, gene located on chromosome 4

Albumin Therapeutic Use

• Used to increase plasma volume in patients with hypovolemia due to burns, trauma, or surgery
• Used to maintain blood pressure in shock
• Can also be used to treat ascites (fluid buildup in the abdomen) in people with cirrhosis of the liver
• May be used as a substitute for plasma in emergency situations where plasma is not available