Blood plasma: composition, function, and medical uses

Composition and characteristics

By volume, plasma is mostly water, and the dissolved content gives it specific physiological roles. It contains a complex mix of proteins (including albumin and transport proteins), dissolved glucose, mineral and ionic electrolytes, a range of hormones, metabolic waste such as carbon dioxide (largely as bicarbonate), and clotting factors needed to maintain haemostasis. Plasma is the primary transport medium for many substances and contributes to the regulation of blood pressure, pH and osmotic balance. It also plays a role in immunity through antibodies and complement proteins.

Clinical preparation and blood products

When blood is collected for laboratory analysis or transfusion, an anti-coagulant is often added to prevent clotting. The sample is then separated by a centrifuge, which drives the denser blood cells to the bottom and leaves plasma as the supernatant. Separated plasma can be transfused directly or processed into derived products. Distinct blood products used in medical care include saline for volume replacement, packed red cells for restoring oxygen-carrying capacity, whole blood when all components are needed, and plasma transfusions for clotting factor replacement.

Plasma versus serum and therapeutic techniques

Plasma differs from serum in that plasma still contains clotting proteins; serum is the fluid left after blood has clotted and therefore lacks fibrinogen and other clotting factors. A common way to define this distinction is that plasma includes fibrinogen, whereas fibrinogen is absent from serum. Medical procedures that manipulate plasma include plasmapheresis — removal, treatment, and return of plasma — and plasma exchange for certain autoimmune or inflammatory disorders. Donated plasma can also be pooled and fractionated to produce specific therapies such as immunoglobulins and clotting factor concentrates.

History, usage and important notes

The use of plasma in medicine expanded during the 20th century as techniques for safe collection, storage and screening improved. Plasma is essential in emergency care for treating massive bleeding and in correcting coagulopathies. It is also used diagnostically; analysis of plasma components provides information about organ function, coagulation status and metabolic balance. Handling and transfusion of plasma must follow strict safety protocols to reduce infectious risk and ensure compatibility.

Further reading and resources

• Appearance and basic definition
• Relation to blood cells
• Role in excretion and waste transport
• Carbon dioxide transport
• Transport functions
• Hormones in plasma
• Anticoagulants used in collection
• Centrifugation and processing
• Plasma proportion of blood
• Protein components
• Glucose and metabolites
• Minerals and ions
• Electrolyte balance
• Fibrinogen and clotting distinction
• Physical properties
• Context within whole blood

For clinical decisions and detailed protocols, consult specialist resources or clinical guidelines rather than this summary. Additional reputable references are available through medical libraries and authoritative health organizations.