Plasma

Plasma is the liquid component of blood and contains over a thousand different proteins. It consists mainly of water, but also of important proteins, electrolytes, nutrients and waste products. Plasma transports nutrients, hormones, enzymes and other substances through the body. In veterinary medicine, plasma is transfused primarily for coagulation disorders.

Composition of Plasma

Plasma consists of several components that perform different functions in the dog’s body:

1. Water: Serves as a solvent for the other components and helps transport nutrients, gases and waste products.
2. Plasma proteins: These are divided into albumin and globulins, with albumin making up around half of the total protein.
   • Albumin: Plasma proteins fulfil several tasks, including maintaining colloid osmotic pressure, transporting substances and blood coagulation; albumin makes up around half of the total protein.
   • Globulins: These include immunoglobulins, which play an important role in the immune system, as well as proteins involved in the transport of lipids and metals.
   • Fibrinogen: It is present in plasma but not in serum, accounting for the difference in total protein there.
3. Electrolytes: These include sodium, potassium, calcium, chloride and bicarbonate, which are necessary for maintaining acid-base balance, nerve function and muscle function.
4. Nutrients: Glucose, amino acids, fatty acids and vitamins, which are transported via the plasma to the body’s cells.
5. Waste products: Carbon dioxide, urea and creatinine are waste products of cellular metabolism that are transported via the plasma to the excretory organs (such as kidneys and lungs).

Functions of Plasma in Dogs

Plasma performs many functions that are crucial for the dog’s health:

1. Transport function: Plasma transports nutrients, hormones, enzymes and oxygen to the body’s cells while simultaneously conveying waste products and carbon dioxide to the organs responsible for their excretion.
2. Blood clotting: Plasma contains fibrinogen, which is responsible for blood clotting. In the event of an injury, fibrinogen is converted into fibrin to form a blood clot and stop bleeding.
3. Maintenance of blood pressure: The proteins contained in plasma, particularly albumin, help maintain osmotic pressure, which is responsible for fluid balance in the blood and tissues. This prevents fluid from leaking out of blood vessels into surrounding tissue and causing swelling.
4. Immune defence: Plasma contains antibodies (immunoglobulins) responsible for defending the body against infections. These antibodies recognise and neutralise pathogens such as bacteria and viruses.

Use of Plasma in Veterinary Medicine

In veterinary medicine, plasma is frequently used therapeutically to support dogs with certain conditions or after severe injuries. Some of the most common applications include:

1. Plasma transfusions: Fresh frozen plasma replaces lost clotting factors; the dose is based on body weight and determined by the vet.
2. Treatment of clotting disorders: In dogs suffering from clotting disorders, such as von Willebrand disease or after ingestion of rat poison that inhibits blood clotting, plasma transfusions can be used to replace clotting factors and stop bleeding.
3. No substitute for protein deficiency: According to the MSD Veterinary Manual, plasma is not effective for correcting low blood protein; however, in cases of clotting disorders, it replaces the missing clotting factors.