ANSWERS

1. What are the 4 main reasons for fluid therapy?
   • Replacement of dehydration deficits.
   • Maintenance of normal hydration.
   • Replacement of essential electrolytes and nutrients.
   • To act as a carrier for certain intravenous drugs.
2. Define shock.
   A condition whereby severe impairment of capillary perfusion results in deterioration of cell function; blood flow is insufficient to provide adequate oxygen and nutrients and to remove waste products. Fluid therapy is an essential part of the treatment of shocked animals.
3. What percentage of the adult body weight of an animal is water?
   60%.
4. Why is the average water content of young animals higher than that of adults?
   Young animals are less able to produce concentrated urine. This emphasises the need to perform prompt fluid therapy in neonates.
5. Which hormone is responsible for the control of urine concentration?
   Antidiuretic hormone (ADH). This hormone is also known as vasopressin.
6. Where is antidiuretic hormone stored?
   ADH is stored in the posterior pituitary.
7. When water intake is decreased, or when increased fluid loss occurs, what 2 events take place?
   • Thirst centres within the hypothalamus are stimulated.
   • Osmoreceptors, which detect the rise in plasma osmotic concentration, stimulate the release of ADH. This promotes the reabsorption of water from the renal tubules thus increasing urine concentration.
8. What hormone is released in the event of reduced renal blood flow and why?
   Renin. This causes the production of angiotensin, which in turn stimulates the release of aldosterone from the adrenal cortex. Aldosterone acts on the kidney to increase the resorption of sodium within the distal tubule (and subsequently water); therefore urine concentration is increased.
9. Obese animals have a lower water content than animals at their optimum weight, why is this?
   Fatty tissue contains less water than lean tissue. Fluid therapy in obese animals should be based upon optimum weight rather than actual body weight to avoid overhydration.
10. What is an electrolyte?
    A substance that yields ions (small water-soluble particles of atomic or molecular size carrying one or more positive or negative charges) when dissolved in water.
11. What is a cation?
    An ion which carries one or more positive charges.
12. What is an anion?
    An ion which carries one or more negative charges.
13. Name the main cation of extracellular fluid.
    Sodium.
14. Name the main anion of extracellular fluid.
    Chloride.
15. Name the main cation of intracellular fluid.
    Potassium.
16. What is the largest fluid component of the body?
    Intracellular fluid (ICF). This makes up two thirds of the body's water content.
17. Where in the body is most intracellular fluid located?
    In skeletal muscle.
18. Extracellular fluid (ECF) makes up one third of the body's water content. What does ECF consist of?
    • Interstitial fluid (15%).
    • Plasma water (5%).
    • Transcellular water (<1%).
19. What is the function of interstitial fluid?
    This is the fluid in which the body's cells are bathed. It acts as an intermediary between the cells and the blood.
20. What is plasma water?
    The fluid portion of the blood in which the corpuscles are suspended.
21. List 10 substances contained within plasma water.
    • Water.
    • Mineral salts.
    • Plasma proteins.
    • Food.
    • Gases in solution (mostly oxyhaemoglobin).
    • Waste products (urea and creatinine).
    • Hormones.
    • Enzymes.
    • Antibodies.
    • Antitoxins.
22. Define transcellular fluid.
    A specialised fluid produced by active secretory mechanisms. Examples are cerebrospinal fluid (CSF) and gastrointestinal secretions.
23. What is a buffer solution?
    A physical or chemical system which acts to prevent change in the concentration of another chemical substance. Sodium bicarbonate is the main buffer of blood and tissue fluid.
24. What is pH?
    Per hydrogen; a measure of the hydrogen ion concentration of a solution (and therefore the acidity or alkalinity). pH is defined by scientists as the negative logarithmic expression of hydrogen ions.
25. What is acid-base balance?
    The normal ratio between acidic and alkaline (basic) ions required to maintain the pH of blood and body fluids. (The pH of blood is 7.35).
26. What is metabolic acidosis? List possible causes.
    Acid retention or alkali loss. Causes include:
    • Acid ingestion.
    • Ketoacidosis.
    • Diarrhoea (Loss of HC03-).
27. What is metabolic alkalosis?
    Acid loss or alkali retention. Causes include:
    • Alkali ingestion.
    • High dose diuretics.
    • Hyperaldosteronism.
    • Vomiting.
28. How does the body control dramatic hydrogen ion fluctuations?
    • Buffering. (Buffers are weak acids or proteins that react with acids and bases reducing the extent of pH change. They trap hydrogen ions and deliver them to the lungs or kidneys for excretion).
    • Respiratory response (removal of C02) reduces acidity.
    • Renal response (bicarbonate generated within the kidney cell acts as an extracellular buffer).
29. What are the most important intracellular buffers?
    Proteins.
30. Name the important extracellular buffers.
    • Bicarbonate.
    • Phosphate.
31. Define osmosis.
    The process by which pure solvent (water) moves from a region of low solute concentration to a region of high solute concentration through a semi-permeable membrane.
32. What is osmotic pressure?
    The pressure required to prevent the occurrence of osmosis; this is proportional to the number of ions in the solution.
33. Which blood protein is chiefly responsible for maintaining the difference between the osmotic pressure of plasma and interstitial fluid?
    Albumin. Blood pressure may force fluid out of the vascular compartment and into the interstitial fluid while the protein within the plasma pulls this fluid back into the vessels.