Fundamentals of Pharmacology for Veterinary Technicians

1. Fundamentals of Pharmacology for Veterinary Technicians Chapter 19 Fluid Therapy and Emergency Drugs © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

2. Basics of Body Fluid • Water is the primary body fluid • Body water is distributed among three types of compartments: intracellular, intravascular, and interstitial • Intracellular fluid (ICF) = fluid within the cell (two-thirds of body water) • Extracellular fluid (ECF) = fluid within the blood vessels and in the tissue spaces between the blood vessels and cells (one-third of body fluid) © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

3. Basics of Body Fluid • Body water contains solutes (substances that dissolve in solvent; particles) • Electrolytes are substances that split into ions when placed in water • Primary ions in the body are sodium, potassium, chloride, phosphate, and bicarbonate • Cations are positively charged ions • Anions are negatively charged ions • Body water is the solvent in biological systems • To establish equilibrium, body water moves along its concentration gradient © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

4. Basics of Body Fluid • Extracellular fluid shifts between the intravascular space (blood vessels) and the interstitial space (tissues) to maintain a fluid balance with the ECF compartment • Fluid exchange occurs only across the capillary walls • Fluid therapy in animals may involve the use of crystalloids and/or colloids • Crystalloids are diffusible substances that dissolve in solution • Colloids are nondiffusible substances © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

5. Fluid Therapy • The basis for fluid therapy depends on the animal’s hydration status (see Table 19-1) • Fluid therapy can replace water, sodium, potassium, and chloride electrolytes, and restore hydrogen ion balance (pH balance) © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

6. Routes of Fluid Administration © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

7. Routes of Fluid Administration © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

8. Routes of Fluid Administration © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

9. Tonicity of Fluids • Tonicity refers to the osmotic pressure of a solution based on the number of particles per kilogram of solution (osmolality) • An isotonic solution has the same osmotic pressure as blood and extracellular water • A hypotonic solution has osmolality lower than that of blood; RBCs can swell • A hypertonic solution has osmolality higher than that of blood; RBCs can shrink © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

10. Types of Crystalloids • Isotonic • 0.9% sodium chloride (normal saline) • Lactated Ringer’s solution • Normosol • Plasmalyte • Hypotonic • 5% dextrose in water (D5W) • ¼ NS (0.25% normal saline) • ½ NS (0.45% normal saline) • Hypertonic • 0.9% normal saline with 5% dextrose • 10% dextrose in water • 3% normal saline © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

11. Types of Colloids • Colloid solutions are fluids with large molecules that enhance the oncotic force of blood, causing fluid to move from the interstitial and intracellular spaces into the vascular space • Natural • Plasma • Albumin • Whole blood • Synthetic • Dextrans • Hydroxyethyl starch • Oxypolygelatin © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

12. Fluid Additives • Special additives can be supplemented to crystalloid solutions • When administering additives, it is important to remember to withdraw and discard an amount of fluid equal to the amount of additive being supplemented • Types of additives: • 50% dextrose • Potassium • Sodium bicarbonate • Calcium • Vitamins © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

13. Calculating Fluid Volumes • Must consider that animals require fluids for the following: • Rehydration • Maintenance • Ongoing fluid loss • Make sure the units of measure are the same when performing these calculations • Make sure the volumes make sense; we don’t give 1,000 liters to a 4-pound cat © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

14. Example: An adult 14-lb cat with 3% dehydration comes into the clinic. It is estimated that the cat vomited 100 ml of fluid overnight Maintenance fluid is the volume of fluid needed daily to maintain body function Maintenance fluids can be dosed at 50 ml/kg/day in adults and 110 ml/kg/day in young animals Step 1: Convert 14 lb to kg using the conversion factor 2.2 lb = 1 kg 14 lb x 2.2 lb/kg = 6.4 kg Step 2: Calculate maintenance volume 6.4 kg x 50 ml/kg/day = 318 ml per day Calculating Fluid Volume © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

15. Example: An adult 14-lb cat with 3% dehydration comes into the clinic. It is estimated that the cat vomited 100 ml of fluid overnight Rehydration fluid is based on the estimated percent of dehydration % dehydration x weight in kg = deficit in liters Step 1: Convert 14 lb to kg using the conversion factor 2.2 lb = 1 kg 14 lb x 2.2 lb/kg = 6.4 kg Step 2: Calculate replacement for dehydration 3% = 0.03 0.03 x 6.4 kg = 0.192 l 0.192 l x 1,000 ml/l = 192 ml 192 ml x 0.8 (80% of dehydration value replaced in 24 hours) = 154 ml to replace on first day Calculating Fluid Volume © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

16. Example: An adult 14-lb cat with 3% dehydration comes into the clinic. It is estimated that the cat vomited 100 ml of fluid overnight Ongoing fluid loss is an estimation based on the additional loss of fluid due to vomiting or diarrhea Take estimated volume Step 1: Take estimated volume lost in fluid and add to the other volumes Final step: Take all values and add together 318 ml + 154 ml + 100 ml = 572 ml Calculating Fluid Volume © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

17. How and How QuicklyIs It Given? • Rate of fluid replacement parallels the severity of dehydration • Ideally, fluids are given over a 24-hour period • Fluids are stored and given by fluid bags or bottles attached to administration sets • Fluids are administered with either: • An adult administration set that delivers 15 gtt/ml (usually) • A pediatric administration set that delivers 60 gtt/ml (usually) • See text and “Fluid & Electrolytes for Veterinary Technicians” CD for sample calculations © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

18. Emergency Drugs • In an emergency situation, it is important to remember basic life support • A = airway = establish a patent airway (endotracheal tube, suctioning, tracheostomy) • B = breathing = provide oxygen to the patient by providing airway or mechanical ventilation • C = circulation = get blood moving, either by manual manipulation of the heart or by the use of drugs • See Table 19-3 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.