1. Laboratory Techniques
LAT Chapter 3

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3. Injection Techniques
Injections with needles and syringes used to administer various substances
Syringe construction and sizes
Considerations for blood withdrawal
Proper disposable of needles
and syringes
Common routes of injection

4. Intramuscular Injection (IM)
IM generally given in hind legs.
Most desirable site is large muscle mass (e.g., quadricep muscle group).
Alternative site: muscles posterior to femur
Do not inject too much material.

5. Intraperitoneal Injection (IP)
Given in lower right quadrant of abdomen.
Avoid bladder and cecum.
Slight resistance may be encountered.
Aspirate prior to injection.
Yellow fluid: needle could be in bladder
Greenish fluid: needle could be in intestine or cecum
Blood: may have entered blood vessel

6. Intradermal Injection (ID)
Given into the thick dermal skin layer.
25 gauge needle typically used.
Needle directed at 20 to 30 degree angle into skin.
Only small quantity of fluid can be injected.
0.1 to 0.2 ml

7. Subcutaneous Injection
Placed in the more vascular space between skin and underlying muscle
Large area of subcutaneous tissue exposed by raising a tent of skin
Entering the injection site => + then 0 resistance
Precautions - puncture hand, inj. out other side

8. Intravenous Injection (IV)
IV access sites in common laboratory animals
Site preparation - disinfect
Use pressure to distend the vessel.
Insert needle at 30 degree angle to skin.
Removing the needle - apply pressure

9. Blood Collection Techniques
Used as aid to diagnose disease
Collection site and amount determined by species and test type.
Intravenous Technique
Technique basically same as intravenous injection

10. Blood Collection - Intraarterial
Auricular artery frequently used for blood collection in rabbit.
Artery easily visible.
Large quantities of blood can be obtained.
Same technique as intravenous
Apply pressure to artery after needle withdrawal.

11. Blood Collection - Retro-Orbital
Used for animals that do not have large veins.
Limited to rodents with large venous sinus or plexus posterior to the eye.
Animals typically under anesthesia.
Allow punctured vessel to clot and then place ophthalmic ointment into the eye.

12. Blood Collection - Saphenous
To collect small samples from rodents
Blood collected from saphenous vein into a capillary tube
Anesthesia not required
Multiple samples collected in same day

13. Blood Collection - Cardiac Puncture
Needle placed through chest wall and into heart
Withdraw blood slowly
Dangerous procedure
Must use general anesthesia
Will be fatal in some animals
Animal typically euthanized after procedure

14. Blood Collection - Tail Transection
Method used to collect of several drops of blood from mice or rats.
Method is controversial.
Justification for use may be required.
Anesthesia recommended for animals older than weaning age.

15. Blood Volume Total Blood Volume = 6% of Body Weight
Varies depending on species, age, sex, etc.
Guideline used when sampling frequently
Volume equal to no more than 1% of an animal’s body weight can be taken every two weeks
Example: 3kg rabbit = 30ml of blood

16. Gastric Intubation (Gavage)
Most often used for rodents
Gavage tube attached to hypodermic syringe
Hold animal in proper position
Insert tube at approximately 45 degree angle
Do not force tube
Withdraw and start again if resistance is met while inserting the tube

17. Gastric Intubation (Gavage) (cont.)
Commonly used in larger animals.
Use gag to prevent chewing of tube.
Slight resistance may be encountered when inserting tube.
Avoid entry into the trachea; delivery into lungs will likely cause death.
Guinea pig and chinchilla - palatal ostium

18. Additional Reading
1. Crow, S.E. and Walshaw, S.O. Management of Clinical Procedures in the Dog and Cat. 2nd. Edition. Lippincott-Raven. New York, NY, 1997.
2. McCurnin, D.M. Clinical Textbook for Veterinary Technicians. 3rd Edition. W.B. Saunders. Philadelphia, PA, 1994.