APSC 4464 Test 1

routes of enteral administration

in food, in water, by mouth, by oral gavage

direct oral dosing

requires restraint - may be stressful to animal; if liquid is unpalatable, may be rejected/spit out, poses risk of aspiration into trachea and lungs

routes of parenteral administration

dermal/topical, inhalation, injections

injection types

IM, SC, IP, IV, intracardiac, intranasal

steps in performing oral gavage in rodents

measure from corner of mouth to last rib for proper length/depth of insertion, restrain the animal, using needle push back on hard palate to rock head back so that passage is straight, ensure that maximum recommended volume not exceeded

variables/concerns related to whole-body inhalation versus nose-only exposure

whole body: besides being inhaled, also deposits on fur and skin, and can then be ingested orally – thus greater dose than originally calculated; nose only: limits to just inhaled dose

use of a luer-lock syringe over a standard syringe

with thick liquids, pressure may build when pushing plunger, and needle may shoot off; with a luer-lock syringe, the needle is screwed on and won’t fly off

standard convention for identifying needle diameter

lower number, larger guage (diameter); higher number, smaller guage

standard needle sizes

rodents: 23-27 guage; rabbits: 23 guage

re-using needles

tissue trauma, contamination, pain

why commercially manufactured (USP) drugs are better than non-pharmaceutical grade agents

purity, sterility, acid-base balance, longer storage/shelf life, absence of pyrogens (produced by bacterial contaminants)

common injection sites in rodents

IM (thigh muscles of hind limbs), SC (over the back), IP (ventral abdomen - near midline of upper portion of lower two quadrants), IV (lateral tail veins of rats and mice)

common injection sites in rabbits

IM (thigh muscles of hind limbs; epaxial muscles which parallel the spine), IP (ventral abdomen), SC (over the back), IV (marginal ear vein)

oral gavage and intubation maximum volume

5-20 mL/kg

mouse IM injection (mL)

< 0.05

hamster IM injection (mL)

< 0.1

rat IM injection (mL)

< 0.3

mice SC injection (mL)

< 1

rats SC injection (mL)

< 2

mice IP injection (mL)

< 1.5

rats IP injection (mL)

< 3

mice IV injection (mL)

< 0.15

rats IV injection (mL)

< 1

rabbits IM injection (mL)

< 0.5

safe blood collection volume for mice

< 0.3 mL

safe blood collection volume for rats

< 3 mL

safe blood collection volume for hamsters

< 1 mL

safe blood collection volume for rabbits

< 30 mL

what to do if larger volume of serum is requires to conduct the assay/test?

single animal - inadequate volume; terminal bleed - requires more animals, can’t follow progression over time; several animals, pooled sample, adequate volume, can follow animals over time

promoting vasodilation temperature

95-104 degrees F

promoting vasodilation in rat and mouse tail veins and rabbit ear veins

position thumb and forefinger on either side of tail or ear, apply gentle but firm pressure, use a stroking/milking motion over the vessel, starting at base and moving toward tip of tail or ear, repeat several times

subcutaneous injection cause of hypothermia

large volumes at room temperature may cause hypothermia

why the use of a vacutainer for blood collection in rodents may not be successful

collapses vessel, prevents collection of blood

location of the common vessels used for blood collection

tail, ear, face, eye, front legs, hind legs

lateral tail veins

mice and rats

marginal ear vein, central artery

rabbits

accessing marginal ear vein

pluck fur from ear or apply a warming pad or administer acepromazine or apply EMLA cream, use a 20-23 guage needle, apply pressure to the vessel near the base of the ear, insert needle bevel up, as material is injected the vessel will clear and then refill with blood

submandibular and facial veins

mice and rats

retro-orbital sinus (anesthesia required)

mice, rats, hamsters

cephalic vein

rabbits

accessing cephalic vein

crosses over the forearm, wet fur with alcohol or clip fur, apply pressure over vein near elbow, insert needle bevel up in a direction from the paw to the body, aspirate to confirm correct placement, use recommended IV injection volume

lateral and medial saphenous veins

mice, rats, hamsters, gerbils

accessing lateral saphenous vein

clip hair, swap with alcohol, put pressure above the insertion site to dilate the vessel, insert needle in the direction towards the body

metatarsal vein

gerbils, guinea pigs

methods for promoting vasodilation to facilitate blood collection

warm the whole animal or the area where blood will be collected - heating pad, heat lamp, warm water in glove, dipping tail in warm water

maximum IV injection volume (single bolus)

< 5 mL/kg

maximum IV continuous infusion volume

< 2-4 mL/kg/hour

subcutaneous injection port

requires anesthesia & surgery to implant, catheter in jugular or femoral vein, same constraints on infusion volume

chronic exteriorized IV catheter

requires anesthesia & surgery to implant, catheter in jugular or femoral vein, same constraints on infusion volume, self administration (drug abuse, psychiatric drugs, pain medication)

implantable osmotic pump

implanted subcutaneously, controlled release of drug over several days or weeks

intracerebral/intraventricular injection

direct one time injection into the brain, direct delivery to the brain avoids the blood-brain barrier

why indwelling catheter maintenance is required

to maintain sterility and prevent contamination; to prevent clot (thrombus) formation; to prevent the release of emboli

steps taken to prevent thrombus formation

after administration or blood collection, use a “heparin lock” solution to prevent clot formation

proper surgical scrub procedures practiced at the site of the skin incision

three alternating scrubs of betadyne solution and alcohol, start at center and spiral outward with scrub

laparotomy

clip site, surgical scrub, incise skin with scalpel (not scissors), use rat-tooth forceps to handle skin and abdominal muscles (less trauma, less crushing of tissues), elevate abominal muscles, cut along linea alba to open abdomen (elevation needed to avoid cutting abdominal organs)

thoracotomy

insert endotracheal tube, clip site, surgical scrub, incise skin with scalpel, use rat-tooth forceps to handle skin and intercostal muscles, cut intercostal muscles (between ribs), loss of negative pressure in chest cavity results in collapse of the lungs - need to manually inflate lungs or use a mechanical ventilator

appropriate use of surgical instruments for skin and muscles

use rat-tooth forceps to prevent excessive crushing of cells; use scalpel as cut causes less trauma to cells; scissors crush cells/tissue and delays healing; hemostats are used for blunt dissection of subcutaneous tissues and for clamping off bleeding vessels

swedged vs non-swedged needles

swedged needles have the suture contained within the end of the needle - does not stick out beyond cross-section of needle, less drag, less trauma to tissues; non-swedged needles have eyelet and suture must be looped though/round it and thus has a wider diameter than the needle itself allowing dragging/friction/trauma to the tissues delaying healing

when taper point needles should be used

for hollow organs, as cutting needles would allow for suture to tear through the tissue

when cutting point needles should be used

for skin, to facilitate passage of the needle though the denser tissue

why is perfect apposition of the wound margin appropriate

perfect apposition allows faster healing with minimal scar tissue formation; eversion or inversion of the wound margin results in scarring - scar tissue is not as strong as normal tissue

which tissues have greater or lesser tensile strength

skin > muscle fascia > muscle > subcutaneous fat

closing the body wall

the peritoneum and muscle fascia provide the strongest layers for retention of sutures, in rodents - 2 layer closure is sufficient - the peritoneum and muscle fascia are sutured as one layer - the skin is sutured as a seperate layer, dogs and larger species - a 3 layer closure is needed

ideal criteria for suture material

absolute sterility, uniformity of small size, high tensile (breaking) strength, complete and measured absorbability, economy, nonreactivity in vivo, pliability and handling qualities, nonslippage of knots, monofilament composition

general problems for suture material

tensile strength in vivo often not known; sutures are often selected for their mechanical properties, without consideration of the biological interaction of suture materials and tissues

simple interrupted

horizontal mattress

vertical mattress

simple continuous

continuous interlocking

simple interrupted advantages

good apposition of the margins, loss of one suture has minimal effect

simple interrupted disadvantages

takes a little longer to do than continuous suture patterns, may tear through tissue when tension present

horizontal mattress advantages

good for areas where tension tries to pull the margins apart, loss of one suture has minimal effect

horizontal mattress disadvantages

takes a little longer to do than continuous suture patterns, causes eversion of the margins, may “strangulate” blood flow and affect healing

vertical mattress advantages

good for areas where tension tries to pull the margins apart, loss of one suture has minimal effect, not as likely to restrict blood flow

vertical mattress disadvantages

takes a little longer to do than continuous suture patterns, cause eversion of the margins

simple continuous advantages

very fast to complete, fair apposition of the margins

simple continuous disadvantages

may tear through tissue when tension present or will break, breaking of suture allows entire wound to gape open

continuous interlocking advantages

very fast to complete, fair apposition of the margins, good for tension relief

continuous interlocking suture pattern disadvantages

breaking of suture allows entire wound to gape open

absorbable suture animal origin

derived from animal tissues - catgut (collagen, surgical gut, fascial strips); PGA (woven fibers, loses strength more rapidly than catgut); wicking - capillary action

nonabsorbable sutures

resist degradation by the body (metal, natural origin - silk, cotton, synthetic material - nylon, braided polyester polyethilene)

types of anesthetic methods

local, regional, general

general anesthesia

loss of consciousness and loss of sensation

analgesia

relief from pain

narcosis

seldom asleep, but is sedated and oblivious to pain

local anesthesia

loss of sensation (pain or otherwise) in a limited body area

regional anesthesia

loss of sensation over a larger area

factors affecting anesthesia

size, age, gender, recent feeding (increases BMR), fear and activity (increases BMR - sedate initially), tranquilizers (lowers BMR), concurrent disease (can increase or decrease BMR), hepatic microsomal enzyme activity, buildup of tolerance, interaction with other drugs

factors that affect metabolic rate

smaller animals have higher metabolic rates - need larger dose per body weight, neonates have low BMR, male BMR > female BMR

methods of anesthetic delivery

dermal/topical, injectable (IM, IV, IP, SC), inhalant

two body systems affected by “anesthetic emergencies”

cardiac, respiratory

four stages of anesthesia and the appropriate plane of anesthesia

stage 1 - rising pain threshold; stage 2 - excitement phase; stage 3 - surgical anesthesia - plane 3 (appropriate plane of anesthesia); stage 4 - respiratory paralysis

four methods for assessing adequate anesthesia/analgesia

jaw tone; swallowing reflex, withdrawal reflex (toe pinch), palpebral (eyelid), corneal reflex DISCRIBE

four criteria for selection of an ideal euthanasia method/agent

rapid death without signs of pain, panic, distress, minimum time to loss of consciousness; reliable, reproducible; number of animals to be euthanized, safety to personnel; minimum undesirable physiologic effects; minimal environmental impact; simple easy to use equipment

variables which are easily recognized and controlled

diet, environmental temperature, humidity, ventilation, light cycle, water, noise

variables which are difficult to recognize and control

animal genetics, latent disease, environmental contaminants, microbial transmission, subtle behavioral stressors, idiosyncratic reactions

physical factors that affect animal research

humidity, temperature, ventilation, noise, light

diseases caused by humidity

high humidity - heat stroke, reduces resistance to infection; low humidity - ringtail in rats and mice, increased dust accumulation, affects mucociliary escalator in lungs - with low humidity, the mucus layer dries up and the cilia stop moving

diseases caused by tempurature

heat stroke or chilling, can be affected by animal activity and number of animals in housing