Collection of Blood and Other Samples From Lab Animals

reasons for collecting blood

→ assessment of individual animal health status

• hematology

• clinical chemistry

→ sentinel animal testing for assessing colony disease status

→ analysis of biochemical, metabolic, toxicological or immunological parameters

→ pharmacokinetic studies

→ examination or culture of microorganisms

→ collection of antibodies (monoclonal or polyclonal antibody production)

reason for selection of a particular blood collection technique/site

→ the purpose of the blood collection

→ the need for an arterial vs venous sample

→ the duration and frequency of sampling

→ the impact on animal welfare

→ the health status of the animal being bled

→ whether the sample is taken during a terminal procedure

→ the potential for stress-induced effects on biochemical and hematological parameters

→ the training and experience of the staff involved

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

→ single animal, inadequate volume

→ terminal bleed, adequate volume; requires more animals; can’t follow progression over time

→ several animals, pooled sample, adequate volume; can follow animals over time

promoting vasodilation

→ increasing the diameter of the vessel and the flow/volume of blood makes blood collection easier

→ warm the whole animal or warm the area where blood collected

→ heat lamp, electric heating pad

promoting vasodilation in rat & mice tail veins / 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

blood collection sites

→ lateral & medial saphenous veins → rats & mice

→ submandibular venipuncture → rats & mice

→ retro-orbital sinus plexus → rats & mice (anesthesia strongly recommended)

cardiac puncture

→ animal must be anesthetized

→ place in dorsal recumbency

→ palpate the xiphoid process, a cartilage flap at the base of the sternum

→ the needle will be inserted in the “left cardiac notch” between the xiphoid and the ribs

→ the needle should be directed cranially

→ after penetrating the skin, begin to pull back on the plunger

→ when blood can be seen in the needle hub, stop advancing the needle, and draw the blood sample

→ if the blood stops flowing:

• slowly rotate the barrel of the syringe in case the bevel is up against the heart wall

• if that doesn’t work, slowly move the needle inwards by millimeters, or back out by millimeters, continuing to apply a vacuum by aspirating with the plunger

issues with cardiac punctures

→ ideally, a terminal procedure

→ if done multiple times, will cause scarring of the heart muscle, affecting nerve signaling for contractions, resulting in arrhythmias

→ if blood escapes into the pericardial sac, will result in pericardial tamponade

→ blood escaping from the puncture site into the thorax will result in hypovolemia, shock, and death

blood collection sites in hamsters

• retro-orbital

• lateral saphenous

• cephalic vein

• cranial vena cava

gerbil blood collection sites

• retro-orbital sinus

• lateral saphenous

• metatarsal vein

catheter maintenance

• need to maintain “patency” of catheter (for infusion or withdrawl)

• need to prevent contamination & septicemia

• a thrombus (clot) can form around the outside and within the lumen

• thrombus prevents withdrawal of blood or injection of fluid or drugs

• a thrombus can serve as a site for bacterial colonization

• “blowing out” the thrombus with pressure results in an embolus, which can lodge in and block smaller vessels and capillaries with a potential life threatening effects

heparin lock

→following blood withdrawal of infusion, flush catheter with sterile physiological saline

→ flush & heparin lock at least once every 1-2 days

→ inject 10-100 units/ml of a heparin/saline solution - just enough to fill the catheter

→ insert the sterile plug (obturator) to close the catheter

→ avoid over-heparinization of the animal

antithrombogenic catheter materials

• a heparin-bonded coating minimizes fibrin adherence & thrombus formation

• also bonding the catheters with benzalkonium chloride provides antimicrobial activity

• renothane is a brand of catheter which is highly antithrombogenic

urinalysis

→ qualitative

• veterinary / clinical: assessment of animal health

→ quantitative:

• research / testing: assessment of result of experimental manipulation

  • assessing renal (kidney) function

  • study of renal disease or renal toxicity

  • evaluating endocrine or metabolic abnormalities

  • evaluating excretion of drugs, test agents, and their metabolites

free-catch urine sample

• mice and rats with usually urinate a small quantity of urine when they are picked up out of their cage

• this can be collected with a microhematocrit tube of in an eppendorf tube

• they can also be picked up or placed on a surface covered with plastic wrap

external bladder massage/compression urine collection

digital pressure can be applied to the abdomen in the area of the bladder, and the compression may lead to voiding of urine

cystocentesis urine collection

the bladder is palpated and stabilized, then a sterile hypodermic needle is passed through the skin into the bladder, and urine is drawn up into the syringe

urethral catheterization

• the urethra in mice and rate is located in the genital papilla

• anesthesia required

• 22 or 26 gauge angiocath catheter

• ensure that not over-inserted, resulting in puncture of the wall of the bladder, with leakage of urine into the abdomen

metabolic cage urine sample collection

• single animal placed in unit for 24 hrs or more

• food and water source external to unit, avoids contamination of samples

• based on the shape of the apparatus, feces fall down into one container, and urine into another container

• urine samples should be retrieved every 4 hrs or collection vessel cooled to prevent degradation/breakdown of urine constituents

biopsy

collection of tissue sample from a living animal

necropsy

collection of tissue samples from an animal that has been euthanized

collection of tissue samples

→ Testing offspring to determine if they possess desired transgenes

→ PCR testing of tail snips or ear punches

→ Anesthesia required over 14 days of age

→ least painful method should be selected