Flashcards in Ramona's Notes - Chapter 18 Deck (54):
What do vet techs do with diagnostic samples?
What abilities must a vet tech possess to obtain diagnostic samples?
Ability to collect diagnostic samples
Should blood and urine samples be collected before or after administration of fluids or medications? And why?
Collect the supplies necessary for diagnostic sampling ahead of time, because the sample might otherwise be diluted or altered, if collected after given meds or fluids.
Samples should be collected with ...
Minimal trauma to vessels
Minimal stress to patient
Minimal discomfort to patient
Name some examples of laboratory tests affected by stress
- Release of stress hormones may alter samples
What's critical when performing venipuncture?
Proper restraint (animal must hold still and vein must be visualized)
Essentials for venipuncture
Needle and syringe
Vacutainer collection system
(double pointed needle, plastic holder, collection tubes - with and without anticoagulant)
Venipuncture method and needle gauge are dependent on ...
Amount of blood required
Intended use of the sample
(Use common sense, e.g. 22g needles are utilized in cats and small dogs, whereas 20g and 18g needles are used in large breed dogs and most farm animals)
Activated clotting time
Activated partial thromboplastin time
Which way should the bevel face on the needle?
The needle should penetrate the vessel on the first attempt!
What is the clotting cascade?
The manner by which the body repairs a cut or puncture in a vessel
When do you use 25 to 28g needles?
Multiple venipunctures (Glucose curve)
How much pressure do you apply to aspirate blood into a syringe?
Do not apply excessive negative pressure, pull back gently.
What can happen if excessive negative pressure is applied when aspirating blood into a syringe?
Hemolysis of RBC
False lab values
What do you do prior to venipuncture?
* Wipe hair and skin over the vessel with 70% isopropyl alcohol (this removes superficial skin contaminants, causes vasodilatation, improves visualization of vessel)
* It may be necessary to shave the hair over the vessel
* Blood draws for bacterial culture require aseptic technique
What is involved in proper restraint for venipuncture?
Avoid excessive restraint
Proper distention of blood vessel
Proper immobilization of blood vessel
Don't try blind attempts at venipuncture
Venipuncture in peripheral vein
Introduce needle into the occluded vessel (don't jab, place it!)
Place it as distally as possible
If necessary, reinsert the needle proximal to the previous site (move up a little bit)
Venipuncture in jugular vein
Introduce the needle in the caudal region of the jugular vein
Subsequent attempts can be made more cranially
Steps in venous blood collection
1. Attach a 20 to 25g needle to a 1 to 6mL syringe (size of vessel, how much blood do I need)
2. Occlude the vein with a tourniquet or digital pressure (fingers)
3. Wipe the skin and hair on top of the vein with an alcohol soaked cotton ball (70% isopropyl alcohol)
4. Insert the needle - bevel up - through the skin and into the vein at a 25 degree angle
5. Slowly retract the syringe plunger and collect a blood sample
6. Release the pressure on the vein and release the syringe plunger when a sufficient volume of blood has been collected
7. Remove the needle from the vein
8. Apply digital pressure to the venipuncture site as soon as the needle is removed until hemostasis occurs
What to do once blood collection is complete
1. Detach needle from syringe (blood forcefully ejected through the needle causes hemolysis)
2. Remove stopper from collection tube
3. Carefully transfer blood from syringe into the collection tube
4. If the tube contains an anticoagulant (EDTA): * replace stopper* gently invert the tube (purple top) to mix blood with anticoagulant - do not shake tube!!!
* You need enough blood to achieve the proper blood/anticoagulant ratio, otherwise you run the risk of obtaining false lab results
Which tubes should you invert?
Purple tops, they contain EDTA, an anticoagulant
(DO NOT invert red or tiger-top collection tubes! When collecting in these tubes you want the blood to clot)
Frequently used sites for canine venipuncture
Lateral saphenous vein (outside of leg)
Frequently used sites for feline venipuncture
Medial saphenous vein (inside of leg)
Arterial blood samples
* Usually done in ERs; not seen often
* Always done on horses under anesthesia to make sure they're ventilating well
Why are arterial blood samples done?
To assess pulmonary function - oxygenation and ventilation
How to collect an arterial blood sample
1. Percutaneous puncture of an artery (dorsal metatarsal, femoral or sublingual in an unconscious patient)
2. Coat a 1 to 3mL syringe with lithium or sodium heparin (expel excess heparin from syringe)
3. Collect supplies (vacutainer tube, cork, alcohol swab, thermometer)
4. When collecting the sample, do not introduce air and/or negative pressure
5. Upon completion, withdraw needle, apply digital pressure (hemostasis), expel air from syringe, cap syringe with cork and place in ice water bath if tests cannot be run immediately
Arterial catheter basics
- inserted for the continuous measurement of direct arterial BP
- inserted for collection of multiple arterial blood samples
- dorsal metatarsal artery
- over the needle catheter
- must be flushed with heparinized saline every 2 hrs
Urine sample collection basics
1. Common techniques:
Manual bladder expression
2. Collected and stored in:
Clean, dry containers (label jar or write on tape and tape it to jar, NOT lid, with PT name, time and date)
Refrigerated in secured, sealed containers
Collection procedures for routine UAs
1. Walk the dog and collect midstream sample
2. Collect from cage floor (PTs on elevated crates - use needle on syringe to suck it up)
3. Obtain free catch samples from clean & empty litter boxes (shredded wax paper, NOSORB - plastic litter or litter beads
4. Pour into a clean container (you only need a sterile cup, if you need a sterile sample)
Why is the free catch method not an acceptable means of collecting urine for culture?
As it could possibly contain bacteria, cells, debris from hair, skin and genitourinary tract
Manual bladder expression basics
1. May be difficult (usually done on anesthetized animals)
- trans-abdominal compression causes pressure inside the bladder to increase and urethral sphincter may not relax simultaneously
2. Place a hand on either side of the caudal abdomen
3. Isolate bladder between palmar surfaces of the fingers (should feel like a slinky)
4. Apply STEADY pressure until urine is produced
- don't keep pumping, exert gentle pressure
Indications for urinary catheterization
1. Urine sample collection
2. Empty the bladder
3. Relieve a urethral obstruction
4. Urinary tract access for radiographic studies
Conditions in which an indwelling catheter is indicated
1. Blocked tom
2. Measurements of urine output
3. Neurologic impairment (e.g. dog in wheelchair)
Complications resulting from catheterizations
* UTI (indwelling catheters)
* Urethral inflammation (bacterial infection)
* Trauma (increased RBC count, protein, transitional epithelial cells)
What unit are urethral catheters sized in?
F = French
Sizing urethral catheters
* Long length catheters should be premeasured externally on PTs
* Excessive lengths must not be advanced in smaller PTs
* Measurement is made to the caudal portion of the bladder
Polypropylene urinary catheters
* Rigid and easy to pass into the urinary bladder
* Used to collect samples or empty the bladder
* More comfortable
* Self retaining (has a balloon)
Placement of a catheter in a male dog
- Lateral recumbency (upper leg abducted)
- Clip long hairs around prepuce
- Flush prepuce with dilute antiseptic solution
- Rinse with warm sterile saline solution- Asst retracts prepuce to expose tip of penis
- Gently wash tip of penis with antiseptic solution and rinse with sterile saline
- Use STERILE GLOVES (treat like surgical prep)
- Remove catheter aseptically from sterile packaging
- Lubricate distal tip with sterile lube (catheter must be handled aseptically as it is advanced into the urethra)
- Never force a catheter (if it doesn't go, get a smaller French catheter as there might be stones in the way - urethral obstruction)
- You may encounter resistance at os penis (portion of urethra that curves around the curvature at the ischial arch; steady gentle pressure should overcome resistance)
- Urine should flow into catheter as it enters the neck of the bladder
- Advance either 1cm more or to the predetermined measurement
- Attach sterile syringe to catheter
- Slowly aspirate urine from bladder
- Discard first few mLs of urine (may contain contaminants)
- Remove catheter after completion of procedure
What to do if catheter in male dog is to remain in place
- Must be secured to prepuce (tape butterfly, stay suture loops)
- Should be foley catheter (inject an appropriate amount of sterile saline or water into the distal balloon cuff, there's a OW valve at the proximal end of catheter)
Catheterization in female dogs
Done very, very infrequently and is incredibly difficult.
Read pg. 608 in McCurnin and visualize description! Fair game for final!!!
Male cat catheterization basics
- Catheterizations of male cats are NEVER routine- Most commonly done to relieve urethral obstruction
- May or may not need sedation
- Obstructed cats are often obtunded (depressed) and/or hyperkalemic, evaluate and monitor this before administering anesthetic agent, hook up to ECG
Placement of a catheter in a male cat
- lateral or dorsal recumbency (hind legs drawn cranially)
- retract prepuce to expose penis- prepare perineum aseptically as with dogs
- observe tip of penis of obstructed cats (with glove palpate tip and look for distal urethral plug or calculus; gently massage tip to dislodge plug)
- with sterile gloves lubricate 3.5F polypropylene or silicone tomcat catheter- pass catheter into urethra
- if resistance is met, withdraw catheter slightly, rotate it and advance again
- if catheter still cannot be advanced, inject small amount of sterile saline and/or use sterile lube
- retropropulsion of urethral calculus (avoid excessive force and excessive volume of fluid as this may cause urethral trauma or rupture of urinary bladder)
- once catheter is placed and you have good urine flow, secure it in place, put an E-collar on cat and place it in cage grate
Catheterization of female cat
Much like dog
Read pg. 609 in McCurnin! Fair game for final!!!
What is a cystocentesis and why perform one?
1. It's percutaneous aspiration of urine from the bladder to obtain:
- a urine sample free of bacteria, cell and debris from lower urinary tract
- a sample of analysis (culture and sensitivity testing)
2. Minimizes iatrogenic urinary tract infections caused by catheterization
Why a cystocentesis?
Can aid in the localization of:
Last resort to empty an overly distended bladder (when urethral catheterization is impossible due to urethral obstruction)
Contraindications for cystocentesis
- Inadequate urine in the bladder
- PT resists restraint
- PT resists abdominal palpation
Complications of a cystocentesis
- Laceration of bladder
- Laceration of bowel (leading to peritonitis)
Never perform a cystocentesis on PTs with...
- Recent abdominal SX
- Abdominal trauma
- Suspected bleeding disorders (von Willebrandt's disease,...)
- Suspected caudal abdominal or bladder tumors
Supplies needed for a cystocentesis
22g 1 to 1.5 inch needle
12mL or larger syringe
How to insert needle into bladder
- Ventral (standing up) or ventrolateral (lying on side)
- depends on PTs positioning (standing, lateral or ventral recumbency)
- go at a 45* degree angle (so it can seal itself) DO NOT go straight!!!
- insert at a 45 degree angle cranial to trigone region of bladder
- if blood enters needle make another attempt, but use a fresh needle and syringe
- never redirect needle in abdominal cavity (laceration danger)
- always remember to release negative pressure on syringe before withdrawing needle
In male dogs:
- divert the prepuce and penis laterally
- insert needle on ventral midline or slightly paramedian
How much urine should be removed through cystocentesis?
Most but not all
- excessive pressure from full bladder could lead to extravasation of urine from puncture site
- removal of entire volume of urine increases risk of ctc between needle and bladder wall
pg. 606 Procedure 18-3 and Figure 18-22