SPECIMEN COLLECTION AND CONSIDERATIONS Flashcards
the act of obtaining a blood sample from a vein using a needle to a syringe or a stoppered evacuated tube; it is the most common way to collect blood specimens
Venipuncture
The major veins for venipuncture are in the:
antecubital fossa, the area of the arm in front of the elbow
Located near the center of the antecubital fossa; preferred vein because it is typically large, closer to the surface and the most stationary; most likely to bruise
Median cubital vein
Second-choice vein; often harder to palpate than median cubital vein; fairly well-anchored; often the only vein felt in obese patients
Cephalic vein
Last choice/least preferred; not well-anchored and rolls easily; increased risk of puncturing a median cutaneous nerve branch or the brachial artery; not recommended unless no other vein in either arm is more prominent
Basilic vein
Types of blood specimemns:
- serum
- plasma
- whole blood
Normally a clear, pale yellow fluid; separated from clotted blood by centrifugation (approx. 10 minutes at an RCF of 1,000 to 2,000g)
Serum
Normally a clear to slightly hazy, pale yellow fluid; separates from the cells when blood in an anticoagulant tube is centrifuged; contains fibrinogen
Plasma
Contains both cells and plasma; must be collected in an anticoagulant tube to keep it from clotting; used for most hematology tests and many point-of-care tests (POCTs), especially in acute care and stat situations
Whole blood
Methods of venipuncture:
- Evacuated tube system (ETS)
- Needle and syringe
- Butterfly set
preferred method because blood is collected directly from the vein into a tube, minimizing the risk of specimen contamination and exposure to the blood
Evacuated tube system (ETS)
Discouraged by CLSI due to safety and specimen quality issues; sometimes used on small, fragile, or damaged veins
Needle and syringe
Can be used with the ETS or a syringe; often used to draw blood from infants and children, hand veins, and in other difficult-draw situations
Butterfly set
Venipuncture equipment that restricts venous flow but not arterial flow:
Tourniquet
Tourniquet rule:
Must not be left on longer than 1 minute
Tourniquet dimensions:
1 inch wide x 15 inch long
considered standard needle gauge (adult) for routine venipuncture:
21 gauge
Three basic components of ETS:
- Multisample needle
- Tube holder
- Evacuated tubes
usual needle gauge for butterfly system
23 gauge - most commonly used for phlebotomy; used among children
A handheld medical device that helps medical staff visualize veins before phlebotomy. The device emits infrared light and is held about 7 inches over the potential phlebotomy site
AccuVein
Order of Draw:
- Sterile tube (blood culture)
- Coagulation tube (blue top)
- Serum tube with or without clot activator, with or without gel (Red top)
- Heparin tube with or without get separator (green top)
- EDTA tube with or without get separator (lavender top, pearl top)
- Glycolytic inhibitor tube (gray top)
Mnemonic:
Stop - Sterile
Light - Light blue
Red - Red
Stay - SST (serum separator tube)
Put - PST (plasma separator tube)
Green - Green
Light - Lavender
Go! - Gray
Lengths of lancet should be:
less than 2.0 mm to avoid penetrating the bone
Sites for capillary puncture:
- Palmar surface of 3rd and 4th fingers
- Lateral plantar heel surface (newborns)
- Earlobes
Capillary order of draw (CLSI)
- EDTA specimens
- Other additive specimens
- Serum specimens
What equipment is used for drawing blood for blood gas analysis:
Syringe
syringe are used instead of evacuated tubes because of the pressure in an arterial blood vessel
Preferred anticoagulant for blood gas analysis:
Heparin/ 0.05 heparin/mL of blood
Primary arterial sites:
Radial artery
Brachial artery
Femoral artery
It is done before collecting arterial blood from radial artery; to determine whether the ulnar artery can provide collateral circulation to the hand after the radial artery puncture.
Modified Allen test
Diurnal variations
Increase in AM:
Increase in PM:
Diurnal variations
Increase in AM: ACTH, Cortisol, Fe, Aldosterone
Increase in PM: ACP, Growth hormone, PTH, TSH
Recent food ingestion
increase:
decrease:
Recent food ingestion
increase: Glucose, insulin, triglycerides, gastrin, ionized calcium
decrease: Chloride, phosphorus, potassium, amylase, ALP
Stress
increase:
increase: ACTH, cortisol, catecholamines, prolactin
First hormone to increase during stress:
Catecholamines
Parameters that require fasting:
FBS
GTT
Triglycerides
Lipid panel
Gastrin
Insulin
Aldosterone/Renin
Parameters that increases in Hemolysis:
Potassium
PO4
Fe
Magnesium
ALT
AST
LD
ALP
Catecholamines
CK (marked hemolysis)
Anaerobic and require ICE slurry (immediate cooling)
Lactic acid
Ammonia
Blood gas (if not cooled = decrease pH and pO2)
“LAB”
Routine specimens ideally delivered to the laboratory wihthin:
45 minutes of collection
Routine specimens are centrifuged within:
1 hour of arrival if serum or plasma is needed
Maximum time limit for serum or plasma separation is:
2 hours after collection (CLSI standard)
a medical term meaning “immediately”; collected and analyzed immediately; given the highest priority and are usually ordered from the emergency department and critical care
Stat collections
Analytical patient-testing activities provided within the institution, but performed outside the physical facilities of the clinical laboratories; Laboratory testing that is performed outside the central or core laboratory and generally at the site of clinical care or close to the patient
Point-of-Care testing (POCT)
The highest-volume POC test in most health care institutions
POC glucose
Most common POCT specimen:
Capillary blood
