Capillary blood
Acquired by skin puncture is different from that if venous or arterial blood samples acquired by other methods
Lab tests commonly performed using Capillary Blood Soecimens
- blood smears fir white cell differential (manual blood spears on microscope)
- CBC, H&H
- Electrolytes
- Neonatal bilirubin
- Neonatal blood gas
- Neonatal screening (using filter paper or blood spot testing)
- Point of care testing (POT) and/ or home testing (blood glucose monitoring) etc
Capillary is more of a mixture composed of blood from
- arterioles
- venules
- capillaries
- intracellular and interstitial(tissue) fluids(fluids that form from within tissue layers and gaps
Warming the skin puncture site
- Helps increase arterial blood flow to the area arterializing the site
- Can be warmed with a heated surgical towel or a washcloth heated with warm water to 42 degrees celcius won’t burn skin
Cleansing skin puncture site
- Should be gleaned with a 70% aqueous solution of isopropyl alcohol before being punctured
- If alcohol drips or pools at site it can cause hemolysis and contaminate testing for glucose determination
Average depth of a skin puncture should be
- 2 to 2.5mm for adults
- less than 2.0mm for small children and infants avoids hitting the bone
- Laser devices are also available as alternative (250 um wide and 1-2mm deep)
Cyanotic
Cold (blue in color due to O2 depletion or swollen
Warming hand to increase blood flow
Wrap it in a warm towel for 3 to 5 minutes or use warning device/ heating pack
Order of collection
- Blood gases
- EDTA specimen for hematology tests
- Other tubes with additives
- Serum tubes
Microcollection tubes
- Must be adequately filled and if contain additives should be mixed gently
- If takes to long to fill tube microclots may form
- hemolysis of capillary blood specimen is a complication
- excessive amounts cause clot formation
- inadequate amounts cause cells to change morphologically cause to much anticoagulant
Controlling the depth of the skin puncture prevents
Osteomyelitis
The fleshy central palmar surface if the distal phalanx ( fingertip section)
Of the third or fourth finger of the nondominant hand is the preferred site for puncture
For infants less than 1 year old or neonates the recommended site for skin puncture is
Lateral or medial plantar surface of the heel
Skin puncture is most useful in which if the following conditions
Fragile veins
Plastic Microcollection tubes should be filled with blood in which of the following ways
Using capillary action to fill itself
Controlling the depth of the skin puncture prevents
Osteomyelitis
What does feathered edge refer to
Edge of the blood smear on a microscope tube
Blood films for microscopic slides
From fresh drops of blood perform finger puncture in the usual way wipe first drop of blood away
Touch the slide to the second drop at 0.5-1 inch ;1.3-2.5cm from the end of the slide
Not recommended for routine skin punctures
- Earlobe
- central arch area of infants heel
- fingers of a newborn or infant less than 1 year old
- the pinky ( risk of hitting bone)
- the thumb ( has a pulse)
- the index finger (more sensitive likely to be callused)
- fingers on side of a mastectomy (removal of lymph nodes during surgery may result in excessive lymph fluid on the side of the surgery
- swollen,infected,callused,burned,cut,scared,bruised,rash,previously punctured sites (because accumulated fluid may contaminate the specimen and site may be bruised causing more pain if punctured again)
