5 - Skin puncture Flashcards
Skin puncture (dermal puncture) or capillary puncture is
procedure in which the skin is punctured with a lancet to obtain a capillary blood sample for laboratory testing.
Reason for Capillary Puncture
The procedure is performed on pediatric under the age of 2 years and adult patients who are difficult to get blood
- Children under 2 years old have small veins which collapse
- Infant and children have small blood volume- collecting lots of blood can lead to anemia
- Infants with small vein (premature babies)
- Tests are ordered that require only a small amount of blood
- Unsuccessful repeated venipunctures
- The patient has severe burns, scars is obese or elderly
- The patient has thrombotic tendencies
- The patient’s veins must be reserved for therapeutic purposes (chemotherapy)
- The patient has fragile superficial veins (the elderly)
- Patients requiring home glucose monitoring and point of care tests
A skin puncture is NOT appropriate when:
-The patient is severely dehydrated (falsely increased hemoglobin)
-The patient is in shock
-The patient has chronic poor circulation
-The patient is extremely cold. (falsely increased hemoglobin)
-More blood than can be obtained by a skin puncture in needed for testing.
-The area has scars, bruises or rashes
-The area is edematous (sample diluted by interstitial fluid)
-ESR and blood culture is ordered
do not do on side with masectomy - increased risk of infection
Composition of Skin Puncture Blood
- A combination of blood from -capillary, arterial , venous blood and interstitial fluid))
- Because of arterial pressure, the blood resembles arterial blood than venous blood.
- Interstitial fluid (fluid present between tissues) is released due to tissue damage.
Precautions
Do not use the first drop of blood -Excessive squeezing causes hemolysis lavendar tube needs 250-500 micro L and green needs 400-600 micro L overfilling causes hemolysis
Patient Preparation and Identification
Check patient requisition Greet and identify patient Explain the procedure Verify any diet restrictions Wash hands and put gloves on
Site selection
-Select sites that provide sufficient distance between the skin and the bone.
-Contact with the calcaneus bone can cause infection (osteomyelitis).
-The primary dermal puncture sites are the heel and the distal segments of the third and fourth fingers.
-The plantar surface of the large toe is also acceptable.
- Dermal punctures on earlobes is usually not recommended
-Never puncture a previous puncture-causes infection
-If the site is cold warm a damp towel and placed on the site for at least 3 minutes
- thumb (1st) or pointer (2nd) are not good because the skin is too thick and calloused
not picky because the bone is too close to the skin
always go across the fingerprint lines ( \ / ) on finger
Heel Puncture Sites
-Used on infants less than 1 year of age
-The heel contains more tissue than the fingers
-Puncture the medial and lateral areas of the plantar (bottom) surface of the heel.
-In small or premature infants, the heel bone (calcaneus) may be no more than 2.0mm beneath the plantar heel-skin surface
-The distance between the skin and the calcaneous (heel bone) is greatest.
-No more than 2.0 mm on premature babies or small infants
-In larger infants, the plantar surface of the large toe may be used
-Hold the heel firmly in the nondominant hand with the thumb below the heel and the index finger over the arch.
-Hold firmly but not too tightly to ensure continuous flow of blood.
-The dominant hand places the lancet (incision 2mm) firmly against the skin perpendicular to the heel.
never do it on a walking child
Finger Puncture Sites
-Performed on adults and children over 1 year of age.
-Areas of choice- fleshy areas located near the center of the third and fourth fingers on the palmer side
-Make the incision perpendicular to the fingerprint swirls.
- A perpendicular puncture will cause the blood to form a droplet.
-A parallel puncture will cause the blood to flow down the finger instead of forming a nice round drop.
- The automatic lancet is placed in firm contact with the skin before the incision is made
non dominant hand
Pink lancet
MEDIUM FLOW –
21- Gauge x 1.8 mm depth
Blue lancet
High Blood Flow
1.5 mm width x 2.0 mm depth
Purple lancet
LOW FLOW –
30-Gauge x 1.5 mm depth
Tips for a good blood flow
-Warm the puncture site to increase blood
flow
-Hold the puncture site downward and gently apply intermittent pressure to the surrounding tissue.
-Strong repetitive pressure (milking) must be avoided; it may cause hemolysis or tissue-fluid contamination of the specimen.*
dont scrap- hemolyze or blot blood
keep below heart level
gently tap after each drop
The Lasette
battery operated
- In July 1998, the FDA cleared it for home use in glucose and hematocrit blood collection
- For ages 5 years old to adult.
- Needle-less blood sampling.
- The adjustable depth laser evaporates a small sample of tissue, allowing quality samples to be taken with no incision or needles to be disposed of.
- Expensive-About $1000 US
Order of Draw for Skin Puncture
-Blood gas or pH specimen (capillary tube)
-Slide for blood cell differential ( prevent platelet clumps)-depends on institution
-Hematology specimens-mix by inversion 8x - Lavendar
- Chemistry or other specimens-invert 10x
-Green top
-Gray top
-Yellow top
-Red top- chem and BB
NB: Blood cultures cannot be collected by skin puncture
Consequences of not mixing capillary blood samples after dermal puncture.
Tubes with anticoagulants will clot.
BD SST™ Tubes may not clot completely.
Specimen may need to be recollected.
What to use Evacuated tubes for
Routine and STAT collections
What to use Butterfly needle for
Small veins Fragile veins Blood Culture bottle Small children Difficult draw
What to use Dermal Puncture for
Children ; infants The Elderly patient Oncology patients Burned patients Obese patients Tiny veins Home testing Procedure requiring Capillary samples only POCT
PKU and Hypothyroidism
- Testing done on all newborns
- Screening test for phenylketonurea (PKU)
- The filter paper should be touched gently against the large blood drop
- Allow a sufficient quantity of blood to soak through to completely fill the preprinted circle on the filter paper.
- Do not press the paper against the puncture site of the heel.
- Blood should only be applied to one side of the filter paper.
- Examine both sides of the filter paper to assure that the blood uniformly penetrated the saturated paper.
- The filter paper discs are place on bacteria culture media and growth or no- growth is observed
- PKU is a hereditary metabolic disease caused by lack of the enzyme phenylalanine hydroxylase and can result in severe mental retardation if not detected soon after birth.
- Early detection…diet that is low in phenylketones…less chance of mental retardation.
Congenital hypothyroidism
condition in which the thyroid gland is impaired due to production of defective enzymes.
- Newborns should be tested of these diseases between the ages of 24 and 72 hours.
- If left untreated can lead to mental retardation
- Hypothyroidism is detected by performing immunochemical analysis of the dried blood
Neonatal Bilirubin
Cause of increased serum bilirubin in newborns:
Hemolytic disease of the newborn (HDN)
The liver is not developed enough to process the bilirubin produced from the normal breakdown of red blood cells.
Increased bilirubin can accumulate in the brain and cause permanent or lethal damage.
Specimens must be protected from excess light during and after the collection. (Amber colored Microtainer tubes used)
Infants appear jaundiced and are placed under ultra-violet light
Point of Care Testing (POCT)
- Clinical testing is done at the patient’s side (point of patient care) rather than in the clinical laboratory.
- Not a replace for clinical testing but a supplement
- Testing done in the emergency rooms, critical care units, clinics and nursing homes
- Most frequent test is Glucose
- Other tests blood gas analysis, coagulation tests and common chemistry tests such as for electrolytes and cardiac enzymes.
Yellow top tube
- Microbiology- SPS (sodium polyanethol sulfonate )-neutralize antibiotics
- ACD (acid citrate dextrose-maintain cell viability)- Used for blood bank, HLA typing
