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MLAB 123 > 5 - Skin puncture > Flashcards

5 - Skin puncture Flashcards

1
Q

Skin puncture (dermal puncture) or capillary puncture is

A

procedure in which the skin is punctured with a lancet to obtain a capillary blood sample for laboratory testing.

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2
Q

Reason for Capillary Puncture

A

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
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3
Q

A skin puncture is NOT appropriate when:

A

-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

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4
Q

Composition of Skin Puncture Blood

A
  • 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.
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5
Q

Precautions

A 
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
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6
Q

Patient Preparation and Identification

A 
Check patient requisition
 	Greet and identify patient
 	Explain the procedure
 	Verify any diet restrictions
 	Wash hands and put gloves on
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7
Q

Site selection

A

-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

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8
Q

Heel Puncture Sites

A

-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

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9
Q

Finger Puncture Sites

A

-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

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10
Q

Pink lancet

A

MEDIUM FLOW –

21- Gauge x 1.8 mm depth

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11
Q

Blue lancet

A

High Blood Flow

1.5 mm width x 2.0 mm depth

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12
Q

Purple lancet

A

LOW FLOW –

30-Gauge x 1.5 mm depth

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13
Q

Tips for a good blood flow

A

-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

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14
Q

The Lasette

A

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
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15
Q

Order of Draw for Skin Puncture

A

-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

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16
Q

Consequences of not mixing capillary blood samples after dermal puncture.

A

Tubes with anticoagulants will clot.
BD SST™ Tubes may not clot completely.
Specimen may need to be recollected.

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17
Q

What to use Evacuated tubes for

A

Routine and STAT collections

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18
Q

What to use Butterfly needle for

A 
Small veins 
Fragile veins
Blood Culture bottle
Small children
Difficult draw
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19
Q

What to use Dermal Puncture for

A 
Children ; infants
The Elderly patient
Oncology patients
Burned patients
Obese patients
Tiny veins
Home testing
Procedure requiring Capillary samples only
POCT
20
Q

PKU and Hypothyroidism

A
  • 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.
21
Q

Congenital hypothyroidism

A

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
22
Q

Neonatal Bilirubin

A

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

23
Q

Point of Care Testing (POCT)

A
  • 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.
24
Q

Yellow top tube

A
  1. Microbiology- SPS (sodium polyanethol sulfonate )-neutralize antibiotics
  2. ACD (acid citrate dextrose-maintain cell viability)- Used for blood bank, HLA typing
25
Q

Trace Metals Tests

A

1Royal Blue top tube

  • May contain a clot activator or EDTA
  • Contain low levels of trace metals (Aluminum, lead , mercury , zinc and other metals )
  • Used for trace metal , nutritional and toxicology blood collection
26
Q

Tan Top tube

A

Contain EDTA

  • Contain low level of lead
  • Used for blood lead level
27
Q

White top tube

A

Contain EDTA + plasma separator

DNA and molecular diagnosis test

28
Q

Orange Top Tube

A

Contain thrombin

Used for STAT tests

29
Q

Fasting Specimens (FBS)

A
  • The patients eat or drink nothing other than water for a 8 to 12 hours prior to having their blood drawn.
  • Common test are cholesterol, triglycerides and glucose determinations.
  • phlebotomist’s responsibility
30
Q

Oral Glucose Tolerance Test (OGTT)

A

• Used to diagnose carbohydrate metabolism disorders such as diabetes mellitus (lack of insulin) and hypoglycemia(low blood sugar).
• The Canadian Diabetes Association’s clinical
practice guidelines for diabetes mellitus——-
fasting plasma glucose test >7.0 mmol/L and A1C > 6.5%
• CDA new recommendation: that anyone with a risk factor for diabetes and a fasting plasma glucose level between 6.1 and 6.4 mmol/L and Hgb A1C 6.0-6.4 % should be considered for an oral 2 hr glucose tolerance test
• OGTT can be in conjunction with hemoglobin A1C level

31
Q

Therapeutic Drug Monitoring.

A
  • Measures the amount of a particular medication in the patient’s bloodstream (dependent on age, age, metabolic rate, kidney function etc)
  • Used to determine the optimal dose of a medication for a patient.
  • Two blood samples are needed (trough and peak levels.)
  • The trough level is the least amount of the medication found in the blood just prior to administration of the net dose of medication.
  • The peak level occurs when the largest amount of the medication is found in the bloodstream. The drawing time of the peak level varies with the type of medication.
  • cortisol and iron is affected by the time of day
  • Tested for trace metals such as arsenic or lead.
  • The blood must be collected in a royal blue stoppered metal free tube. (no anticoagulant)
32
Q

Alcohol Levels

A
  • When drawing for alcohol testing, use a disinfectant solution other that alcohol.
  • Solutions such as zephrin chloride, soap or hydrogen peroxide are acceptable.
  • Do not use Betadine, iodine swabs or chlorohexadine because these contain alcohol.
  • Care must also be taken with these specimens because the results are often needed for legal reasons
33
Q

Neonate Bilirubin Test

A

Breakdown bi-product of RBC
Blood sensitive to light
Collect in amber microtainer
Deliver to the lab ASAP

34
Q

Chain of Custody

A
  • Accounts for the specimen from the time of collection to the final deposition…guarantees the specimen integrity in a court of law
  • Test result for alcohol, toxicology and forensic science tests may be used in a court case
  • Legal specimens require special handling
  • Specimen must be correctly identified…making sure the specimen has not been altered , replaced or tampered with
35
Q

Procedure

A
  1. Specimen Collection-correct patient ID
  2. Chain of custody form must be completed correctly
  3. Phlebotomist and others handling the specimen must date and sign
  4. Specimen kept in a locked container
  5. Several copies of the chain of custody form
  6. Patient may be required to sign or initial the form
36
Q

Edematous

A

buildup of fluids ..specimen will have abnormal amount of interstital fluid
if both hand edametous - venipuncture

37
Q

Good flow

A

increases blood flow 7 fold
let alcohol dry - can cause hemolysis
no spring loaded device for glucose monitoring
wipe away first drop - interstitial fluid

38
Q

iatrogenic anemia

A

repeated blood collections if exceeds 10% of total blood volume or exsaniguination

39
Q

additive reflux

A

when blood mixed with additive is put back into patients vein

40
Q

tendon

A

tight and stringy

41
Q

venous reflus

A

backflow of blood into veins

42
Q

neonatal screening tests

A

biotinidase, cystic fibrosis, galactosemia, hypothyroidism, PKU , sickle cell

43
Q

Biotinidase

A

biotinidase deficiency

biotin needs for fatty acid synthesis, amino acid breakdown

44
Q

CF

A

when mucus accumulates in people

collect blood on Guthrie card and then sweat test - measuring amount of salt in sweat

45
Q

galactosemia

A

body cannot use galactose as an energy source

wont gain weight

46
Q

hypothyroidism

A

low thyroid

need thyroxine

47
Q

PKU - Phenylketonuria

A

build up of phenylketone in the blood because the body does not have the enzyme to break it down
if untreated can damage brain tissue
in addition to first screening the child should be tested in 10-15 days

MLAB 123 (11 decks)

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