ch 10: capillary puncture equipment, principles, and procedures

what tool is used to puncture/make an incision in the skin?

lancet

what does lancet length and depth selection depend on?

patient age, collection site, volume of specimen (blood) required, puncture or incision depth needed to collect an adequate specimen without injuring bone

microcollection

collecting small amounts of blood by capillary puncture

microtubes/”bullets”

special small plastic tubes used to collect the tiny amts of blood obtained by capillary puncture

microhematocrit tubes

disposable, narrow-bone plastic/plastic-clad glass capillary tubes that fill by capillary action

which color tubes are used for Hct testing? what additive do they have?

lavender, EDTA

is it important to warm the site before performing heel punctures on newborns?

yes

what part of the capillaries do we puncture?

the capillary bed

what kinds of fluids are capillary specimens composed of?

arterial, venous, and capillary blood, interstitial fluid, intracellular fluid

examples of capillary puncture being an appropriate choice for older children and adults

• available veins are fragile, difficult to access, or must be saved for other procedures such as chemotherapy

• several unsuccessful venipunctures have been performed, and the requested test can be collected by capillary puncture

• the patient has burns or scars at sites commonly used for venipuncture

• the patient has thrombotic or clot-forming tendencies

• the patient is apprehensive or has an intense fear of needles, and capillary collection is acceptable

• the patient is extremely overweight, and veins are difficult to find

• there are no accessible veins (e.g., the patient has IV lines in both arms, or the only acceptable sites are in scarred or burned areas)

• blood is being obtained for point-of-care testing (POCT) procedures such as glucose monitoring

which four kinds of tests cannot be collected by capillary puncture?

most erythrocyte sedimentation rate methods (ESR is hematology test), coagulation studies that require plasma specimens, blood cultures, and tests that require large volumes of serum or plasma

CLSI-recommended order of draw for capillary specimens

• blood gas specimens

• EDTA specimens (lavender-top hematology tubes)

• other additive specimens

• serum specimens

where are capillary specimens collected from adults and children over 1 year old? what about from infants less than a year old and occasionally toddlers?

finger (fingerstick), heel (heelstick)

how should someone be positioned for finger puncture? what about for heel puncture?

lying down or seated in a reclining chair with arm slanted downward, hand extended, palm up. supine (lying face up) with the foot lower than the torso

if the patient doesn’t have a preference of which hand to use, which hand should you use?

nondominant hand

cyanotic

bluish in color. do NOT select this as a puncture site

CLSI-recommended site for capillary puncture on adults and children older than 1 year

palmar surface of the distal segment (end segment) of the middle or ring finger of the nondominant hand. should be in the central, fleshy portion of the finger, slightly to the side of center and perpendicular to the grooves in the whorls (spiral pattern) of the fingerprint

which finger should you ALWAYS avoid?

pinky

depth of penetration of lancets for finger punctures on infants btwn 6 months to 1 year of age, given that the infant weighs more than 10 kg

penetrate 1 mm or less

what two conditions can puncture of the bone cause?

osteomyelitis, osteochondritis

osteomyelitis

inflammation of the bone marrow and adjacent bone

osteochondritis

inflammation of the bone and cartilage

how deep should punctures be for heel punctures? why?

2 mm or less. heel bone (calcaneus) is 2.4 mm below the skin

safest areas for heel puncture

medial and lateral portions (so avoid the center) of the plantar surface (sole or bottom) of the heel. image on pg 362

a specimen obtained from a warmed site is described as being

arterialized

5 heel puncture precautions

• do not puncture deeper than 2.0 mm

• do not puncture areas between the imaginary boundaries

• do not puncture in the arch or any other area of the foot other than the heel

• do not puncture the posterior curvature of the heel

• do not puncture through previous puncture sites

how is warming a site accomplished?

wrap the site for 3-5 minutes with a washcloth, towel, or diaper that has been moistened w comfortably warm water or using a commercial heel-warming device

what should you NOT use to clean skin puncture sites?

povidone-iodine

with very young children, how many fingers should you grasp btwn ur fingers and thumb?

3-4 bc the child cannot twist away as easily

should you squeeze/apply more pressure if no blood is coming out?

no. just lower the finger/heel and hold gentle pressure until a large drop of blood forms at the site

do you wipe away the first blood drop?

yes, with a clean gauze pad

when do you label specimens?

immediately after specimen collection in front of the patient, parent, or guardian

should you apply bandages to infants and children under 2 years of age?

no

kernicterus

brain dysfunction caused by toxic levels of bilirubin

what must be turned off when collecting a bilirubin specimen?

phototherapy light

how are bilirubin specimens usually collected? in what tubes?

heel puncture, amber-colored microcollection containers

newborn screening (NBS)

state-mandated testing of newborns to identify rare but srs health conditions that can be present at birth even though affected infants may not show symptoms of them at first

when are NBS tests ideally performed?

when an infant is btwn 24 to 72 hrs old

4 required NBS tests

phenylketonuria (PKU), hypothyroidism, galactosemia, cystic fibrosis (CF)

phenylketonuria (PKU)

genetic disorder characterized by a defect in the enzyme that breaks down the amino acid phenylalanine, converting it into the amino acid tyrosine. leads to increased phenylketones in urine

hypothyroidism

a disorder characterized by insufficient lvls of thyroid hormones

galactosemia

inherited disorder characterized by lack of the enzyme needed to convert the milk sugar galactose into glucose needed by the body for energy

cystic fibrosis (CF)

genetic disorder caused by one or more mutations in the gene that directs a protein responsible for regulating the transport of chloride across cell membranes. primarily affects the lungs and pancreas

how are NBS tests usually done?

blood spot collection obtained by heel puncture

blood film/slide/smear

a drop of blood spread thin on a microscope slide

what is a Diff test? what is required to perform a manual differential (Diff) test?

a test in which the number, type, and characteristics of blood cells are determined by examining a stained blood smear under a microscope

blood film/slide/smear

which department+color tube w what additive makes blood smears? consequently, what department+color tube do Diff tests such as CBC belong to?

hematology, lavender-top, EDTA

when preparing a smear manually from an EDTA specimen, how long should the tube of blood first be mixed for?

2 minutes minimum

thick blood smears are most often requested to detect the presence of

malaria