PMLS 2 - Capillary Puncture Equipment and Procedures

Lancet

sterile, disposable, sharp-pointed or bladed instrument that either punctures or makes an incision in the skin to obtain capillary blood specimens for testing

finger puncture or heel puncture

Lancets are specifically designed for either _______________ and must have OSHA required safety features

important OSHA required lancet safety feature

permanently retractable blade or needle point to reduce the risk of accidental sharps injury

Laser lancets

perforate the skin with a laser instead of a sharp instrument

Laser lancets

typically vaporizes water in the skin to produce a small hole in the capillary bed without cauterizing delicate capillaries

Laser lancets

no risk of accidental sharps injury, and no need for sharps disposal

Lasette® (Fig 10-1C) (Beijing Sincoheren Science & Technology Developing Co., Ltd, Beijing, China)

has single-use, disposable inserts to prevent crosscontamination between patients

Lasette® (Fig 10-1C) (Beijing Sincoheren Science & Technology Developing Co., Ltd, Beijing, China)

It is cleared by the FDA for use on the fingers of adults and children 5 years of age and older

Use on children younger than 5 years of age

subject to a physician’s discretion

Microcollection containers

also called microtubes,

Microcollection containers

special small plastic tubes used to collect the tiny amounts of blood obtained from capillary punctures

Microcollection containers

They are often referred to as “bullets” because of their size and shape

Microcollection containers

narrow plastic capillary tubes to facilitate specimen collection

color-coded bodies or stoppers

correspond to color-coding of ETS blood collection tubes, and markings for minimum and maximum fill levels that are typically measured in microliters (L) ,such as 250 L and 500 L, respectively

BD Microtainer® MAP

has a penetrable septum for use with automated hematology systems

Microhematocrit tubes

disposable, narrow-bore plastic or plastic-clad glass capillary tubes that fill by capillary action and typically hold 50 to 75 L of blood

packed cell volume (PCV)

used primarily for manual hematocrit (Hct)

tubes come coated with ammonium heparin

collecting Hct tubes directly from a capillary puncture, or plain, to be used when an Hct tube is filled with blood from a lavender-top tube

Heparin tubes

typically have a red or green band

nonadditive tubes

have blue band

Smaller microhematocrit

designed for use with special microcentrifuges, such as those available from StatSpin, Inc. (Norwood, MA)

Smaller microhematocrit

often used in infant and child anemia screening programs and pediatric clinics

Plastic or clay sealants

come in small trays are used to seal one end of microhematocrit tubes

Plastic or clay sealants

dry end of the tube was inserted into the clay to plug it

• CBG collection tubes

• Stirrers

• Magnet

• Plastic caps

following special equipment (Fig. 8-5) is used to collect capillary blood gas (CBG) specimens:

CBG collection tubes

long thin narrow-bore capillary tubes

most common CBG tubes

100 mm in length with a capacity of 100 uL

color-coded band

identifies the type of anticoagulant that coats the inside of the tube;

Stirrers

small metal filings (often referred to as “fleas”)

Stirrers

small metal bars that are inserted into the tube after collection of a CBG specimen to aid in mixing the anticoagulant

Magnet

Both ends of a CBG tube are sealed immediately after specimen collection to prevent exposure to air, and a magnet is used to mix the specimen.

Magnet

typically has an opening in the center or side so that it can be slipped over the capillary tube and moved back and forth along the tube length

Plastic caps

used to seal CBG tubes and maintain anaerobic conditions in the specimen

CBG tubes

typically come with their own caps

Glass microscope slides

occasionally used to make blood films for hematology determinations

Warming the site

increases blood flow as much as seven times

Warming the site

especially important when performing heelsticks on newborns

Heel-warming devices

are commercially available

To avoid burning the patient,

the devices provide a uniform temperature that does not exceed 42°C

A towel or diaper dampened with warm tap water

can also be used to wrap a hand or foot before skin puncture

Capillary specimens

mixture of arterial, venous, and capillary blood, along with interstitial fluid (fluid in the tissue spaces between the cells) and intracellular fluid (fluid within the cells) from the surrounding tissues

Because arterial blood enters the capillaries under pressure,

capillary blood contains a higher proportion of arterial blood than venous blood

warming

increases arterial flow into the area

reference (normal) values may also differ

Because the composition of capillary blood differs from that of venous blood,

concentration of glucose

normally higher in capillary blood specimens

total protein (TP), calcium (Ca2+), and potassium (K+ )

concentrations are lower

small amounts of blood are acceptable for testing

properly collected capillary specimen can be a practical alternative to venipuncture when

o Available veins are fragile or must be saved for other procedures such as chemotherapy.

o Several unsuccessful venipunctures have been performed and the requested test can be collected by capillary puncture.

o The patient has thrombotic or clot-forming tendencies.

o The patient is apprehensive or has an intense fear of needles.

o There are no accessible veins (e.g. the patient has IVs in both arms or the only acceptable sites are in scarred or burned areas).

o To obtain blood for POCT procedures such as glucose monitoring

Capillary puncture can be an appropriate choice for adults and older children under the following circumstances:

Capillary puncture

preferred method of obtaining blood from infants and very young children

4 mg of iron is also removed

for every 10 mL of blood removed, as much as

Large quantities removed rapidly

can cause cardiac arrest

Obtaining blood from infants and children by venipuncture

difficult and may damage veins and surrounding tissues

Puncturing deep veins

can result in hemorrhage, venous thrombosis, infection, and gangrene

An infant or child

can be injured by the restraining method used while performing a venipuncture

Capillary blood

the preferred specimen for some tests, such as newborn screening tests

specimens may be hard to obtain and may not be representative of blood elsewhere in the body

Capillary puncture is generally not appropriate for patients who are dehydrated or have poor circulation to the extremities from other causes, such as shock, because

erythrocyte sedimentation rate methods, coagulation studies that require plasma specimens, blood cultures, and tests that require large volumes of serum or plasma

tests that cannot be collected by capillary puncture

light blue top microtubes

not to be used for capillary specimens. They are intended to be used for venous blood collected by syringe in difficult draw situations

order of draw for collecting multiple specimens by capillary puncture

not the same as for venipuncture

Puncturing the skin

releases tissue thromboplastin, which activates the coagulation process in the blood drops

Specimens must be collected quickly

to minimize the effects of platelet clumping and microclot formation and to ensure that an adequate amount of specimen is collected before the site stops bleeding

Hematology specimens

e collected first because they are most affected by the clotting process

Serum specimens

collected last because they are supposed to clot

• Blood gas specimens (CBGs)\

• EDTA specimens

• Other additive specimens

• Serum specimens

CLSI order of draw for capillary specimens is as follows:

Specimens for newborn screening tests

should be collected separately

Position is important

patient comfort and the success of specimen collection

finger punctures

firm surface with the hand extended and palm up.

heel punctures

infant should be supine (lying face up) with the foot lower than the torso so the force of gravity can assist blood flow

o warm,

o pink or normal color,

o free of scars, cuts, bruises, or rashes.

o It should not be cyanotic (bluish in color), edematous (swollen), or infected.

General site selection criteria include one that is

Swollen or previously punctured sites

should be avoided, because accumulated tissue fluid can contaminate the specimen and negatively affect test results

Specific locations for capillary puncture

include fingers of adults and heels of infants

palmar surface of the distal or end segment of the middle or ring finger of the nondominant hand

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

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

puncture site should be in

under 1 year of age

According to CLSI standards, capillary puncture must not be performed on the fingers or earlobes of newborns or other infants

• Do not puncture fingers of infants and children under 1 year of age

• Do not puncture fingers on the same side as a mastectomy

• Do not puncture parallel to the grooves or lines of the fingerprint

• Do not puncture the fifth or little (pinky) finger.

• Do not puncture the index finger.

• Do not puncture the side or very tip of the finger.

• Do not puncture the thumb.

FINGER PUNCTURE PRECAUTIONS

heel

recommended site for collection of capillary puncture specimens on infants less than 1 year of age

little risk of puncturing the bone

important to perform the puncture in an area of the heel where there is

• Osteomyelitis

• Osteochondritis

Puncture of the bone can cause painful:

Osteomyelitis

inflammation of the bone marrow and adjacent bone

Osteochondritis

inflammation of the bone and cartilage, as a result of infection

can spread an infection

Additional punctures through a previous puncture site that is inflamed

may be as little as 2.0 mm

calcaneus or heel bone of small or premature infants

may cause bone damage

Punctures deeper than this

dermal–subcutaneous junction between 0.35 and 1.6 mm

vascular or capillary bed (Fig. 8-8) in the skin of a newborn is located at the

punctures 2.0 mm deep or less

will provide adequate blood flow without risking bone injury

plantar surface of the heel, medial to an imaginary line extending from the mid

According to CLSI, to avoid puncturing bone the only safe areas for heel puncture are on the

bone, nerve, tendon, and cartilage injury

Punctures in other areas risk

medial or lateral plantar surfaces of the heel

safe areas for heel puncture are

• Do not puncture any deeper than 2.0 mm

• Do not puncture areas between the imaginary boundaries

• Do not puncture in the arch and any areas of the foot other than the heel

• Do not puncture severely bruised areas

• Do not puncture the posterior curvature of the heel

• Do not puncture through previous puncture sites

• Do not puncture a site that is swollen

HEEL PUNCTURE PRECAUTIONS

PaO2 levels

does not significantly alter results of routinely tested analytes

Increased blood flow

makes specimens easier and faster to obtain and reduces the tendency to compress or squeeze the site

arterialized

a specimen obtained from a warmed site is described as being

warming the site

is essential when collecting capillary pH or blood gas specimens.

Warming

recommended for heelstick procedures

wrapping the site for 3 to 5 minutes with a washcloth, towel, or diaper

Warming can be accomplished by

42°C (108°F)

temperature of the material used to warm the site must not exceed

skin flora (microorganisms on the skin) do not infiltrate the puncture wound and cause infection

collection site must be cleaned with an antiseptic before puncture

70% isopropanol

CLSI-recommended antiseptic for cleaning a capillary puncture site

: Do not use povidone–iodine to clean skin puncture sites

greatly interferes with a number of tests, most notably bilirubin, uric acid, phosphorus, and potassium

“BURPP”

• bilirubin

• uric acid

• phosphorus

• potassium

tests affected by povidone–iodine