Capillary Blood Composition and Dermal Puncture

Questions and Answers

What does the composition of capillary blood include?

Arterial

Neither

Both venous and arterial (correct)

Venous

Dermal punctures may be best for which of the following patients? (Select all that apply)

Geriatric patients (correct)

Obese patients (correct)

Children (correct)

Adult males

Situations that may require dermal punctures include which of the following? (Select all that apply)

Patients at risk for arteriospasm or cardiac arrest (correct)

Patients with orders for only one blood test (correct)

Patients with multiple prescriptive medications

Patients on IV therapy (correct)

Which tests can be performed on blood collected by dermal puncture?

BUN Signup and view all the answers

Which analytes are typically higher in venous blood than capillary blood? (Select all that apply)

Potassium Signup and view all the answers

What impact does switching from venous sampling to dermal punctures during a glucose tolerance test have?

Compromises the test interpretation because venous glucose levels are lower than capillary levels. Signup and view all the answers

What equipment is required for dermal puncture sample collection for bilirubin testing on a newborn? (Select all that apply)

Lancet Signup and view all the answers

What controls the dimensions of a dermal puncture?

Width, depth of the blade Signup and view all the answers

Which features are characteristic of dermal puncture devices? (Select all that apply)

Single use Signup and view all the answers

What does the term 'bullet' in blood collection refer to?

Microcollection tubes Signup and view all the answers

What is used when collecting a Natelson pipette?

A flea or metal filing Signup and view all the answers

What is a dilution system used for cell counts in hematology?

Unopette Signup and view all the answers

What is the maximum temperature that any warming device for dermal punctures should not exceed?

42° C Signup and view all the answers

What is needed when collecting a Caraway micropipette?

Plastic caps Signup and view all the answers

Which are characteristics of a good dermal site? (Select all that apply)

Absence of scars Signup and view all the answers

What should the phlebotomist ensure during a dermal puncture to avoid puncturing the calcaneus?

Automatic device does not puncture the heel Signup and view all the answers

What could result from puncturing the bone during a dermal puncture procedure?

Osteomyelitis Signup and view all the answers

What is the puncture depth of a device used for dermal puncture on a preemie?

0.65 to 0.85 mm Signup and view all the answers

What is the maximum depth of puncture for a heelstick?

2.0 mm Signup and view all the answers

What should the width of a puncture not exceed?

2.4 mm Signup and view all the answers

Why does puncture width play an important role in establishing blood flow in a dermal stick?

A wider cut severs more capillaries Signup and view all the answers

Dermal puncture sites in adults and children older than 1 year include which of the following? (Select all that apply)

Middle finger Signup and view all the answers

When performing a dermal puncture on the finger, where should the puncture be made?

Perpendicular to the fingerprint ridges Signup and view all the answers

Why are dermal punctures performed on heels for children younger than 1 year?

There is too little flesh on the fingers Signup and view all the answers

Dermal puncture sites on an infant include all of the following: (Select all that apply)

Plantar surface of the big toe Signup and view all the answers

What determines the selection of the type of skin puncture device?

Age of the patient Signup and view all the answers

What does the acronym BURPP represent?

A collection of tests that cannot be performed using povidone-iodine. Signup and view all the answers

In which order should specimens be collected for H & H, BUN, and creatinine?

Lavender, Gold Signup and view all the answers

Which represents proper dermal puncture technique on an adult? (Select all that apply)

Selecting middle or ring finger Signup and view all the answers

Why must the first drop of blood be wiped away after the puncture?

Prevent tissue fluid contamination Signup and view all the answers

What is involved in the proper collection of microcollection tubes? (Select all that apply)

Tapping lightly to move blood into the tube Signup and view all the answers

Why did the CBC have to be recollected for a lethargic, febrile newborn?

The specimen spilled when the aspirating needle displaced the extra blood Signup and view all the answers

Why should bandages not be applied on children under the age of 2 years?

They can pull it off and may choke on it Signup and view all the answers

What is the proper technique for filling a hematocrit?

Touching the drop and letting it fill by capillary action Signup and view all the answers

What is the screening test that involves the vascular system and platelet function?

Bleeding time Signup and view all the answers

What is the normal range for bleeding time results?

2 to 10 minutes Signup and view all the answers

What might indicate an abnormal bleeding time test? (Select all that apply)

Skin condition Signup and view all the answers

What orientation of the blade produces the most accurate results in a bleeding time test?

Parallel to the antecubital crease Signup and view all the answers

What pressure should the blood pressure cuff be inflated to during a bleeding time?

40 mm Hg Signup and view all the answers

When does the phlebotomist start the timer during a bleeding time test?

Simultaneously as she presses the trigger Signup and view all the answers

What is included in the proper technique for wicking away the blood during a bleeding time? (Select all that apply)

Continue to wick until the drop disappears Signup and view all the answers

What must the phlebotomist ensure before performing ancillary blood glucose testing?

Running controls the same as patient samples Signup and view all the answers

Study Notes

Capillary Blood Composition

Capillary blood consists of venous and arterial blood components.

Ideal Candidates for Dermal Puncture

Dermal punctures are suitable for children, geriatric patients, and obese individuals.

Situations Indicating Dermal Punctures

Recommended for patients on IV therapy, those requiring only a single blood test, and patients at risk for cardiac complications.

Tests Feasible via Dermal Puncture

Blood urea nitrogen (BUN) can be tested using samples obtained from dermal punctures.

Analyte Levels in Blood

Potassium, calcium, and total protein levels are generally higher in venous blood compared to capillary blood.

Impact of Switching to Dermal Puncture During Glucose Test

Using dermal samples for a glucose tolerance test may compromise results since capillary glucose levels are higher than venous levels.

Equipment for Newborn Bilirubin Testing

Essential tools for bilirubin tests include a lancet, an amber-colored microtainer tube, and a warming device.

Controlling Dermal Puncture Depth

Depth and width of the puncture are critical factors in dermal punctures.

Features of Dermal Puncture Devices

Modern devices have a retractable blade, are single-use, and feature automatic puncturing mechanisms.

Blood Collection Terminology

"Microcollection tubes" are often referred to as "bullets."

Special Collection Tools

A flea or metal filing is used for collecting samples with a Natelson pipette.

Dilution System for Hematology

The Unopette system is utilized for cell count dilutions.

Safe Temperature for Warming Devices

Warming devices used during dermal punctures should not exceed 42°C.

Additional Equipment for Micropipette Collection

Plastic caps are necessary for Caraway micropipette collections.

Characteristics of Good Dermal Puncture Sites

An effective dermal site should demonstrate good venous flow.

Avoiding Bone Damage During Dermal Punctures

When puncturing the heel, care must be taken to avoid the calcaneus bone.

Consequences of Bone Puncture

Puncturing a bone during the procedure can lead to osteomyelitis, an infection of the bone or marrow.

Appropriate Puncture Depth for Preemies

Suitable devices for dermal punctures on premature infants should have a puncture depth of 0.65 to 0.85 mm.

Maximum Puncture Depth for Heelsticks

The maximum allowable depth for heelsticks is 2.0 mm.

Puncture Width Specifications

The width of a dermal puncture should not exceed 2.4 mm.

Importance of Puncture Width

A wider puncture enhances blood flow by severing more capillaries.

Dermal Puncture Sites in Older Children

Acceptable puncture sites for children older than one include the middle finger, big toe, and ring finger.

Technique for Finger Puncture

Punctures on the finger should be made perpendicular to the fingerprint ridges.

Infants' Dermal Puncture Site Considerations

Derma punctures in infants under one year are preferentially performed on the heel due to minimal flesh on fingers.

Proper Infant Dermal Puncture Sites

Acceptable puncture locations for infants include medial and lateral borders of the plantar surface, as well as the plantar surface of the big toe.

Device Selection Criteria

The choice of skin puncture device hinges on the patient's age.

BURPP Test Considerations

The BURPP acronym denotes tests that cannot be performed using povidone-iodine.

Collection Order for Blood Tests

For collecting H&H, BUN, and creatinine, the order is lavender followed by gold.

Proper Dermal Puncture Techniques

Correct technique includes selecting the middle or ring finger, making cuts perpendicular to fingerprints, and wiping away the first blood drop.

Importance of Wiping First Blood Drop

The initial drop of blood is wiped away to prevent contamination from tissue fluid.

Techniques for Microcollection Tubes

Proper technique involves touching the scoop to blood, allowing it to flow freely, and gently tapping it to move the blood into the tube.

Possible Collection Failure

An extra blood spill during a CBC due to an aspirating needle displacing the sample necessitated recollection.

Bandage Safety for Young Children

Bandages are not recommended for children under two years due to choking hazards.

Hematocrit Collection Technique

Hematocrit tubes should be filled via capillary action by touching the drop.

Screening Tests for Hemostasis

Bleeding time tests assess the vascular system and platelet function for primary hemostasis integrity.

Normal Bleeding Time Range

Typical bleeding time results should fall between 2 to 10 minutes.

Causes of Abnormal Bleeding Time

An abnormal test can suggest platelet disorders, skin conditions, or medication interferences.

Bleeding Time Test Blade Orientation

The blade should be parallel to the antecubital crease for the most accurate bleeding time results.

Blood Pressure Cuff Pressure for Bleeding Time

Maintain a pressure of 40 mm Hg when inflating the blood pressure cuff.

Wicking Technique During Bleeding Time

Proper wicking involves touching filter paper to the drop, repeating every 30 seconds until the drop vanishes.

Pre-testing Protocol for Blood Glucose Devices

Ensure the performance of the instrument by running controls alongside patient samples before commencing glucose testing.

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Description

Explore the nuances of capillary blood composition, ideal candidates for dermal puncture, and the various situations where this method is beneficial. Learn about the tests that can be done and the implications of using dermal samples in specific tests, particularly in relation to glucose measurements.