Capillary Blood Composition and Dermal Puncture

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.

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.