Capillary Collection (Chapter 10)

Vocabulary flashcards covering terminology, devices, sites, prep rules, and procedures related to capillary collection.

Capillary collection

Collection of blood by skin puncture (capillary/dermal puncture) when venipuncture is difficult or for populations like newborns; yields a mix of arterial/venous blood with some tissue fluid.

Skin puncture (dermal puncture)

Inserting a lancet into the skin to obtain capillary blood; depth and width are controlled; first drop is managed to avoid contamination.

Capillary blood gas (CBG)

Capillary blood used to determine gas levels as an alternative to arterial blood gas (ABG); results may differ from arterial samples.

Capillary vs arterial/venous blood composition

Capillary blood is a mix of venous and arterial blood; warming increases arterial proportion; contains small amounts of tissue fluid; not all tests yield identical results to venous samples.

First drop rule

Wipe away the first drop of capillary blood to stop contamination and dislodge platelet plugs; helps prevent inaccurate test results.

Povidone-iodine cautions

Not recommended for prep of capillary puncture sites because it can elevate test results.

Warming device

Tool used to warm the puncture site to increase capillary blood flow and arterial component.

Lancet

A sharp puncturing device for skin puncture; may be automatic with adjustable depth and color-coded platforms; safety features may include retractable blades.

Heel incision device

Neonatal devices designed for heel punctures (often with sweeping technique) to access capillary beds safely.

Lasette

Laser lancing device with a single-use lens for capillary punctures in patients aged 5 years and older.

Microsample container

Container designed to hold very small volumes of capillary blood collected via microsample tubes.

Microcollection tubes

Small plastic tubes with anticoagulants or additives; color-coded to match with evacuated tubes and used for dermal puncture samples.

Microhematocrit tubes

Tiny capillary tubes used to hold small volumes of capillary blood for micro-sampling and neonatal screening.

Dried blood spot (DBS)

Blood samples collected on filter paper and dried; used in neonatal screening and certain tests.

Capillary tubes color codes

Tubes come plain (blue band) or anticoagulant-coated (red, yellow, green bands) indicating additives.

Caraway pipet

Narrow plastic capillary tubes used to carry small volumes of capillary blood during collection.

Natelson pipet

Another type of capillary collection tube used for small-volume capillary blood; sizes vary.

Capillary collection sites – adults/older kids

Typically nondominant hand fingertips (3rd and 4th digits) on the palmar side; puncture near the center of the finger, perpendicular to fingerprint ridges.

Capillary collection sites – infants

For babies under ~6 months, heel puncture is preferred; puncture on medial/lateral sides of the heel to avoid bone.

Puncture depth recommendations

Depth depends on site; lancet depth generally ≤3.0 mm; heel puncture ≤2.0 mm; premature infant depth around 0.65–0.85 mm.

Puncture width significance

Width of the puncture can be more important than depth because capillary beds lie near the surface; wider cuts improve blood flow with less nerve injury.

Mastectomy site considerations

For mastectomy patients, perform capillary puncture on the opposite side unless otherwise allowed, to avoid lymphedema risk.

Capillary blood usage (glucose/ABG)

Capillary blood can be used for bedside glucose testing and as an alternative to arterial puncture for ABG determinations.

Bleeding time (BT) vs PFA

Bleeding time test measures time to stop bleeding and has largely been replaced by platelet function assays (PFA) using venous blood.

Tissue fluid contamination risk

Capillary samples can be contaminated by tissue fluid from the puncture site; wipe first drop and avoid excessive squeezing.

70% isopropyl alcohol use

70% isopropyl alcohol is used to clean certain tests (e.g., bilirubin, uric acid, phosphorus, potassium) before sampling.