Capillary Puncture: Equipment, Order of Draw & Procedures

What are lancets and incision devices used for?

They are sterile, single-use automated devices engineered to puncture or incise cutaneous tissue.

What safety standards do lancets comply with?

They comply with Occupational Safety and Health Administration (OSHA) safety standards to prevent accidental needlestick injuries.

What is the purpose of microcollection containers?

They are intended for collecting small volumes of whole blood, serum, or plasma via skin puncture.

What does a pink/lavender cap on a microcollection container indicate?

It indicates the presence of potassium ethylenediaminetetraacetic acid (EDTA) for hematology testing.

What is the function of a green cap on a microcollection container?

It contains lithium heparin anticoagulant for plasma chemistry evaluations.

What is the purpose of microhematocrit tubes?

They are used primarily for measuring packed cell volume (hematocrit).

What are capillary blood gas (CBG) equipment used for?

They are used for collecting and analyzing capillary blood gases.

What is the maximum temperature for warming devices used before skin puncture?

The maximum temperature is regulated at ≤ 42 °C to avoid thermal injury.

What components make up capillary blood?

Capillary blood consists of arterial blood, venous blood, interstitial fluid, and intracellular fluid.

Why are glucose levels higher in capillary blood compared to venous blood?

Because of rapid metabolic extraction of glucose across tissue capillary beds.

What are some clinical indications for capillary puncture?

Indications include fragile veins, point-of-care testing, and blood collection in infants.

What is a contraindication for capillary puncture?

Severe dehydration, which compromises peripheral capillary beds and sample yield.

Why are blood cultures incompatible with capillary puncture?

Skin puncture carries a high rate of surface microbial contamination.

What tests are affected by capillary puncture due to tissue factor release?

Coagulation tests like Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT).

What is the order of draw for capillary specimens?

Capillary Blood Gas specimens first, followed by EDTA specimens, other additive specimens, and serum specimens last.

What should be avoided during capillary blood collection?

Avoid milking or forcefully squeezing the collection site to prevent hemolysis.

What are the recommended puncture areas for fingersticks in adults and children over 1 year?

The palmar surface of the distal phalanx of the middle or ring finger.

Why should the thumb be avoided for fingerstick punctures?

It contains an identifiable arterial pulse and has a thicker epidermal stratum.

What is the purpose of warming devices before a skin puncture?

They induce local vasodilation and increase peripheral blood flow.

What does a red cap on a microcollection container indicate?

It indicates no additive or a plain silicone-coated interior for serum testing.

What is the function of a gold/yellow cap on a microcollection container?

It contains a clot activator and gel separator for serum separation.

What are the two types of microhematocrit tubes?

Non-heparinized (plain, blue band) and heparin-coated (red band) tubes.

What is the role of metal stirrers in capillary blood gas collection?

They facilitate thorough mixing of anticoagulant with blood while excluding air bubbles.

What is the significance of capillary blood resembling arterial blood?

Because arterial capillary pressure exceeds venous pressure, capillary blood closely resembles arterial blood in composition.

What is the effect of dilution by interstitial fluid on capillary blood composition?

It accounts for lower concentrations of large protein molecules and bound electrolytes.

What is the impact of severe localized edema on capillary puncture?

It dilutes the blood sample with excess tissue fluid, compromising sample quality.

What is the importance of avoiding mechanical compression during sample collection?

Mechanical compression can cause hemolysis and contamination of the sample.

What is the risk associated with the fifth (pinky) finger during capillary puncture?

High risk of hitting the phalanx due to insufficient subcutaneous tissue distance from skin to underlying digital bone.

What is the significance of the distal tip center of the finger in capillary puncture?

It contains dense nerve terminal endings and has reduced subcutaneous cushioning.

Why should incisions be placed perpendicular to fingerprint ridges?

To allow blood to pool into a high, compact droplet.

What are the recommended puncture areas for heelsticks in infants under 1 year of age?

The medial and lateral plantar surfaces of the heel.

What boundary lines define the safe puncture areas on an infant's heel?

Imaginary lines from the center of the great toe to the posterior heel margin and between the fourth and fifth toes to the posterior heel margin.

What site should be avoided during heelstick procedures?

The plantar arch of the foot due to the risk of severing arteries and nerves.

What is the depth of the calcaneus below the epidermal surface?

Less than 2.0 mm, posing a risk for bone perforation.

What is the first step in the capillary puncture procedure?

Confirm medical orders and identify the patient using at least two identifiers.

Why is it important to allow the disinfectant to air-dry completely before puncture?

Wet alcohol can cause chemical hemolysis and alter blood test parameters.

What should be done with the first drop of blood after a capillary puncture?

Wipe it away using a sterile, dry gauze pad to avoid skewed diagnostic accuracy.

What is the purpose of applying gentle, intermittent pressure during blood collection?

To facilitate blood flow without causing hemolysis or hemodilution.

What is the mandatory protective step during neonatal bilirubin testing?

Collect in light-blocking amber-tinted tubes or wrap in aluminum foil to prevent photo-degradation.

What is the purpose of the Newborn Screening (NBS) test?

To detect critical metabolic and inherited conditions in newborns.

What are the conditions typically detected by Newborn Screening?

Phenylketonuria (PKU), Cystic Fibrosis (CF), Congenital Hypothyroidism, and Galactosemia.

What is the procedure for preparing a thick blood smear for malaria screening?

Apply a large drop of capillary blood onto a slide and spread it to the size of a dime.

What are the safety precautions regarding sharps during capillary puncture?

Use OSHA-compliant, single-use, retractable lancets and never reuse skin puncture devices.

What complications can arise from excessive mechanical squeezing during blood collection?

Hemolysis and hemodilution due to the introduction of interstitial fluid.

Why should adhesive bandages not be applied to infants under 2 years old?

Risk of severe skin tearing and choking hazards if the bandage is removed and placed in the mouth.

What is calcaneal osteomyelitis?

A serious bone infection caused by deep penetration of a lancet into the calcaneus.

What is the risk of nerve laceration during capillary puncture?

Injury sustained by puncturing anatomical high-risk zones, such as the plantar nerve tracks.

What is the recommended temperature for warming the puncture site?

Up to 42°C for 3-5 minutes to optimize capillary blood flow.

What should be done immediately after collecting blood in anticoagulant-containing microtubes?

Invert gently 8-10 times to prevent microclot aggregation.

What is the consequence of puncturing previously punctured sites?

Increased risk of infection and contamination of samples.

What is the purpose of immobilizing the patient's hand or heel during the procedure?

To prevent sudden movement that could lead to complications.

What should be done with biohazardous materials after the procedure?

Properly dispose of all materials and used protective equipment.