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Capillary punctures
| Question | Answer |
|---|---|
| Describe the recommended boundaries/area to perform capillary puncture from an infant patient | • Plantar surface of the heel, • Medial to an imaginary line extending from middle of big toe to the heel OR • Lateral to an imaginary line extending from between the 4th and 5th toe to the heel |
| What is the rationale for: Do not puncture fingers of children under one year old | Amount of skin between skin surface and bone is so small that bone injury is likely |
| What is the rationale for: Do not puncture the index finger | It is more sensitive, therefore more painful, and is more calloused |
| What is the rationale for: Do not puncture the thumb | It has a pulse and the skin is thick and calloused |
| What is the rationale for: Do not puncture the side or tip of the finger | The distance between skin and bone is half as much as the tissue between the fleshy central portion of the finger |
| What is the rationale for: Do not puncture parallel to the grooves of the finger prints | Makes blood collection difficult, as blood does not form a rounded drop |
| What is the rationale for: Do not puncture the “pinky”/ little finger | Tissue between skin and bone is thinnest in this finger, making bone injury more likely |
| Do not puncture the posterior curve of the heel because: | The bone can be as little as 1mm deep - bone injury |
| Do not puncture in the arch of the foot because: | Arteries, nerves and tendons may be damaged |
| List 4 blood tests that cannot be performed by skin puncture | • ESR • Blood culture • Coagulation studies • Tests requiring larger volumes of serum or plasma |
| Describe THREE ways you can prevent a capillary specimen from haemolysing during collection | Don't excessively squeeze or milk the puncture site to obtain blood. Allow alcohol to air dry completely before making a puncture. Don't prick a haematoma site or swollen site. Wipe away the first drop of blood to prevent tissue fluid contamination |
| Explain the technique errors that could make the collection of capillary blood difficult | •Didn't warm site •Didn't allow alcohol 2dry •Didn't make proper cut •Didn't squeeze correct •Didn't release 2 allow capillaries 2 fill •Didn't wipe away plts from edge of wound •Didn't cut across finger print •Didn’t lower heel to help blood flow |
| Explain rules to consider when collecting a dermal sample for a newborn metabolic screening test using a Guthrie card | •Filter paper mustn't touch heel •A large drop of blood must completely fill each of the demarcated circle •Blood to soak through both sides of paper •Allow specimen to air-dry before packing •Don't contaminate card with gloves, fingers, alcohol |
| List causes of how a phlebotomist could potentially infect a dermal puncture site | • Use of non-sterile or contaminated equipment • Poor aseptic technique • Using an infected site • Using a previously punctured site |
| Where would you perform a capillary puncture on an adult? | Palmer surface of the distal/ end segment, on the fleshy pad of the middle and ring finger of non-dominant hand perpendicular to whorls of the fingerprint |
| When doing a heel puncture: Do not puncture any deeper than 2mm because | Deeper punctures risk injuring bone even in the safest puncture areas |
| When doing a heel puncture: Do not puncture severely bruised areas | It is painful, and impaired circulation or by-products of healing can negatively affect the specimen |
| When doing a heel puncture: Do not puncture through previous puncture sites | This can be painful and can spread infection |
| When doing a heel puncture: Do not puncture a site that is swollen | Excess tissue fluid in the area could contaminate the specimen |
| When doing a heel puncture: Do not puncture areas between imaginary boundaries | The calcaneus may be as little as 2mm deep in that area |
| List nine finger prick sites that are not recommended and explain why the site is not recommended | •fingertip-close2bone •Parallel2fingerprints-no round drop •Index finger-hard skin, sensitive •Little finger-less tissue •Infantsfingers-less tissue •Thumb–pulse •Oedematous–tissue fluid •Previously punct–old blood •Infected–infect •Mastectomy- |
| Describe ways you can cause a capillary specimen to haemolyse during collection | •Excessive squeezing of puncture site or “milking” site to obtain enough blood. •The presence of Isopropyl 70% alcohol on the skin i.e. the skin was not allowed to dry before it was punctured •Pricking a haematoma site •Scraping tube against the skin |
| Describe a common cause of bruising a patient during a capillary puncture | Squeezing the site too hard |
| Name problems that may happen if you repeatedly collect capillary specimens from the same site | • The site may become infected • It is more painful for the patient • Old blood will get into the sample giving an incorrect result |
| Explain why you cannot collect capillary blood from an oedematous site | Because the tissue fluid will dilute the sample and give erroneous results |
| When obtaining a capillary sample for a newborn screening test, care must be taken not to contaminate the Guthri card with........? | Glove powder....Urine from the infants diaper.....Alcohol Residue |
| Why may coagulation studies not be performed on dermal blood? | Because puncturing the skin releases tissue thromboplastin which activates the coagulation process and will negatively affect coagulation results |
| List indications for dermal puncture in adults | • Fragile veins • POC • Intense fear of needles • No access to veins • Pt has clot forming tendencies • Several unsuccessful venipuncture’s |
| Briefly describe the composition of capillary blood | Is a mixture of both venous and arterial blood |
| What is the acceptable age group for doing dermal/heel prick on babies? | Birth to 1 year old |
| Explain how the patients arm needs to be positioned prior to dermal puncture | • the arm must be supported on a firm surface • with the hand extended and palm facing up |
| List the order of draw for the dermal puncture procedure | • Blood gas (if requested) • EDTA • Other additive tubes • Gel/ non additive tubes |
| Name one tube that may not be used in dermal puncture AND give your reason | • Citrate tube/ blue top tube • Because you may not obtain blood for coagulation studies by dermal puncture. As soon as a dermal cut is made, tissue thromboplastin will be released & activate the coagulation cascade - influencing any coagulation results |
| List items of equipment you would assemble in preparation for a dermal puncture procedure | •Warming device •70% Isopropyl alcohol •gauze •adhesive plaster •Capillary tubes •Lancet •Microtainer tubes •POC device |
| Why is it important to warm the site prior to dermal puncture? | Increases blood flow by 7 fold |
| Give the reason for wiping away the first drop of blood when doing a dermal puncture | • Prevents contamination of tissue fluid and residual alcohol |
| What could the consequence be to puncturing the heel bone of a baby? | Osteomyelitis/ osteochondritis |
| Where in relation to the whorls of the finger print must the puncture be made with the lancet? Give the reason for your answer | • Perpendicular to the whorls • To facilitate a rounded drop of blood to form, thus making collection easier |
| Explain rules to consider when collecting a dermal sample for a newborn metabolic screening test using a Guthrie card | •filter paper must not touch the heel •A large drop of blood must completely fill each demarcated circle •blood must soak through both sides of paper •specimen to air-dry before packing •Dont contaminate card with gloves, fingers, alcohol |
Created by:
cisca