1. Chapter 10
Dermal Puncture

2. Learning Objectives
List situations in which a dermal puncture might be preferred.
Explain why it is necessary to inform the physician when capillary blood is collected.
Describe skin puncture devices, including safety features they may have.
Discuss containers that may be used to collect capillary blood.

3. Learning Objectives List the steps in the BD Unopette dilution method.
Explain how circulation may be increased at the puncture site.
Discuss proper dermal puncture site selection.
Explain why it is important to control the depth of the puncture.

4. Learning Objectives List in order the steps for dermal puncture.
Describe how the cut should be made when a finger is used.
Explain why the first drop of blood is discarded.
List precautions to be observed when collecting capillary blood.
State the order of draw in collecting capillary blood.

5. Learning Objectives Explain the use of the bleeding time test.
List the equipment required to perform a bleeding time test.
List in order the steps for performing a bleeding time test.
Explain the procedure for performing a bedside glucose test.

6. Dermal Puncture
Dermal puncture is an alternative collection procedure when small amounts of blood are needed, or when venipuncture is inadvisable or impossible.
It is the usual collection procedure for infants and children under 2 yrs. of age.
It is also used for bleeding times, ancillary blood glucose testing, and obese patients.
In most cases it will be up to the phlebotomist to decide whether or not a dermal puncture is the best choice for blood collection.

7. Dermal Puncture
It is used for geriatric patients, those at risk for venous thrombosis, and those with burns or scars over venipuncture sites.
It is also used for patients with only one test ordered, those receiving IV therapy, frequent blood tests, and those who might be at risk for injury from restraints that might be needed for a venipuncture.
Reducing blood volume through venipuncture is a concern for all children. It may lead to anemia and even cardiac arrest and death. Many patients may be saving veins for chemotherapy procedures also.

8. Dermal Puncture
Dermal punctures cannot be done for blood cultures, sed rates and coagulation tests.
It should not be done on dehydration patients or those in shock, or on sites that are swollen or where circulation is compromised such as in a mastectomy.

9. Venous vs. Capillary Blood
Capillary blood is a mixture of arterial blood, venous blood, and tissue fluid. It is more arterial when warmed.
Hemoglobin and glucose values are higher in capillary blood.
Potassium, calcium, and total protein values are higher in venous blood.
It is important to use the same method of collection for repeat testing on the same patient for glucose, potassium, hemoglobin, calcium and total protein.

10. Skin Puncture Devices
Skin puncture devices come in different types and sizes to meet different needs.
To meet safety regulations, devices now have retractable blades that lock to prevent being used a second time.
The phlebotomist will decide which device will work best for the site selected. Have samples to show students.
Courtesy of Zack Bent.  From Garrels M, Oatis CS: Laboratory Testing for Ambulatory Settings: A Guide for Health Care Professionals.  Philadelphia, Saunders, 2006.

11. Microsample Containers
Containers come in microcollection tubes, capillary tubes, and micropipets.
The phlebotomist needs to know how much blood is needed to be able to pick the correct container. Have samples to show students.
Courtesy of Zack Bent.  From Garrels M, Oatis CS: Laboratory Testing for Ambulatory Settings: A Guide for Health Care Professionals.  Philadelphia, Saunders, 2006.

12. Dermal Puncture
Warming devices will increase capillary circulation and blood flow.
Wash cloths or commercial heel warmers can be used.
Temperature should not exceed 42o C and should be applied for 3 to 5 minutes.
Make sure that sites are dry before puncturing. Water will cause hemolysis and dilution of the sample.

13. Dermal Puncture Width and Depth
Depth should not exceed 2.0 mm in infant heels; 0.65 to 0.85 mm in premature infants.
Care should be taken to not puncture the calcaneus (heel) bone.
A wider puncture cut will increase blood flow, but puncture width should not exceed 2.4 mm.
Bone puncture can lead to osteochondritis, inflammation of the bone or cartilage or osteomyelitis, a potentially serious, sometimes fatal, bone infection.

14. Dermal Puncture Sites in Adults & Older Children
Punctures should be done on the palmar surface of the distal segments of the middle or ring finger of the nondominant hand.
Punctures with blades should be made perpendicular to the ridges in the fingers to keep the blood from flowing into the grooves.
The thumb should not be used since it may be calloused and contains an artery. The index finger is usually more sensitive because of the extra nerve endings. The little finger has too little tissue for a safe puncture. The big toe may also be used. Never use earlobes.

15. Dermal Puncture in Infants
For infants under one year old and not walking, use the medial or lateral portion on the plantar (bottom) surface of the heel.
The center of the heel and back of the heel are too close to the calcaneus bone to be used. The arch should not be used since it is too close to nerves and tendons. The big toe may be used.

16. Dermal Puncture Procedure
Follow standard precautions making sure to wash hands and put on gloves.
Always greet patient and parents, if present, obtain consent, and identify patient as you would for a venipuncture.
On inpatient infants, the armband may be on the ankle.

17. Dermal Puncture Procedure
Document on the requisition that you are performing a dermal puncture.
Assemble your equipment.
Use the patient age, size and tests ordered to determine puncture device needed.
Select and clean the site, warming first, then cleaning with 70% isopropyl alcohol.
Make sure that alcohol is dry before making the puncture so as not to sting the patient or cause hemolysis or contamination of the specimen. Use of povidone iodine is not recommended because it can cause false elevation of bilirubin, uric acid, phosphorus, and potassium (BURPP).

18. Dermal Puncture Procedure
Courtesy of Zack Bent.  From Garrels M, Oatis CS: Laboratory Testing for Ambulatory Settings: A Guide for Health Care Professionals.  Philadelphia, Saunders, 2006.
Massaging the finger close to the puncture site can also help increase blood flow.

19. Dermal Puncture Procedure
4. Hold the finger firmly to prevent moving during the puncture. 5. Make the puncture. Count to two before lifting the blade to make sure that the blade has made a complete puncture and retracted. Dispose of lancet in sharps container.
If you fail to get enough blood, you must begin the procedure again with a new lancet and a new microcollection container. After two unsuccessful attempts, call for help from another phlebotomist.
Courtesy of Zack Bent.  From Garrels M, Oatis CS: Laboratory Testing for Ambulatory Settings: A Guide for Health Care Professionals.  Philadelphia, Saunders, 2006.

20. Dermal Puncture Procedure
6. Prepare to collect the sample. - Wipe away the first drop with a clean gauze to prevent tissue fluid contamination of the specimen. - Keep the finger in a downward motion applying a “squeeze and release” pressure to the finger.
Constant massaging will cut off blood flow and not allow the capillaries to refill. It will also cause hemolysis and introduce tissue fluid into the specimen.

21. Dermal Puncture Procedure
7. Collect the sample. - Touch the scoop of the tube to the drop, allowing it to run into the tube. Make sure to mix the number of times required by the manufacturer. - Hold capillary tubes horizontally without touching the skin so as to prevent tissue fluid contamination.
Do not scrape the skin with any kind of collection container. This causes hemolysis, activates platelets and contaminates the sample with epithelial cells.

22. Dermal Puncture Procedure
Point out the difference in holding technique when using a microcollection tube and a capillary tube.
Courtesy of Zack Bent.  From Garrels M, Oatis CS: Laboratory Testing for Ambulatory Settings: A Guide for Health Care Professionals.  Philadelphia, Saunders, 2006.

23. Dermal Puncture Procedure
- Order of collect for dermal puncture: * Slides first to minimize the effects of platelet clumping. * Lavender tubes for CBCs. * Other tubes with anticoagulants. * Serum tubes last.

24. Dermal Puncture Procedure
8. Complete the procedure. - Apply a bandage after bleeding has stopped. Do not bandage children under 2 years of age since they could remove and choke on the bandage. - Make sure that equipment has been picked up and bed rails are up. - Label specimen, remove gloves and wash hands. - Thank the patient.
Make sure that no equipment or puncture devices are left in the childs crib.

25. Bleeding Time Test (BT)
A BT measures the length of time required for bleeding to stop after an incision is made.
A BT is a screening test to assess the integrity of the vascular system and platelet function.
Normal BT is 2 to 10 minutes.
Abnormal BT can be due to vascular disorders, platelet disorders, skin conditions, or medications that can interfere with clotting like aspirin, streptokinase or ethanol.

26. Abnormal BT Results
A BT of 15 to 20 min. can mean that the patient has a condition that is interfering with normal platelet plug formation or the test was performed incorrectly.
Repeat the test if only one incision was made; if two incisions were made and are within minutes of each other, it is not necessary to repeat the test.
Incision dept is set at 1mm deep and 5 mm wide. A double blade will make two incisions and is like doing the test in duplicate.

27. Bleeding Time (BT) Procedure
1. Assemble your equipment: - Alcohol pads - Blood pressure cuff - BT device - Stopwatch - Filter paper - Bandages
Have equipment to show the students.

28. Bleeding Time (BT) Procedure
2. Prepare the patient. - Tell the patient that scarring may occur. - Ask about any aspirin or product containing salicylates, taken within the last 7 to 10 days, or Ibuprofen within 24 hrs. that could inhibit platelet function.

29. Bleeding Time (BT) Procedure
3. Position the arm, select, and clean the site. - Select a site 5 cm. below the antecubital crease free of veins, scars, hair, and bruises. - Clean with alcohol and allow to dry.

30. Bleeding Time (BT) Procedure
4. Apply the blood pressure cuff. - Inflate cuff to 40 mm Hg. - Maintain the pressure throughout procedure. - Wait 30 to 60 sec. after inflation to make puncture. 5. Position the device parallel to the crease of the arm and 5 cm. below.
Placing the device perpendicular to the crease of the arm will reduce scarring but the results are not as accurate.

31. Bleeding Time (BT) Procedure
6. Make the incision and start timing. - Use firm pressure on the skin. - Activate device and start the stopwatch at the same time. - Remove device after the blade retracts. 7. Wick the blood every 30 seconds. - Touch only the edge of the drop until the drop disappears and you can see the site.
Touching the skin will disturb the platelet plug being formed and falsely prolong test results.

32. Bleeding Time (BT) Procedure
Note the BP cuff set to 40 mm Hg, the stopwatch and the filter paper just touching the drop.

33. Bleeding Time (BT) Procedure
8. Complete the test. - Bleeding has stopped when blood is no longer absorbed by the filter paper. - Record the time and remove cuff. 9. Attend to the patient. - Clean the arm (do not use alcohol). - Apply a butterfly bandage and tell patient to keep on for 24 hrs.
Use of the butterfly bandage can help minimize scarring.

34. Ancillary Blood Glucose Testing
Performed at the patient’s bedside.
Used to monitor patients with diabetes mellitus.
Follow the procedure from the manufacturer of the instrument that you are using.
Always make sure to calibrate and run controls prior to testing the patient.
Know what to do with critical values.
Demonstrate use of a glucose meter to students, showing them how to calibrate and run controls. See if you have a student that is a diabetic who may want to demonstrate the use of his meter.