10 Questions
Why is a tourniquet used during the venipuncture procedure?
To make it easier to locate and access the vein
What is the purpose of venipuncture?
To collect blood from a vein for laboratory testing
Where is the antecubital vein typically located?
On the dorsum of the arm
What is used to cleanse the skin before performing venipuncture?
70% Isopropyl alcohol
What is the recommended angle for inserting the needle into the vein?
15° to 30°
Why is it important to push the plunger of the syringe to the top of the barrel before venipuncture?
To prevent air from being injected into the vein
How far should the needle be moved parallel to the vein after initial insertion?
1.5 cm
What should be done if blood does not immediately enter the syringe after puncturing the vein?
Withdraw the plunger slightly
How long should the dry gauze be pressed on the puncture site after withdrawing the needle?
1-2 minutes
Which of the following is NOT listed as a disadvantage of venous blood specimens?
The specimen may be contaminated by other fluids
Study Notes
Venipuncture Procedure
- Place forefinger on the hub of the needle and hold the syringe in the right hand, grasping the arm with the left hand and holding the skin taut with the thumb.
- Insert the needle at a 15° to 30° angle through the skin, lower the syringe, and move the needle parallel to the vein for about 1.5 cm, directing it into the vein.
Blood Collection
- Steady the syringe with the left hand and withdraw the required amount of blood by pulling the plunger back with the right hand.
- Release the tourniquet, let the patient open their fist, and place dry sterile gauze over the puncture site.
Post-Collection Procedure
- Withdraw the needle and expel the blood gently into a sterile tube.
- The operator should remain with the patient until the puncture site has stopped bleeding.
Precautions
- Clean the skin in a circular motion from center to periphery.
- Allow the alcohol to air dry for at least 30-80 seconds before proceeding.
- Do not touch the site after cleaning.
- Do not keep the tourniquet on for more than 1 minute.
- Remove the tourniquet before withdrawing the needle from the vein.
- Avoid collecting blood from sites of edema, mastectomy, hematoma, burn, scar, or fistula.
Advantages of Venous Blood Specimen
- Multiple and repeat examinations can be performed on one specimen.
- There are no variations in blood values if the specimen is obtained from different veins.
- Aliquots of plasma and serum can be frozen for future reference.
Disadvantages of Venous Blood Specimens
- Prolonged stasis produced by the tourniquet can render the specimen unsuitable for accurate hematologic tests.
- Some components are stable in anticoagulated blood, so platelet counts and sedimentation rate determinations should be performed within 2 hours after blood collection.
- Venipuncture can be a lengthy procedure and may be difficult to perform on children, obese patients, and patients in shock.
Requirements and Equipment
- Tourniquet, 70% isopropyl alcohol, sterile gauze, sterile cotton, sterile needle, sterile syringe, and sterile collecting vial are required.
Learn about the process of venipuncture, which involves collecting blood from a vein for laboratory testing. Understand the equipment required and the step-by-step procedure involved in this medical technique.
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