Venipuncture — “veni”, Latin for vein and “puncture”, meaning to penetrate, is the process of drawing blood from a vein. It’s the simplest way to collect cells and plasma for chemical study. Also known as phlebotomy, medical assistants perform venipuncture in most doctor’s offices when lab work is ordered as a value-added service for patients.
Why Does a Medical Assistant Draw Blood?
A medical assistant draws blood only under a physician’s order. Samples are used to diagnose and treat disease, type and crossmatch for transfusions, and monitor therapeutic drug levels.
Diagnose and Treat Disease
Changes in body chemistry can reflect illness. Blood tests detect conditions, such as:
- Autoimmune conditions
- Clotting abnormalities
- Heart, kidney and liver disease
- Nutritional deficiencies
Type and Crossmatch for Transfusions
The purpose of a “type and crossmatch” is to ensure blood is compatible for transfusions. It has three components, ABO-Rh typing, crossmatching and antibody screening. Typing categorizes blood by group — A, B, AB, O — and by Rh factor — positive or negative, while crossmatching checks a mix of donor and recipient blood for compatibility. Antibody screening looks for additional antibodies that could cause dangerous reactions. In a doctor’s office, a medical assistant may collect blood samples for preliminary typing and crossmatching before planned surgical procedures or in-office transfusions.
Monitor Therapeutic Drug Levels
Certain drugs, such as anticoagulants, anticonvulsants and some antibiotics, have a narrow therapeutic window, too little isn’t beneficial while too much can be toxic. Checking blood samples periodically ensures that prescribed medications are safe and having the desired effect.
The Venipuncture Process
Venipuncture requires both technical and people skills. Sound clinical judgment is a must. The process is designed to reduce errors, improve patient comfort and obtain the most accurate results. There are a few steps in the venipuncture process, they include:
Step #1: Check the Test Requisition
Identify the tests to be performed and verify that patients are properly prepared. Some analyses require fasting or taking medication before the draw.
Step #2: Explain the Process
Patients have the right to know the purpose of testing and what to expect. Proceed only with full consent.
Step #3: Position the Patient
A sturdy chair with armrests is ideal, but a patient with a history of fainting during venipuncture should lie down for safety. Fear and anxiety are best addressed before the procedure.
Step #4: Gather Needed Equipment
Tools for venipuncture include gloves, rubbing alcohol, needles, tourniquets, sample collection tubes, gauze, tape and bandages.
Gloves – all blood products could potentially be contaminated. Medical assistants should protect themselves with gloves.
Rubbing Alcohol – used to disinfect the area where the venipuncture will be performed. Combined with a brisk scrubbing motion, rubbing alcohol doesn’t sterilize skin, but it removes dirt and most bacteria.
Needles – come in a range of lengths and diameters for different veins. Diameter is noted in gauge from 18 for adults to 27 for children. The lower the number, the larger the diameter.
Lengths range from 0.5 to 1.5 inches. Short needles are usually best for superficial vessels, such as those on top of the hand. Longer needles help draw blood from the medial cubital vein at the bend of the elbow.
The medical assistant chooses the diameter and length based on the size of the patient, the location of the vein and the angle of approach.
Tourniquets – confines blood to the area from which it will be drawn. It keeps the vein plump and gives it a firm texture through which to insert the needle.
Sample Collection Tubes – venipuncture was once done with a needle and syringe, but new color-coded tubes with required additives already inside have simplified the process. Rubber-covered needles are screwed into plastic holders, and once inserted in the vein, the medical assistant presses the tubes onto the back of the needle. The pull of the vacuum allows blood to flow on its own.
Gauze, Tape and Bandages – when venipuncture is complete, the site is compressed with a layer of gauze to stop bleeding, and the medical assistant applies an adhesive bandage to protect the patient’s clothing. If the patient has sensitive skin or is allergic to bandage adhesive, secure the gauze with light, hypoallergenic paper tape instead.
Step #5: Assess Veins
Veins may be challenging to draw from if they’re too small, irregularly shaped or deep. Finding the best vessel improves the odds of success on the first draw attempt.
Step #6: Wash Hands
Gloves protect a medical assistant from contaminated blood but washing hands with soap and water protects the patient from infection.
Step #7: Disinfect the Site
Scrub the venipuncture site with an alcohol pad or alcohol-soaked cotton ball. Select tests require using alternative agents, such as chlorhexidine.
Step #8: Apply the Tourniquet
Medical assistants should apply tourniquets tight enough to constrict blood flow but not so tight as to cause pain. It can take several minutes to complete a draw, so ask the patient for feedback.
Step #9: Anchor the Vein
With the patient’s arm secure on an armrest, a vein can be anchored by placing a thumb just below the site. It provides stability and makes the vessel less likely to roll.
Step #10: Puncture the Vein
Insert the needle into the vein with a quick jab at a 30-degree angle. Press a tube into place and fill, each has a minimum fill line. Remove and replace tubes as needed until all samples are drawn.
Step #11: Wrapping Up
To avoid blood spurt, loosen the tourniquet before removing the needle. Cover the site with gauze as the needle is withdrawn, and when the bleeding stops, apply tape or a bandage.
Discard the used needle into a sharps container and carefully label tubes per workplace policy, mislabeled samples are usually rejected. Before patients leave, let them know when results can be expected and how to receive them.
Venipuncture isn’t a job requirement in all doctor’s offices. But as practices offer more on-site services for patient convenience, it’s a valuable skill that breeds opportunity. With experience, medical assistants can seek phlebotomy certification and open the door for future opportunities. It’s a great way to become indispensable to an employer and grow a rewarding career.
Interested in working with colleagues that want to help their patients stay healthy? Ready for an exciting new career in the medical assisting field? PCI Health Training Center’s Medical Assistant program prepares a graduate to work as an entry-level Medical Assistant. Within this general career category there are several specialty areas, including Medical Administrative Office Assistant, Clinic Assistant, Clinic Tech, Medical Office Manager, Phlebotomist and Physical Therapy Aide in a doctor’s office, clinic or hospital out-patient clinic. Contact PCI Health Training Center for more information on how to become a medical assistant and start a rewarding career today.
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