Hematomas

Hematoma: A Frequent Exam Topic in Phlebotomy

A hematoma is a localized collection of blood outside the blood vessels, typically caused by a needle puncturing the wall of a vein during venipuncture and allowing blood to leak into the surrounding tissue. It is one of the most common complications of phlebotomy.^[1] For exam candidates and practicing phlebotomists, understanding how to prevent, recognize, and manage hematomas is critical for patient safety and test success.

Why this matters on exams: Hematoma questions appear frequently on the Phlebotomy Technician Certification Exam (e.g., ASCP, NHA) and are often linked to proper vein selection, needle angle, and post-puncture care.^[2]

Core Terminology for Hematoma Understanding

• Hematoma – A swelling caused by blood pooling under the skin due to a torn or punctured vessel. Unlike a contusion (bruise), a hematoma involves a palpable mass.
• Ecchymosis – A flat, purplish discoloration of the skin caused by blood seeping into the tissues; often develops after a hematoma resolves.
• Venipuncture – The process of puncturing a vein to obtain a blood sample.
• Needle gauge – The diameter of the needle; smaller numbers (e.g., 21G) indicate larger diameters, which can increase hematoma risk if the vein is small or fragile.^[1]
• Fragile veins – Veins that are easily damaged, often seen in elderly patients, those on anticoagulants, or patients with chronic illness.
• Hemostasis – The process of stopping bleeding; inadequate hemostasis after needle removal can lead to hematoma formation.

Formation and Causes of Hematoma

How a Hematoma Forms

1. The phlebotomist inserts the needle through the skin and into the vein.
2. If the needle goes completely through the posterior wall of the vein (through-and-through puncture), or if the needle slips partially out of the vein, blood escapes into the surrounding tissue.^[3]
3. The escaping blood accumulates under the skin, causing rapid swelling and discoloration.
4. If pressure is not applied promptly, the hematoma can enlarge, causing pain and potential damage to nearby nerves or arteries.

Common Causes of Hematoma Formation

• Improper needle angle – Too steep an angle (e.g., >30 degrees) increases the risk of a through-and-through puncture.^[1]
• Poor vein selection – Using veins that are too small, fragile, or rolling.
• Excessive probing – Moving the needle after insertion to locate the vein.
• Inadequate pressure after needle removal – Not holding pressure long enough (minimum 2–3 minutes for normal patients; longer for anticoagulated patients).^[4]
• Removing the tourniquet too late – Tourniquet should be released as soon as blood flow is established; leaving it on too long increases venous pressure and leak risk.
• Using an incorrect needle gauge – A large-gauge needle in a small vein can tear the vessel wall.

Clinical Indicators of Hematoma Formation

• Rapid swelling at the puncture site, often occurring within seconds.
• Pain or tenderness that may be sharp or burning.
• Discoloration – The area becomes red, then purplish-blue.
• Palpable mass – The swelling feels firm to the touch.
• Patient reports discomfort during or immediately after the draw.
• Loss of pulse or pallor in severe cases (if a large artery is involved – rare in routine phlebotomy).
• Delayed bruising – Ecchymosis may appear hours later as the hematoma resolves.^[5]

Detecting and Documenting Hematomas

• Visual inspection – Observe the puncture site for any signs of swelling during and immediately after the draw.
• Palpation – Gently feel the area; a hematoma will feel like a raised, tense lump.
• Patient feedback – Ask the patient if they feel any pain or burning during the venipuncture; sudden onset of pain may indicate a hematoma forming.
• Documentation – Record the occurrence, size, location, and any interventions taken. This is important for medical-legal purposes and continuity of care.^[2]

Immediate Response and Management Steps

• Immediately stop the blood draw – Remove the needle and tourniquet.
• Apply direct pressure – Use a sterile gauze pad and apply firm pressure to the site for a minimum of 2–3 minutes (longer if the patient is on anticoagulants). Do not bend the arm; keep the arm extended.^[4]
• Elevate the arm – If possible, raise the affected limb above heart level to reduce blood flow to the area.
• Apply a cold compress – Ice wrapped in a cloth can be applied for 10–15 minutes to reduce swelling and pain. Do not apply ice directly to the skin.
• Reassure the patient – Explain that the hematoma will gradually resolve over 1–2 weeks and that most resolve without further treatment.
• Choose another site – If a second draw is needed, select a different vein (preferably on the opposite arm).
• Document – Note the incident, the size of the hematoma (e.g., 2 cm diameter), and any patient education provided.

Preventive Measures and Potential Complications

Prevention Strategies

• Select an appropriate vein – Use a vein that is visible, palpable, and large enough for the needle gauge chosen. Avoid veins that are fragile, sclerotic, or near joints (e.g., antecubital fossa if the patient has poor skin integrity).^[1]
• Anchor the vein – Use the thumb to hold the skin taut below the puncture site to prevent the vein from rolling.
• Use the correct needle angle – Insert the needle at a 15–30 degree angle (depending on vein depth).^[3]
• Release the tourniquet promptly – As soon as blood begins to flow into the tube, release the tourniquet.
• Avoid excessive reinsertion – If you miss the vein, do not probe; remove the needle and start fresh at a new site.
• Apply adequate pressure after removal – Hold pressure for at least 2 minutes (5 minutes if the patient is on anticoagulants). Instruct the patient not to bend their arm or carry heavy items for the next 15–20 minutes.
• Use the smallest needle possible – For routine draws, a 21–23 gauge needle is typically appropriate. Use a smaller gauge (e.g., 23G) for small or fragile veins.

Potential Complications if Untreated

• Infection – A large hematoma can become an ideal medium for bacterial growth if the skin barrier is compromised.
• Nerve damage – A rapidly expanding hematoma in the antecubital fossa can compress adjacent nerves (e.g., median nerve), leading to paresthesia or motor weakness.^[5]
• Compartment syndrome – Rare but serious; occurs when blood accumulates in a tight fascial compartment, impairing circulation.
• Phlebitis – Inflammation of the vein wall may occur if the hematoma is near the puncture site.
• Prolonged discomfort and scarring – The area may remain tender for weeks.

Test-Ready Insights and Mnemonics

• Most common cause of hematoma during venipuncture? Through-and-through puncture (needle passing through the back wall of the vein).^[3]
• What is the first action when a hematoma begins to form? Remove the needle and apply direct pressure.
• How long should pressure be held? At least 2–3 minutes (longer for coagulopathic patients).
• What vein characteristic increases hematoma risk? Small, fragile, or rolling veins.
• When should a tourniquet be released? As soon as blood flows into the collection tube (do not wait until the end).
• What is the recommended needle angle for superficial veins? 15–20 degrees; for deeper veins, up to 30 degrees.
• Which patient populations are at higher risk? Elderly, patients on anticoagulants (warfarin, heparin, DOACs), those with liver disease, and patients with chronic steroid use.^[4]
• Memory aid for prevention: “VAPOR” – Vein selection, Angle, Pressure (tourniquet release), Only one attempt, Remove needle smoothly and apply pressure.
• On exam questions, if a patient reports sudden burning pain during a draw, immediately suspect a hematoma.
• Know that a hematoma can cause a false decrease in some lab values (e.g., hemolysis can affect potassium, LDH) if blood is drawn from the same arm below the hematoma.^[2]

References & Sources

1. Clinical and Laboratory Standards Institute (CLSI). Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture. CLSI document GP41-A7, 7th ed. Wayne, PA: CLSI; 2017. https://clsi.org/standards/products/general-laboratory/documents/gp41/
2. Hood, J. & Engel, E. Phlebotomy: Worktext and Procedures Manual. 4th ed. St. Louis, MO: Elsevier; 2019. https://www.elsevier.com/
3. McCulloch, J. M. & Miller, A. A. Phlebotomy Essentials. 7th ed. Burlington, MA: Jones & Bartlett Learning; 2020. https://samples.jblearning.com/9781284209945/9781284209501_FMxx_i_xxxiv_Secured.pdf
4. Occupational Safety and Health Administration (OSHA). Bloodborne Pathogens Standard (29 CFR 1910.1030). U.S. Department of Labor. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1030
5. Shim, J. S. & Kim, J. H. “Hematoma After Venipuncture: Prevention and Management.” Korean Journal of Clinical Laboratory Science. 2018;50(3):245–250. https://doi.org/10.15324/kjcls.2018.50.3.245