Phlebotomy Procedures and Order of Draw Flashcards

What is the primary purpose of the sodium citrate additive in light blue-top tubes?

Answer: To chelate calcium and prevent clotting, preserving the blood in a liquid state for coagulation testing (PT, PTT, INR, fibrinogen)

Sodium citrate is a calcium-chelating anticoagulant — calcium is a required cofactor in the coagulation cascade; chelating it prevents clotting and preserves clotting factor activity for accurate PT/PTT/INR testing.

Which of the following veins is LEAST preferred for routine venipuncture and why?

Answer: The basilic vein, because it lies near the brachial artery and median nerve, increasing the risk of neurovascular injury

The basilic vein runs along the medial (pinky) side of the arm and is in close proximity to the brachial artery and median nerve; accidental arterial puncture or nerve damage is a greater risk with basilic vein access than with the median cubital or cephalic veins.

What is the recommended needle gauge for routine adult venipuncture?

Answer: 21–23 gauge (21G for most adults, 23G for small or fragile veins)

21–23 gauge needles are standard for adult venipuncture: 21G provides good flow for most adults, 23G is used for patients with small or fragile veins, while larger gauges (16–18G) are reserved for high-volume blood donations or rapid transfusion.

What does the term 'hematoma' refer to in the context of phlebotomy, and what is the primary preventive measure?

Answer: Accumulation of blood in the tissue surrounding the puncture site, causing bruising and swelling; prevented primarily by applying continuous pressure until bleeding completely stops

A hematoma forms when blood leaks out of the vein into surrounding tissues; the most effective prevention is maintaining continuous, firm, direct pressure on the site for 3–5 minutes after needle removal until hemostasis is complete.

What special consideration must a medical assistant make when drawing blood from a patient with a peripheral IV line in the antecubital fossa?

Answer: Draw from the opposite arm or a site distal to the IV insertion point in the same arm (not from the same vein above the IV); IV fluids dilute blood and alter analyte concentrations

Drawing blood from the same extremity as a running IV infusion contaminate the specimen with IV fluid, falsely diluting analytes and altering results — always use the opposite arm, and if unavoidable, draw below the IV site after the IV has been off for at least 2 minutes.

What is the correct action when a blood culture is ordered along with routine blood tests in the same draw session?

Answer: Collect blood culture bottles FIRST before any other tubes to minimize contamination of the sterile culture sample

Blood culture bottles are collected first in the order of draw because they require strict sterile technique — collecting them before other tubes prevents any potential additive carryover from earlier tubes and minimizes skin contamination introduced during the puncture.