Site Selection and the Veins You Will Use
Venipuncture for a routine blood draw uses one of three veins in the <strong>antecubital fossa</strong> (the inside of the elbow). The <strong>median cubital</strong> is the first choice: it is the most stable, the least painful, and the least likely to roll or to sit over an artery. The <strong>cephalic</strong> runs along the thumb side of the arm and is the second choice. The <strong>basilic</strong> runs along the pinky side and is the least preferred because it sits closer to the brachial artery and the median nerve; if it is the only viable option, the CCMA uses extra caution to avoid nerve injury. Hand veins are acceptable for difficult draws but are more painful and more prone to bruising. The <strong>dorsal venous network</strong> on the back of the hand is the last resort; the skin is thinner, the veins are smaller, and the patient feels it more. Never draw from a site that is scarred, tattooed, edematous, infected, on the same side as a mastectomy, or on the same side as an IV infusion.
The CLSI Order of Draw
When a venipuncture uses multiple tubes, the order in which the tubes are filled is the <strong>CLSI order of draw</strong>, and following it prevents cross-contamination of additives between tubes. The order is: <strong>blood culture bottles first</strong> (sterility is the priority), then <strong>light blue</strong> (sodium citrate for coagulation studies), then <strong>red</strong> (no additive, for serum tests), then <strong>serum separator tube (SST, gold or tiger-top)</strong>, then <strong>green</strong> (heparin), then <strong>lavender or pink</strong> (EDTA for hematology), then <strong>gray</strong> (sodium fluoride/potassium oxalate for glucose). Tubes are filled to the volume marked on the label; under-filling an anticoagulant tube changes the ratio and invalidates the result. Each tube is inverted gently the number of times specified by the manufacturer (typically 3 to 8 inversions); shaking hemolyzes the specimen and can cause the lab to reject it.
Complications, Rejections, and the Right Response
The most common venipuncture complication is <strong>hematoma</strong>, caused by blood leaking into the tissue around the puncture site. The CCMA prevents it by applying firm pressure for 3 to 5 minutes (longer if the patient is on anticoagulants), by not bending the arm, and by not massaging the site. <strong>Nerve injury</strong> happens when the needle tracks into a nerve; the patient reports a sharp, electric-shock pain that radiates down the arm, and the CCMA releases the tourniquet and removes the needle immediately. <strong>Hemolysis</strong> (breakage of red blood cells) is caused by using a needle that is too small, by pulling the syringe plunger too hard, by mixing the tube too vigorously, or by drawing from a site that is still cold. The lab rejects hemolyzed specimens, and the patient has to come back. <strong>Failed draw</strong> (no blood return) is most often a needle that has passed through the vein; the CCMA pulls back slightly, rotates the needle half a turn, or asks the patient to make a fist (then release it) before trying a new site. The CCMA documents every attempt, every complication, and every action taken.