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Introduction ⬇

Venipuncture allows procurement of larger quantities of blood for testing. Care must be taken to avoid sample hemolysis or hemoconcentration and to prevent hematoma, vein damage, infection, and discomfort. Usually, the antecubital veins are the veins of choice because of ease of access. Blood values remain constant no matter which venipuncture site is selected, so long as it is venous and not arterial blood. Sometimes, the wrist area, forearm, or dorsum of the hand or foot must be used. Blood values remain consistent for all of these venipuncture sites.

  1. Observe standard precautions (see Appendix A). If latex allergy is known or suspected, use latex-free supplies and equipment.

  2. Assess the patient for fear or anxiety related to the procedure. Provide education, reassurance, and a supportive presence.

  3. Position and tighten a tourniquet on the upper arm to produce venous distention (congestion). For older persons, a tourniquet is not always recommended because of possible rupture of capillaries. Large, distended, and highly visible veins increase the risk for hematoma.

  4. Ask the patient to close the fist in the designated arm. Do not ask patient to pump the fist because this may increase plasma potassium levels by as much as 1–2 mEq/L (mmol/L). Select an accessible vein.

  5. Cleanse the puncture site, working in a circular motion from the center outward, and dry it properly with sterile gauze. Chlorhexidine must dry thoroughly.

  6. To anchor the vein, draw the skin taut over the vein and press the thumb below the puncture site. Hold the distal end of the vein during the puncture to decrease the possibility of rolling veins.

  7. Puncture the vein according to accepted technique. Usually, for an adult, anything smaller than a 21-gauge needle might make blood withdrawal more difficult. A Vacutainer system syringe or butterfly system may be used.

  8. Once the vein has been entered by the collecting needle, blood will fill the attached vacuum tubes automatically because of negative pressure within the collection tube.

  9. Remove the tourniquet before removing the needle from the puncture site or bruising will occur.

  10. Remove needle. Apply pressure and sterile dressing strip to puncture site.

  11. The preservative or anticoagulant added to the collection tube depends on the test ordered. In general, most hematology tests use EDTA anticoagulant. Even slightly clotted blood invalidates the test, and the sample must be redrawn.

  12. Take action to prevent these venipuncture errors:

    1. Pretest errors

      1. Improper patient identification

      2. Failure to check patient compliance with dietary restrictions

      3. Failure to calm patient before blood collection

      4. Use of wrong equipment and supplies

      5. Inappropriate method of blood collection

    2. Procedure errors

      1. Failure to dry site completely after cleansing with alcohol or chlorhexidine

      2. Inserting needle with bevel side down

      3. Using too small a needle, causing hemolysis of specimen

      4. Venipuncture in unacceptable area (e.g., above an intravenous [IV] line)

      5. Prolonged tourniquet application

      6. Wrong order of tube draw

      7. Failure to mix blood immediately that is collected in additive-containing tubes

      8. Pulling back on syringe plunger too forcefully

      9. Failure to release tourniquet before needle withdrawal

    3. Posttest errors

      1. Failure to apply pressure immediately to venipuncture site

      2. Vigorous shaking of anticoagulated blood specimens

      3. Forcing blood through a syringe needle into tube

      4. Mislabeling of tubes

      5. Failure to label specimens with infectious disease precautions as required

      6. Failure to put date, time, and initials on requisition

      7. Slow or delayed transport of specimens to the laboratory

Interventions ⬆

Pretest Patient Care

  1. Instruct patient regarding sampling procedure. Assess for circulation or bleeding problems and allergy to latex. Verify with the patient any fasting requirements. Diagnostic blood tests may require certain dietary restrictions of fasting for 8–12 hours before test. Drugs taken by the patient should be documented because they may affect results.

  2. Warn the patient that mild discomfort may be felt when the needle is inserted.

  3. Place the arm in a fully extended position with palmar surface facing upward (for antecubital access).

  4. If withdrawal of the sample is difficult, warm the extremity with warm towels or blankets. Allow the extremity to remain in a dependent position for several minutes before venipuncture. For young children, warming the draw site should be routine to distend small veins.

  5. Be alert to provide assistance should the patient become lightheaded or faint.

  6. Prescribed local anesthetic creams may be applied to the area before venipuncture; wait 60 seconds for light-skinned persons and 120 seconds for dark-skinned persons after application of the cream before performing the procedure.

Posttest Patient Care

  1. If oozing or bleeding from the puncture site continues for more than a few minutes, elevate the area and apply a pressure dressing. Observe the patient closely. Check for anticoagulant or ASA-type ingestion. If venous bleeding is excessive and persists for longer than 10 minutes, notify the healthcare provider.

  2. Be aware that the patient occasionally becomes dizzy, faint, or nauseated during the venipuncture. The phlebotomist must be constantly aware of the patient’s condition. If a patient feels faint, immediately remove the tourniquet and terminate the procedure. Place the patient in a supine position and elevate the legs, if possible. If the patient is sitting, lower the head between the legs and instruct the patient to breathe deeply. A cool, wet towel may be applied to the forehead and back of the neck, and, if necessary, ammonia inhalant may be applied briefly. Watch for signs of shock, such as increased heart rate and decreased blood pressure. If the patient becomes unconscious, notify the healthcare provider immediately.

  3. Prevent hematomas by using proper technique (do not allow the needle to pass through the vein), releasing the tourniquet before the needle is withdrawn, applying sufficient pressure over the puncture site, and maintaining an extended extremity until bleeding stops. If a hematoma develops, apply an ice pack.

  4. Assess the puncture site for signs and symptoms of infection, subcutaneous redness, pain, swelling, and tenderness.

  5. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

  1. In patients with leukemia, agranulocytosis, or lowered resistance, finger stick and earlobe punctures are more likely to cause infection and bleeding than venipunctures. Should a capillary sample be necessary, the cleansing agent should remain in contact with the skin for at least 5–10 minutes. Chlorhexidine is a topical antimicrobial. It should be allowed to dry completely. It may then be wiped off with alcohol and the site dried with sterile gauze before puncture.

  2. Do not draw blood from the same extremity being used for IV medications, fluids, or transfusions. If no other site is available, make sure the venipuncture site is below the IV site. Avoid areas that are edematous, are paralyzed, are on the same side as a mastectomy, are used for dialysis, or have infections or skin conditions present. Venipuncture may cause infection or circulatory impairment or impaired healing.

  3. Prolonged tourniquet application causes stasis and hemoconcentration and will alter test results. If a vein cannot be found within a minute, release the tourniquet temporarily to avoid tissue necrosis.

  4. Strenuous activity immediately before a blood sample draw can alter results because body fluids shift from the vascular bed to the tissue spaces and produce circulatory blood hemoconcentration. It may take 20–30 minutes of rest and reduced stress to reestablish fluid equilibrium.

  5. Assess for interfering factors, including cellulitis, phlebitis, venous obstruction, lymphangitis, or arteriovenous fistulas or shunts.

  6. To avoid spurious test results due to infusion of solutions, do not draw above an IV infusion. Choose a site distal to the IV line site.

  7. After two unsuccessful attempts, another trained member of the healthcare team should be called.

  8. Blood samples may be drawn off central lines. The lines must be flushed with saline before the blood draw and then 10 mL of blood drawn and wasted before obtaining blood for testing.