سحب عينات الدم Venipuncture

من طرف **المسلمانى** الثلاثاء مارس 16, 2010 6:40 pm

Venipuncture

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.

Observe standard precautions (see Appendix A). If latex allergy is suspected, use latex-free supplies and equipment.
Position and tighten a tourniquet on the upper arm to produce venous distention (congestion). For elderly persons, a tourniquet is not always recommended because of possible rupture of capillaries. Large, distended, and highly visible veins increase the risk for hematoma.
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 to 2 mEq/L (mmol/L). Select an accessible vein.
Cleanse the puncture site, working in a circular motion from the center outward, and dry it properly with sterile gauze. Povidone-iodine must dry thoroughly.
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.
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.

P.60

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.
Remove the tourniquet before removing the needle from the puncture site or bruising will occur.
Remove needle. Apply pressure and sterile dressing strip to site.
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.
Take action to prevent these venipuncture errors:
- Pretest errors
  - Improper patient identification
  - Failure to check patient compliance with dietary restrictions
  - Failure to calm patient before blood collection
  - Use of wrong equipment and supplies
  - Inappropriate method of blood collection
- Procedure errors
  - Failure to dry site completely after cleansing with alcohol
  - Inserting needle with bevel side down
  - Using too small a needle, causing hemolysis of specimen
  - Venipuncture in unacceptable area (eg, above an intravenous [IV] line)
  - Prolonged tourniquet application
  - Wrong order of tube draw
  - Failure to mix blood immediately that is collected in additive-containing tubes
  - Pulling back on syringe plunger too forcefully
  - Failure to release tourniquet before needle withdrawal
- Posttest errors
  - Failure to apply pressure immediately to venipuncture site
  - Vigorous shaking of anticoagulated blood specimens
  - Forcing blood through a syringe needle into tube
  - Mislabeling of tubes
  - Failure to label specimens with infectious disease precautions as required
  - Failure to put date, time, and initials on requisition
  - Slow transport of specimens to laboratory

Note

A blood pressure cuff inflated to a point between systolic and diastolic pressure values can be used.

Note

The Vacutainer system consists of vacuum tubes (Vacutainer tubes), a tube holder, and a disposable multisample collecting needle.

Interventions

Pretest Patient Care