IV Therapy | Part Three – Vein Structures, IV Sites and Cannulation

Structure of Veins: Three Layers:

  1. Tunica Intima – endothelial lining, flat cells to let blood flow. Valves in this layer
  2. Tunica Media – muscular and elastic tissue, vasoconstrictor/dilators and nerve fibers in this layer
  3. Tunica Externa – connective tissue surrounding and supporting the vessel

IV Site Locations: never try distal to a failed spot, you may have blown the vein above it

  • Digital veins: use when other sites aren’t available
  • Metacarpal: between the knuckles
  • Cephalic: very common IV site
  • Median antebrachial: last resort
  • Basilic: ulnar border of hand and forearm
  • Antecubital: probably the most common IV site
  • Great saphenous: internal malleolus, inner thigh
  • Dorsal venous network: infants and toddlers
  • External Jugular: may be more important to manage the airway Veins of leg: use as last resort, thrombus formation

Performing IV Cannulation: Things to remember, other notes:

  • Explain the procedure to the patient
  • Check the IV fluid to be used
  • Prepare the Administration Set and the IV bag
    • 14-16 gauge for trauma, volume replacement, cardiac arrest
    • 18-20 gauge for medical conditions
  • Never leave a tourniquet in place for more than 2 minutes
  • Avoid areas of veins where valves are located
  • Stabilize the vein by anchoring it with the thumb and stretching the skin downward
  • Bevel of needle should be facing up when entering skin
  • Never insert the needle/catheter in so that less than half the catheter is outside the skin
  • Hold the needle stable and use the other hand to slide the catheter off the needle into the vein
  • Press with middle finger over the skin where the catheter is sitting
  • Remove needle carefully, leave catheter in place
  • Needle goes immediately into the sharps container
  • Connect IV tubing to the catheter hub
  • Hang bag 30-36 inches above insertion site
  • Open control valve briefly to check line patency
  • Cover IV site with ointment, place a sterile dressing on, tape catheter in place
  • Adjust flow rate for patient’s condition
  • Continue checking drip rate, IV site and patient vital signs periodically, especially for
  • Critical patients, pediatric/geriatric patients, those whose condition can be worsened by fluid overload, giving a type of fluid/drug that can cause tissue damage


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