Patient Care · Pharmacology and contrast2 min read5-question check
Venipuncture and IV Safety
Higher gauge means a smaller needle. Watch the site during every injection and drop used sharps in the container at once.
Sites and gauges
Common venipuncture sites are the antecubital veins (median cubital, cephalic, and basilic), the forearm, and the back of the hand. Gauge numbers run backward: the higher the gauge, the smaller the needle. Most contrast injections use an 18 to 22 gauge catheter. Butterfly needles of 21 to 23 gauge suit small or fragile veins. Power injection at higher flow rates needs a larger catheter, often 18 or 20 gauge, ideally in the antecubital area.
Setup and flow
Apply a tourniquet a few inches above the site, clean the skin, and insert the needle bevel up at about 15 to 30 degrees. A flash of blood confirms entry. Release the tourniquet before injecting. For gravity flow, hang the bag about 18 to 24 inches above the vein. Raising the bag speeds flow, and lowering it slows flow. Clear air from the tubing before connecting. A large air volume can cause an air embolism. If one is suspected, turn the patient onto the left side with the head lowered and call for help.
The numbers
Infiltration means fluid has leaked into the tissue around the vein. Signs are swelling, pain, coolness, pale or tight skin, and slowed flow. Extravasation is the same event with a substance that can damage tissue, such as contrast. Worked example: an injector set for 100 mL at 4 mL/s should finish in 25 seconds. If the patient reports burning at 10 seconds, stop the injection at once. Remove the catheter, elevate the arm, apply a compress per policy, notify the radiologist, and document. Blistering, worsening pain, or numbness needs prompt evaluation.
Sharps safety
Put sharps into a puncture-resistant, labeled sharps container right away, at the point of use. Activate the safety device as soon as the needle is out. Never recap a used needle with two hands. Do not bend or break needles, and do not overfill the container; replace it when it is about three-quarters full. Bags, tubing, and gauze with visible blood go in biohazard waste. Follow facility policy for the rest.
Clinical Example
During a CT angiogram the patient says her arm feels tight and painful, and the site is swelling. The technologist stops the injector, removes the catheter, elevates the arm, and calls the radiologist. She records the estimated volume and site in the patient's chart.
Common Mistakes
- Thinking a 22 gauge needle is larger than an 18 gauge needle.
- Leaving the tourniquet on while injecting.
- Continuing an injection after the patient reports pain at the site.
- Recapping a needle with two hands or leaving it on the tray to discard later.
Why It Matters
The registry tests gauge sizes, infiltration signs, and safe sharps handling. Sharps and IV supply disposal is a named topic in the 2027 content specifications.
Key Relationships
- Higher gauge number → smaller needle diameter
- Raise IV bag → faster gravity flow
- Swelling, coolness, pain at site → stop and remove
- Suspected air embolism → left side, head down