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What is an IV cannula? What are the uses of an IV cannula?
An intravenous cannula allows doctors to administer medications with minimal discomfort to their patients.
Intravenous (IV) catheters (cannula) provide a pathway into the blood for fluid, blood products, or medication administration. It allows multiple blood samples to be drawn with minimal patient discomfort. They are mostly used to administer drugs and fluids; however, they can also be used to provide nutrition directly through the venous system. IV catheters can also help facilitate blood collection in animals with poor veins or who need multiple samples to be taken. Below are a few common tips to insert an IV cannula:
- Ask the patient to lie down, supine and horizontal. The blood will pool where the gravity takes it. If the patient is sitting upright or has their legs dangling, the blood will pool in dependent regions such as the veins of the legs rather than the veins of the hands.
- Apply a standard rubber tourniquet to the upper arm. Then, on top of this tourniquet, apply the blood pressure cuff from an automated blood pressure machine.
- Activate the blood pressure cuff in "Stat" mode or repeatedly inflate the cuff in "Manual" mode. The pneumatic blood pressure cuff is the best vein tourniquet and will be the most effective in making even the small veins grow prominent.
- Examine the arm carefully for the best vein. Do this by both inspecting and feeling the vein. Sometimes, the cord of the vein can be felt, even when it cannot be seen. Rather than sticking the patient's arm in multiple places, be patient and do not start until determining the best location.
- Stimulate the skin over this vein by tapping. This local stimulation makes the veins grow (releasing a regional vein-dilator or by blocking a regional vein-constrictor). This mechanism or technique works. Choose a standard IV catheter, either a 20-gauge or 22-gauge.
- Always anchor the skin over the vein by pulling distally with your nondominant thumb when you insert the IV catheter with your dominant hand. Anchoring and stretching the skin distally prevent the vein from rolling or moving during your insertion attempt.
- When you first hit the vein and blood begins to flow into the hub of your catheter, you may need to advance the device an additional 1-3 mm before you attempt to advance the catheter forward over the needle into the vein. Moreover, you must not move the nondominant thumb away so that the vein stays stationary.
- The IV catheter device is a catheter-over-a-needle device. When the needle tip first enters the vein, the catheter tip is not in the lumen of the vein yet. The 1-3 mm advance moves the tip of the plastic catheter into the vein.
- Once done, withdraw the inner needle and move the outer catheter further in the vein. Secure the cannula with sticky tapes.
- If unsuccessful in locating a vein in either arm, you can move to the foot and ankle region and start IV cannulation there.
Where is the best place to insert an IV cannula?
Places for IV insertion:
- The forearms are the perfect location for continuous fluids because they don't kink with arm bending. However, not everyone has great forearm options. Additionally, starting an IV line in the forearm vein does not always reliably give great blood return for blood work. However, this may mainly be considered in the emergency department (ED) where they typically draw blood work during IV insertions.
- Hand IVs are sometimes the easiest veins to see. However, they are usually relatively small veins and can usually only fit 20-22 g. They are great for short periods but can easily become irritated. Additionally, they limit the use of the hand and are more likely to start hurting the patient.
- The hands or upper arms have large veins close to the surface. Most facilities prefer to stick an IV in an arm, but there are exceptions. If the patient is extremely hard stick and needs access, you can look at the legs or lower extremities, but practice caution because there is a high risk of infection.
- If you cannot locate a vein in any extremity, consider the external jugular veins on the side of the patient's neck. With the patient positioned slightly head down, these veins are often prominent. The external jugular vein swells when the patient performs a Valsalva maneuver (hold your nose shut and blow your nose). A simple 1¼ inch, 20-gauge peripheral IV catheter will suffice. Because the size and diameter of the external jugular vein are larger than those of most arm veins and the external jugular vein is usually quite on the skin, cannulating this vein can be quite easy in skilled hands. Attach a 3-cc syringe onto the hub of the intravenous catheter device before attempting the insertion. Then, aspirate back with negative pressure. Once the catheter is inside the external jugular vein, the syringe will fill with blood, and you can advance the catheter into the vein.
