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The most common type of cannula insertion in a healthcare environment involves the catheterization of a vein for easy administration of blood testing, saline solutions and medication. This procedure begins by a medical professional identifying a suitable vein and then sterilizing the site. A needle is then inserted at a 45-degree angle into the vein until blood appears in a flashback chamber, at which point the catheter can be slid forward into the vein and the needle can be removed all together.
According to the Queens University School of Medicine, most types of cannula insertion are performed as far from the heart as possible. The choicest location is the vein-laced top of the hand, followed by the forearm and then the crook of the arm. This way, if a vein becomes infected or the insertion is unsuccessful and the vein becomes deflated, other sites can be chosen to further up the extremities.
In more serious cases, patients may have to undergo a different kind of cannula insertion called a central IV. This involves inserting the catheter into larger veins such as the femoral artery at the pelvis, the vena cava in the chest, or the jugular vein in the neck. These are performed for a variety of reasons. More intensive medication can be administered with a central IV, and blood pressure can be monitored in real time. Other times, patients are obese or otherwise lacking in visible peripheral veins.
The basic procedure for a cannula insertion, which should only be practiced in an academic environment, starts by tying off a rubber tourniquet above the desired IV site and choosing a suitable vein. This site is cleaned with iodine or alcohol, then the skin below the site is lightly pulled as the needle is inserted, bevel pointing upward, into the vein at a 45-degree angle. When the flashback chamber shows blood the cannula assembly is lowered to almost level with the skin, and the needle is inserted just a millimeter more before the catheter surrounding the needle is pushed gently into the vein, which allows the needle to be retracted all together. While pressing on the vein above the cannula insertion, the blood flow stops until the catheter can be capped or connected with a source of saline solution. Taping down the catheter is the final step in the process.
Cannulas are used in other ways besides venal intrusion. An oxygen cannula fits onto the nostrils for an unobtrusive administration of supplemental oxygen. Different styles of cannulas also are used for procedures like liposuction, certain types of heart surgeries, and bladder relief for bed-ridden patients.