I’m not one of those people with a phobic reaction to having a cannula inserted into my arm (especially if it’s done by a professional, practised nurse, rather than some bleary, junior medic).
I’ve noticed that a lot of thinking has gone into the design of these things to make them easy to insert and keep them sealed against infective agents. The English NHS buys about 20M of these a year, so the cost implications of any change are significant.
One problem is that this design of cannula creates a finger-sized protruberance from the the surface of one’s skin…just asking to get snagged on a hospital gown, bedclothes, stethoscopes etc. After a few hours, any movement of the needle, driven by the external plastic collar, is painful and messy (forcing the needle into the vein wall).
Today’s invention is a fine nylon tube which is driven down the inside of the needle, after it has penetrated a blood vessel, by the attachment of a syringe or a tube leading to a ‘drip’. This proboscis greatly decreases the damage which the needle can do to the inside of a vein and the discomfort of wearing a cannula for a few days is therefore lessened.
In addition, when the needle is withdrawn, the nylon tube still protrudes from it, making it very unlikely that medical staff will prick themselves on a ‘sharp’ covered in someone’s blood.