It's a fact of life that if you're admitted to hospital, you're probably going to have a needle stuck into you. And, of course, the mother of them all is the spinal needle. That's used to suck out the fluid that surrounds your central nervous system. Which has got to really hurt, right? Except that it doesn't, apparently.
At least not anywhere near as much as other injections, according to a study in this week's Lancet, which not only shows that spinals have an undeserved reputation, but also that so-called "routine" jabs hurt a lot more than doctors and patients might imagine. In the Italian study, 83% of patients thought a spinal injection would be most painful, while 80% said an intramuscular (IM) would hurt least. But after they had actually experienced them, nearly 90% said either IM or intravenous (IV) injections were most unpleasant, with only 11% rating the spinal as most painful.
If you push a sharp piece of metal through skin, it will hurt, but there are ways of reducing the pain. Probably the most common sort of injection is the IV, which often involves inserting a cannula (a short length of plastic tubing) into the vein to give drugs or fluids. Dr Bruno Simini, who carried out the Italian trial, says that patients should be anaesthetised before a cannula is inserted. He's right, but it doesn't always happen. You can apply anaesthetic cream which numbs the skin, but it takes about 20 to 30 minutes to work, and in an emergency there may not be time. It's usually reserved for children, although it can be used just as well on adults. The effect is never complete, and even if you prevent actual pain, the patient still feels the "pushing" sensation, which many children will interpret as pain.
The alternative is to inject a tiny blob of local anaesthetic just under the skin. Many doctors still argue that having a local injection is just as painful as the other injection, so why bother? But having had IV cannulae myself both with and without local, I can confirm that a tiny injection of local does not hurt anywhere near as much as having a 2mm diameter needle shoved into a vein.
The problem is that even a tiny amount of fluid under the skin can make its successful puncture afterwards more difficult. If you have to make two attempts instead of one, it rather defeats the object of the exercise. I always use local for anything other than the very smallest cannula, but some doctors are not comfortable with it.
Then there are IM injections. It's an easy way of giving drugs, but painful and unreliable. Simini states that "IM injections should belong in the past". Here, it is not the puncture of the skin that causes most pain, but the forcing of fluid into muscle fibres. The absorption from muscle into the bloodstream can be erratic, particularly in a shocked patient. On the whole, drugs are far better administered by the IV route, where their effects are immediate and predictable.
Generally speaking, doctors don't impale people just for the sake of it. But my advice is that if you're about to have a large drip put in and your physician says, "It'll only hurt a bit," ask if she's ever had one. Then ask for some local first.
• Dr Walker is an accident and emergency specialist in west Yorkshire.
