An intravenous guanethidine (IVG) block is an injection into a limb that is painful due to the activity of the sympathetic nerves.
By injecting a local anaesthetic and guanethidine into the affected limb the sympathetic nerves can be blocked.
It is usually given as a weekly course of injections, the effects gradually building up each time until the pain is controlled. It is important not to miss a treatment so that this accumulating effect is not lost.
Guanethidine is a drug which works against the sympathetic nerves, part of the nervous system which normally controls the automatic functions in the body including constriction/dilation of the blood vessels, and sweating. We sometimes need to damp down the effects of these nerves when they become over-active following an operation or injury. They may then interfere with the normal function of the nerves carrying pain and sensation, resulting in unpleasant and abnormal feelings like tingling, burning, and hypersensitivity of the skin. This condition, which can seriously hinder healing of the condition, is sometimes referred to as reflex sympathetic dystrophy or Chronic Regional Pain Syndrome.