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The procedure that will have had done to you is known as an intravenous guanethidine block. 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 overactive 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’.
Local anaesthetic and guanethidine are injected into a vein in your painful limb, below a tourniquet to concentrate the drug on the affected nerves. After releasing the tourniquet your limb will go bright pink as the circulation returns. Some of the drug which has not been absorbed will go into the general blood stream and probably make you feel a bit dizzy – especially after the first one or two treatments. This usually wears off quite quickly but some people feel muzzy and tired for a couple of days until they get used to the drug. The pain relief is not immediate – it can take several of these treatments for improvement to be seen, and in fact the pain may seem temporarily worse after the first treatment – so do not let this discourage you. This therapy will be evaluated after each session so that it will only be continued if there is a positive effect.
The pain relief should allow you to gradually increase your activities. It is important that you try to use the limb normally as soon as you can. This will be helped by the pain relief as it develops. Exercise improves the function of muscles, joints and bones.
AFTER THE TREATMENT YOU MUST NOT DRIVE A MOTOR VEHICLE FOR THE REMAINDER OF THE DAY
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