This is some information that I found on Google about Ganglion blocks.

There are many types of nerve blocks often used in the treatment of Reflex Sympathetic Dystrophy, but usually the initial block used is called ‘Stellate Ganglion Block’. The Ganglion nerves are situated in the upper neck and are part of the ‘Sympathetic Nervous System’, this system helps regulate the temperature sensation and blood flow in the body as well as regulating pain signals. By temporarily blocking these nerves, blood flow may be increased and pain signals may be diminished, it’s success may help diagnose whether the pain experienced is sympathetically maintained, but it is not conclusive, it is generally agreed that patients who are treated early in their illness respond better than those who have had the symptoms for a longer period (6 months+) patients who are in an advanced stage of the treatment may not respond at all.

The Ganglion block is a local anaesthetic such as ‘Lidocaine’, an ‘adrenaline’ drug may also be added to prolong the effect of the drug. The procedure takes only a few minutes, and involves inserting a needle into the nerve tissue situated at the side of the voice box. Usually a local anaesthetic is used to numb the area prior to the actual block, this is to make the procedure easier to tolerate. The patient should also be monitored for blood pressure and blood-oxygen supply.

Should the treatment prove successful the patient will probably be recommended for a course of further blocks, this may vary from 4 upwards, this varies from patient to patient. After the block, a patient will in all probability experience some nasal congestion on the side of the injection, they may also experience a lump in the throat, droopy eye and reddening of the eye along with headache, however these symptoms are generally short lived and most patients can resume normal activities the following day.

Hope it helps and good luck with the block tomorrow, please let us know how it goes.
Thanks