Multidisciplinary Pain Clinic

Sympathetic Nerve Blocks

Sympathetic Nerve blocks are used for treating disorders of the sympathetic nervous system.


  • Q: Are there alternatives to sympathetic blocks?

    A: In most cases sympathetic blocks are being offered for Complex Regional Pain Syndrome (CRPS). The primary treatment for CRPS is exercise and mobilization. There are a variety of medications that may be effective for CRPS and other neuropathic pain and you should discuss this with your physician.

  • Q: Can the sympathetic nerves be permanently destroyed?

    A: This is an option that has been offered to patients in the past. Recent evidence suggests the pain relief obtained by permanent sympathectomy is often ineffective or temporary and the pain and other side effects may actually be worse. This is something you should discuss with your doctor.

  • Q: How are sympathetic blocks done?

    A: There are two different ways that sympathetic blocks can be performed:

    1. Intravenous regional blocks can be done on your arm or on your leg. A small intravenous needle will be inserted in your hand or in your foot. A tourniquet will be applied to your upper arm or to your thigh. The tourniquet will be inflated so that no blood can enter or leave your arm or leg. After that some medications will be injected. These medications include guanethidine a drug which blocks your sympathetic nervous system and lidocaine a local anesthetic. Occasionally a steroid, ketorolac an anti-inflammatory or magnesium may be added. The tourniquet will be left up for 20 minutes. After 20 minutes the tourniquet will be deflated. When this happens some of the medication will go to the rest of your body. This may make you feel light headed. A stellate ganglion block can be done for the arm and a lumbar sympathetic block can be done for the leg.
    2. The stellate ganglion is a bundle of nerves in the neck. A needle is inserted adjacent to your windpipe, below and to the side of your voice box. Some local anesthetic (freezing) will be injected. This will block the sympathetic nervous system on the same side. You will notice that your eyelid may droop. You may also experience a stuffy nose. You may get a headache. You may have some hoarseness or trouble swallowing that will be temporary. In rare cases if the local anasthetic is injected into one of the blood vessels in the neck you may have a seizure. This is a very rare event and we are prepared to treat it in the pain clinic. A lumbar sympathetic block can be done for pain in your legs. The lumbar sympathetic ganglion is located in front and to the side of your spine. In order to freeze this ganglion, it is necessary to pass a needle adjacent to your spinal column. This requires X-ray control to accurately locate the ganglion and it may be necessary to make you a little sleepy. Because of this, this type of injection needs to be booked in advance and cannot be offered on short notice. In general intravenous regional blocks are satisfactory for the foot.
  • Q: How long do these blocks last?

    A: The duration of local anesthetic is about 6 hours although sympathetic nerves are more sensitive to local anesthetic. Guanethidine lasts for about 3 days. In some cases for reasons that are poorly understood, the pain relief may last much longer than this.

  • Q: How many blocks will I need?

    A: This will depend on your condition and your response to the blocks. If you do not respond to the first block, it may be worthwhile doing a second or third block.

  • Q: What is the the sympathetic nervous system?

    A: You have heard of an adrenaline rush. Adrenaline (epinephrine) and noradrenaline (norepinephrine) are chemicals produced by the body that regulate the heart rate, blood pressure and other functions.

  • Q: What should I do after the block?

    A: You should inquire before the block, whether it is okay to drive home afterwards. With lumbar sympathetic blocks, you can never drive home afterwards. Generally when you have your first stellate or intravenous regional block, you should make arrangements to be driven home afterwards. If you are being treated for complex regional pain syndrome or reflex sympathetic dystrophy, the main purpose of the block is to enable you to have physiotherapy. You should resume your physiotherapy the same day or the next day.

  • Q: Why am I being offered a sympathetic block?

    A: In response to an injury, the pain receptors in areas of your body may develop sympathetic receptors. In this situation the epinephrine or norepinephrine released by your body may stimulate the pain receptors causing pain. One such condition is reflex sympathetic dystrophy or as it is now known, Complex Regional Pain Syndrome (CRPS). Sympathetic blocks may reduce the pain that you have enabling you to get physiotherapy and exercise. Occasionally because of problems with your circulation, you may be offered a sympathetic block.