Intravenous Guanethidine Blocks – Patient Information

2nd June 2007 at 15:42 BST by Dr C.A.Jenner MB BS, FRCA. Permalink.

This article discusses the usage of Intravenous Guanethidine Blocks for pain management.

Intravenous Guanethidine Blocks – Patient Information

What is Guanethidine?

Guanethidine is a pain management drug, having a specific effect on the sympathetic nerves and is generally used to control blood pressure.

Today, guanethidine is being successfully used as a drug for relief from chronic pain, with very few risk factors involved.

Intravenous Guanethidine Blocks

An intravenous guanethidine Block is a medical procedure carried out to treat painful conditions, which are confined to one of the limbs. It is a method of temporarily blocking the nerves, especially the sympathetic nerves to the affected limb.

The sympathetic nerves are the nerves, which control automatic functions of the body. They particularly control the constriction of blood vessels, which we can see when we get cold. These nerves are often involved in painful conditions affecting the limb.

Specific disorders in this category include Complex Regional Pain Syndromes (CRPS), like Sudek's atrophy, algodystrophy and reflex sympathetic dystrophy (RSD).

Usage and Application

The intravenous guanethidine blocks are normally used in patients with the following indications:

1. Acute Pain - It is very commonly used during surgery to assist with pain relief afterwards.
2. Chronic Pain – It is useful for any condition that causes chronic severe upper abdominal visceral pain, such as chronic pancreatitis.
3. Cancer Pain – It is also useful for upper abdominal organ cancer pain and is frequently used for carcinoma of the pancreas.

Commonly used mixtures include:

• Arm: Guanethidine 20 mg + 25 ml 0.5% lidocaine/prilocaine
• Leg: Guanethidine 30 mg + 30 ml 0.5% lidocaine /prilocaine

The Procedure

Once the patient has been adequately briefed about the procedure and possible complications, the actual process will start. It is important that the patient be fasted for at least 4 hours prior to the intravenous guanethidine block is administered. It should also be ensured that there is suitable resuscitation equipment in the area.

Here we list the main steps of the process:

1. The patient is admitted into one of the wards and a drip is inserted in the hand or foot of the affected limb.

2. Another drip is inserted into the back of the other hand and some monitors might also be attached.

3. A tourniquet is wrapped around the upper arm or thigh of the affected limb, which is elevated for a few minutes to empty the veins.

4. In some cases, it might also be required to gently squeeze out the excessive blood out of the affected limb, using an exsanquinator.

5. The tourniquet is then blown up to a high pressure, to about 100mhHg higher than the patient's systolic blood pressure.

6. The limb is now ready for the intravenous block. A mixture of guanethidine and local anaesthetic is injected thought the drip needle. This will lead to numbness and possibly some white blotches as well, which are short-lived.

7. You will then be required to rest for 20 minutes as the drug spreads to the tissues of the arm or the leg.

8. Finally, the tourniquet will be let down, making the arm feel warm and tingly.

9. The physician might keep you under observation for around 30 minutes, after which you will be allowed to go home.

Note: The intravenous Guanethidine blocks seldom work as a single treatment and participation of physiotherapist is called for. This is primarily to increase exercises for the limb after you've been administered the block.

Complications

The side-effects of the intravenous guanethidine blocks can either be significant and long-lasting or short-term, which generally do not last very long.

Here we briefly list the main amongst them.

A) Major effects

1. If the tourniquet deflates before 20 minutes, the entire mixture of the local anaesthetic and guanthendine can get into the systemic circulation. This can have serious consequences such as an extremely low blood pressure or even cardiac arrest.

2. If the injection pressure gets too high when the mixture is injected, some of the drug can escape into the systemic circulation through blood vessels that travel through the bone.

3. If the patient suffers from sever asthma, he/she can develop severe sneezing on tourniquet deflation.

B) Minor effects

The intravenous guanethidine blocks can cause allergic reactions such as an itchy rash on the affected limb. At times, this might require intravenous steroids and anti-histamines to be administered.

Appointments and more information

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