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  Treatment       Sympathetic Blocks      
 
 
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Indications

Sympathetic blocks are used in the pain relief clinic primarily for treating disorders of the sympathetic nervous system:-

  • CRPS I (Reflex Sympathetic Dystrophy, RSD)
  • CRPS II (Causalgia)
  • SMP (Sympathetically Maintained Pain)

They should not be used in isolation for these conditions, but they can be useful as part of a multi-disciplinary treatment program.

Other indications include:-
  • Visceral Pain Relief
    • Renal Colic, Acute and Chronic Pancreatitis, Upper Abdominal Visceral Cancer, and Cardiac Pain.
  • Improving Circulation
    • Peripheral Vascular Disease, Raynauds Disease, and to reverse the effects of accidental intra-arterial drug injection.
Guanethidine Biers Block

Mechanism Of Action

  • Guanethidine (sympathetic blocking drug) is rapidly taken up from the venous system by the peripheral nerves during the 20 minutes that a tourniquet is applied to the affected limb.
  • It has an immediate action locally on the peripheral sympathetic nerves. During the next 24 hours, the guanethidine is transported by the peripheral nerves to the dorsal root ganglion in the spinal cord, where it contributes further to the sympathetic block centrally.

Technique

  • The block should be performed in an area with suitable resuscitation equipment, and where there are trained assistants available.
  • The patient should be fasted for 4 hours before hand.
  • Two intravenous lines are inserted, one into the affected limb, and one in the back of a hand that is spare. The first line is used to inject the Guanethidine / Local Anaesthetic mixture, and the second line is there to act as emergency venous access should the need arise.
  • Vital signs monitoring is used throughout to measure heart rate, blood pressure and oxygen saturation.
  • Intravenous Sedation is used for patient comfort, and can be supplemented with Entonox (gas and air).
  • The upper part of the affected limb is wrapped in gauze (Velband) to protect it, and a tourniquet applied.
  • Excessive blood is gently squeezed out of the affected limb by using an exsanguinator .
  • The tourniquet is inflated to about 100 mmHg higher than the patient's systolic blood pressure and held at that pressure by a gas powered machine .
  • The Guanethidine mixture is injected slowly into the exsanguinated arm via the intravenous line , and the tourniquet is kept in place for 20 minutes.
  • Commonly used mixtures are as follows:-
    • Arm - Guanethidine 20 mg + 25 ml 0.5% lignocaine or 0.5% prilocaine
    • Leg - Guanethidine 30 mg + 30 ml 0.5% lignocaine or 0.5% prilocaine.
  • Whilst the tourniquet is inflated, the affected limb will go slowly numb from the combination of the local anaesthetic, and the lack of blood flow.
  • After 20 minutes the tourniquet is slowly deflated, allowing the blood to return to the affected limb. During this time all the guanethidine and local, anaesthetic has been absorbed by the peripheral nerves.

Complications

  • Major
    • Should the tourniquet deflate before 20 minutes, and before all the local anaesthetic and guanethidine has been absorbed, then significant amounts of both drugs can escape into the systemic circulation. Depending on the dose, this can cause a low blood pressure (guanethidine) or cardiac arrest (lignocaine).
    • Should the injection pressure rise too high when the mixture is initially injected, some of the drug can escape into the systemic circulation through blood vessels that travel through bone, and therefore not prevented by the tourniquet. It's important therefore not to inject too quickly or with too high a volume.
    • Unstable asthmatics can develop severe wheezing on tourniquet deflation due to the effects of traces of guanethidine leaking into the circulation and causing bronchoconstriction of the airways. This is usually managed with intravenous salbutamol and steroids.
  • Minor
    • Allergic reactions can occur to guanethidine causing an itchy rash in the affected limb, mostly settling spontaneously, but with some requiring treatment with intravenous steroids and anti-histamines.
Stellate Ganglion Block

Anatomy

  • The first thoracic (T1) sympathetic ganglion fuses with the inferior cervical ganglion to make the stellate ganglion , and sits at the top end of the sympathetic chain in front of the C7 vertebra of the neck.
  • The ganglion is a junction box, conveying sympathetic nerve messages from the T1 - T6 levels upwards to one half of the head and neck, and the arm on the same side.

Indications

Contraindications

  • Vocal cord palsy / recurrent laryngeal nerve palsy - the block should not be performed on the normal side for fear of causing airway obstruction at the level of the glottis.
  • Phrenic Nerve Palsy (diaphragm control) - the block should not be performed on the normal side or in those with significant chronic obstructive airways disease, for fear of causing respiratory embarrassment.
  • The block should not be done on both sides for obvious reasons.
  • All the other usual contraindications regarding bleeding and infection also apply.

Technique

  • The block is performed at the C6 level rather than C7, to reduce the complication rate. The anterior paratracheal approach of Leriche is the one that is most commonly performed.
  • All the usual precautions are taken about resuscitation equipment, fasting, intravenous cannulation, and monitoring as mentioned in the section above on Guanethidine Biers Block.
  • Intravenous Sedation is used for patient comfort.
  • The patient is positioned on their back (supine) with a small pillow under the shoulders to open up the neck area.
  • The local anaesthetic mixture is prepared before the injection. A 23 gauge 1" (blue) needle is attached via connecting tubing to a 10 ml syringe filled with a 50 / 50 mixture of 2% lignocaine and 0.5% chirocaine. All air bubbles are removed from the system prior to injection. The assistant operates the syringe plunger.
  • Chaissagnac's Tubercle is identified (tip of the transverse process of C6 opposite the cricoid cartilage), and the needle is inserted between trachea and the carotid artery until it sits on the transverse process of C6. To avoid arterial puncture the operator's fingers gently pull the carotid artery away from the midline. The needle tip is then lifted off the bone by 2 - 3 mm and held steady.
  • After a negative aspiration for blood and cerebrospinal fluid, the assistant injects 0.5 ml of the mixture. The patient is observed for any untoward reaction for a few seconds, and then another aspiration test is performed, followed by another 0.5 ml injection, and the patient observed again. This process is repeated until 5 ml has been injected uneventfully, following which the injection size can be increased to 1 ml bolus, until the whole 10 ml has been injected.
  • The patient is closely monitored every 5 minutes for the first 30 minutes.

Signs of a successful block include:-

  • Reddening of the conjunctiva in the eye
  • Meiosis (constriction of the pupil)
  • Ptosis (drooping eyelid)
  • Enophthalmos (eyeball sinking back into the eye socket a little)
  • One sided nasal stuffiness
  • A lump in the throat feeling
  • Hoarsening of the voice (recurrent laryngeal nerve block)
  • A warm pink arm / hand / face (one sided).
  • Rise in skin temperature of the affected arm (at least 2 deg C)
  • Relief of the sympathetic pain symptoms
  • All of these should resolve when the local anaesthetic wears off, except that the pain relief often lasts longer than expected.

Complications

  • Aspiration of food / liquids into the lungs - prevented by keeping the patient fasted until the recurrent laryngeal nerve block has worn off
  • Bleeding may cause a haematoma
  • T1 / T2 neuralgia can cause chest pain radiating down the inner arm.
  • Brachial plexus and phrenic nerve blocks (uncommon)
  • Pneumothorax (uncommon at the C6 level, more common at C7)
  • C6 transverse process osteomyelitis (should be minimised by sterile technique - more common after repeated blocks)
  • Vertebral artery injection causing seizures, loss of consciousness and cardiac arrest (rare)
  • Total spinal injection caused by injection into the cerebrospinal fluid (rare)
Coeliac Plexus Block

Anatomy

  • The coeliac plexus is also known as the solar plexus.
  • It is the main junction box for autonomic nerves supplying the upper abdominal organs (liver, gall bladder, spleen, stomach, pancreas, kidneys, small bowel, and 2/3 of the large bowel).
  • It receives it's sympathetic supply from:-
    • Greater Splanchnic Nerve (T5/6 to T9/10)
    • Lesser Splanchnic Nerve (T10/11)
    • Least Splanchnic Nerve (T11/12)
  • The upper abdominal organs receive their parasympathetic supply from the left and right vagal trunks which pass through the coeliac plexus but do not connect there.

Indications

  • Acute Pain - may be performed during surgery to assist with pain relief afterwards.
  • Chronic Pain - useful for any condition that causes chronic severe upper abdominal visceral pain e.g. chronic pancreatitis - local anaesthetic blocks only.
  • Cancer Pain - useful for upper abdominal organ cancer pain, and is frequently used for carcinoma of the pancreas - initial diagnostic local anaesthetic block, followed by neurolytic block.

Contraindications

  • Bleeding and infection risks.
  • Where the source of the pain is no longer being transmitted through the autonomic nerves e.g. carcinoma of the pancreas that has begun to invade the body wall.
  • It is dangerous to perform the block in the presence of a large aortic aneurysm (swelling of the main down pipe from the heart).

Technique

  • The block is performed using X-ray screening, intravenous sedation , local anaesthetic infiltration of the superficial layers, with the patient in the prone position .
  • Intravenous fluids (plasma expanders 1000 ml) are required pre-block to reduce the risk of the blood pressure falling afterwards.
  • It normally takes two needle insertions, one on each side to block both of the coeliac plexi, but on some occasions good spread to both sides is achieved just using one needle.
  • The needle entry point is just below the tip of the 12th rib , and using X-ray screening in two planes, the needle is advanced until it hits the side of the L1 vertebra.
  • The needle is withdrawn slightly and then re-directed forwards until it is in the area of the coeliac plexus, avoiding the aorta (main down pipe from the heart) and inferior vena cava (main up pipe to the heart).
  • Radio-opaque dye is injected to confirm the correct placement of the needle, and then the appropriate mixture is injected:-
    • For non-malignant pain - 10 ml 0.5% chirocaine on each side
    • For malignant pain - 5 ml 6% aqueous phenol + 5 ml 0.5% chirocaine on each side
  • As the block causes dilation of the upper abdominal vessels, venous pooling can occur with a drop in blood pressure. This can be accentuated by pre-existing dehydration (cancer patients). It is essential therefore that adequate intravenous hydration has occurred before the block commences.

Complications

  • Bleeding due to aorta or inferior vena cava injury by the needle.
  • Intravascular injection (should be prevented by checking the needle position with radio-opaque dye).
  • Upper abdominal organ puncture with abscess / cyst formation.
  • Paraplegia from injecting phenol into the arteries that supply the spinal cord (should be prevented by checking the needle position with radio-opaque dye).
  • Sexual dysfunction (occurs when the injected solution spreads to the sympathetic chain bilaterally).
  • Intra-muscular injection into the psoas muscle.
  • Lumbar nerve root irritation (occurs when the injected solution tracks backwards towards the lumbar plexus).
Lumbar Sympathetic Block

Anatomy

  • The lumbar part of the sympathetic chain lies on the antero-lateral border of the vertebral body . The sympathetic chain is separated from the main lumbar sensory / motor nerves by the psoas muscle.

Indications

  • Poor leg circulation, gangrene of the foot, arterial leg ulcers.
  • CRPS I, CRPS II, Post Herpetic Neuralgia, Phantom Limb Pain.
  • Hyperhidrosis (sweaty feet).

Contra-indications

  • Bleeding and infection risks.
  • It is dangerous to perform the block in the presence of a large aortic aneurysm (swelling of the main down pipe from the heart).
  • A sympathetic block should not be used to treat intermittent claudication (muscle cramp caused by poor arterial supply), as this will cause arterial steal, making the claudication symptoms worse by diverting extra blood flow to the skin.
  • A sympathetic block should not be used to treat erythromelalgia (hot legs / feet caused by arterial thrombosis in small blood vessels due to a high platelet count) - the extra vasodilation will only serve to make the hot legs / feet worse.

Technique

  • The block is performed using X-ray screening, intravenous sedation , local anaesthetic infiltration of the superficial layers, with the patient in the prone position (face down).
  • Using X-ray screening, the needle is inserted about 10 - 12 cm from the midline, and advanced so that initially touches the side of L2 vertebral body. It is then withdrawn slightly and readvanced until it slips past the anterolateral border of the vertebral body .
  • Radio-opaque dye is injected to confirm correct needle position.
  • For diagnostic blocks (CRPS I and CRPS II), 5 - 10 ml 0.5% chirocaine is injected.
  • For neurolytic blocks (arterial insufficiency) 3 - 5 ml 6% aqueous phenol is injected.
  • The same is done for the L3 and L4 levels. Some practitioners treat only L2 and L3 by using a single needle.

Complications

  • Genitofemoral Neuralgia occurs in 5% of all blocks. This causes pain in the L1 groin area and is thought to be due to bruising of the L1 nerve root by the needle passing by it. More than 90% of cases recover spontaneously after 6 weeks. Treatment with amitriptyline and gabapentin / pregabalin can help greatly.
  • Bleeding due to aorta and inferior vena cava injury by the needle.
  • Intravascular injection (should be prevented by checking the needle position with radio-opaque dye).
  • Upper abdominal organ puncture with abscess / cyst formation.
  • Paraplegia from injecting phenol into the arteries that supply the spinal cord (should be prevented by checking the needle position with radio-opaque dye).
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