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The autonomic nervous system includes the sympathetic and parasympathetic divisions. The lumbar sympathetic block is a procedure aimed at stopping the nerve supply from the sympathetic chain to the lower limbs. It facilitates in controlling pain mediated by the sympathetic system. Lumbar sympathetic blocks are widely used in helping to relieve different types of pain such as Complex Regional Pain Syndrome, phantom limb pain, hyperhidrosis, painful vascular insufficiencies, or pain associated with herpes zoster.


The sympathetic trunk comprises a bundle of nerves extending from the base of the skull to the coccyx. Its primary function is to regulate the body's "fight or flight" response and aids in maintaining balance alongside the parasympathetic nervous system. The lumbar sympathetic trunk is situated along the front and side of the first to fourth lumbar vertebrae. Preganglionic neurons exit the spinal cord through white rami of the ventral roots of spinal nerves L1 to L4 and then connect at the appropriate lumbar sympathetic ganglion. Postganglionic neurons extend downwards from there to innervate specific areas. The most densely packed lumbar sympathetic ganglia are found in L2 and L3, making lumbar sympathetic blocks typically performed around the lower third of L2 or the upper third of L3.

Lumber Sympathetic Block

Critical Structures and Safety Precautions in Lumbar Sympathetic Block:

During lumbar sympathetic block procedures, several critical structures need careful consideration to minimize potential complications. Firstly, attention must be paid to the exiting nerve roots, particularly spinal nerves L1 to L4, to avoid inadvertent injury which could lead to sensory or motor deficits. Additionally, intraspinal structures such as the spinal cord and epidural space should be carefully navigated to prevent damage and minimize the risk of spinal cord injury or epidural hematoma formation. The genitofemoral nerve, which innervates the genitals and upper thigh, should also be safeguarded to prevent post-procedural sensory disturbances. Intervertebral discs are vulnerable to infection (discitis) if inadvertently penetrated, necessitating sterile technique and precise needle placement. Given the proximity to vital structures like the kidneys, ureters, and inferior vena cava, particularly on the right side, the risk of bleeding should be carefully managed to prevent significant haemorrhage or injury. Furthermore, vigilance against local anaesthetic toxicity is crucial to avoid systemic complications. Lastly, attention should be paid to segmental arteries to prevent bleeding complications during needle placement or injection. Overall, meticulous attention to anatomy and technique is essential to mitigate the risks associated with lumbar sympathetic block procedures.

Indications for Lumbar Sympathetic Blocks:

1.      Complex Regional Pain Syndrome (CRPS): Characterized by dysregulation of the central and autonomic nervous system leading to uncontrolled pain and temperature abnormalities in the affected extremity.

2.     Lower Limb Painful Ischemia: Useful in patients with lower limb ischemia due to vascular disease who are not suitable candidates for surgery, helping to alleviate pain, promote wound healing, and potentially prevent limb amputation by disrupting sympathetic innervation and improving blood flow.

3.     Phantom Limb Pain: Effective in relieving pain perceived in a limb that has been amputated, though the exact mechanism is not fully understood.

4.    Neuropathic Pain:

5.     Postherpetic Neuralgia: Offers improvement in pain, function, and quality of life for patients experiencing postherpetic neuralgia secondary to shingles (zoster).

6.    Hyperhidrosis: Beneficial in managing excessive sweating (hyperhidrosis).

7.     Raynaud Disease: Helps alleviate symptoms associated with Raynaud disease, a condition causing episodes of reduced blood flow to the extremities, typically triggered by cold or stress.

8.    Cancer Pain: Can be utilized as part of pain management strategies for patients suffering from cancer-related pain.

Contraindications to Lumbar Sympathetic Blocks:

1.      Patient on Anticoagulant Therapy: Patients who require continuous anticoagulant therapy for medical reasons cannot undergo lumbar sympathetic blocks due to the increased risk of bleeding complications.

2.     Coagulation Abnormalities: Individuals with conditions affecting blood clotting, such as bleeding disorders, are not suitable candidates for lumbar sympathetic blocks due to the heightened risk of bleeding.

3.     Medication Allergies: Patients with known allergies to any of the medications used during the procedure should not undergo lumbar sympathetic blocks to avoid potential allergic reactions.

4.    Uncontrolled Diabetes: Patients with poorly managed diabetes are not appropriate candidates for lumbar sympathetic blocks due to the potential exacerbation of their condition.

5.     Poorly Controlled Heart Disease: Individuals with inadequately managed heart disease should avoid lumbar sympathetic blocks due to the possible cardiovascular risks associated with the procedure.

6.    Patient Refusal: If a patient declines to undergo the procedure, regardless of the reason, lumbar sympathetic blocks should not be performed.

Equipment and Monitoring for Lumbar Sympathetic Blocks:

For the safe and effective administration of lumbar sympathetic blocks, various equipment and monitoring measures are essential. Standard American Society of Anaesthesiologists (ASA) monitoring is employed throughout the procedure to monitor vital signs and ensure patient safety. Fluoroscopy is utilized to provide real-time imaging guidance during needle placement. Before the procedure, sterile preparation and draping are conducted to maintain aseptic conditions. Local anaesthesia is administered to the skin before inserting any needle larger than 25 gauge unless sedation is utilized. A coaxial view is consistently employed to guide the advancement of the needle unless otherwise specified. Cardio-pulmonary resuscitation (CPR) equipment and necessary medications are readily available in case of emergencies. Specific needles and cannulas, ranging from 20 to 22 gauge and 5 to 7 inches in length, are utilized for diagnostic injections and radiofrequency ablation (RFA), respectively. Local anaesthetics and non-ionic contrast media are employed during the procedure. Intravenous (IV) access is established pre-emptively to address any potential hypotensive episodes. Additionally, peripheral skin temperature monitoring equipment is utilized, particularly for lower extremities, to assess the effectiveness of the procedure and ensure patient comfort and safety.

Drugs Required for Lumbar Sympathetic Block:

For diagnostic purposes, a short-acting local anaesthetic such as 1% Lidocaine Hydrochloride Injection, USP, is commonly employed. An injection volume of 15 to 25 millilitres is required.

Lidocaine provides temporary pain relief, aiding in the diagnosis of conditions like complex regional pain syndrome. When aiming for neurolytic blockade to achieve longer-lasting pain relief, solutions containing 6 to 10% phenol, or 50 to 100% alcohol are utilized. These solutions are injected in volumes of 2 to 4 millilitres at L2, L3 and L4 levels. Phenol and alcohol work by disrupting the function of sympathetic nerves, offering sustained relief from chronic pain conditions. 

Preparation for Lumbar Sympathetic Block:

Before starting the lumbar sympathetic block procedure, it's important to take a moment to ensure everything is in order. This includes confirming the patient's identity, discussing what we're going to do, and making sure we're working on the correct side of the body. The patient lies down on the fluoroscopy table facing downwards. Some doctors may give the patient a little sedation through an IV to help them relax. Once we know where we're going to inject, we clean the area well with a betadine solution and cover it with a sterile cloth. After making sure the patient is comfortable and the area is clean, we can begin the procedure.

Technique -

For a lumbar sympathetic block, the patient is typically placed in the prone position, with a pillow under their abdomen to reduce lumbar lordosis. The skin on the back is cleaned with an antiseptic solution and numbed with a local anaesthetic.

Ensure that the C-arm of the fluoroscope is positioned correctly so that you can see the L2, L3, and L4 vertebrae and their alignment (Squiring) should be at the level where the procedure will be performed. Ensure that the C-arm of the fluoroscope is positioned correctly so that you can see the L2, L3, and L4 vertebrae and their alignment should be at the level where the procedure will be performed.

Lumber Sympathetic Block

Next, position the C-arm at an oblique angle so that the end of the transverse process aligns with the front of the vertebral body, avoiding the transverse process during needle insertion. Aim the needle towards the front of the L2 or L3 vertebral bodies. Sometimes, the block is done at both levels.

Inject local anaesthesia at the planned entry point. Progress the Needle under Tunnel View.

Lumber Sympathetic Block

Lumber Sympathetic Block

Lumber Sympathetic Block

Lumber Sympathetic Block

Lumber Sympathetic Block

Use a lateral image to check the needle's depth. Adjust it to the anterolateral corner of the vertebral body.  Check The Needle in AP View.

After confirming correct needle placement and ensuring no air, blood, or cerebrospinal fluid is aspirated, inject 1 mL of contrast to check flow and position. You should see the contrast covering the front of the vertebral body, spreading up and down between L1 to L3.

Once confirmed, inject the medication (like anaesthetic bupivacaine 0.5%, ethanol 96%, or botulinum toxin) to complete the lumbar sympathetic block. Remove the needle, apply pressure to the entry point, and cover it with a bandage.

A successful block is indicated by a 2–3-degree Celsius rise in temperature in the affected limb. The skin of the injected limb may also appear flushed due to blood vessel dilation.

Complications of Lumbar Sympathetic Block:

Complications of lumbar sympathetic block can be categorized into several groups:

1.      Neurological Complications:

  • Simultaneous Blockade of L2 Somatic Nerve Root: This can lead to motor weakness or sensory deficits in the lower extremities.

  • Inadvertent Injection into the Subarachnoid Space: This may result in spinal cord injury or cerebrospinal fluid leak, leading to headaches or neurological deficits.

  • Damage by Needle or Neurolytic Solution to Adjacent Structures: This includes potential harm to the kidneys, renal pelvis, ureters, or intervertebral discs, leading to pain or dysfunction in these areas.

2.     Vascular Complications:

  • Inadvertent Injection into Vessels: Injection into the vena cava, aorta, or lumbar vessels can lead to vascular injury, thrombosis, or embolism.

3.     Infection:

  • Infection at the Injection Site: This may result in local inflammation, abscess formation, or systemic infection if left untreated.

4.    Hematological Complications:

  • Retroperitoneal Hematoma: Hemorrhage into the retroperitoneal space can occur due to vascular injury during the procedure, leading to pain, hypotension, or organ compression.

5.     Sympathetic System Complications:

  • Destruction of Sympathetic Fibers: This can lead to various symptoms, including cramping or burning pain in the anterior thigh, as well as disruption of sympathetic regulation.

  • Sympathectomy-Mediated Hypotension: Loss of sympathetic tone may result in orthostatic hypotension or vasovagal reactions.

6.    Reproductive Complications:

  • Failure of Ejaculation: Disruption of sympathetic innervation to the reproductive organs can lead to ejaculatory dysfunction or infertility in males.

Overall, while the lumbar sympathetic block can be an effective treatment for certain conditions, it carries the risk of various complications, ranging from neurological and vascular injuries to infections and disruptions of sympathetic function. Close monitoring and appropriate techniques are crucial to minimize these risks.

To ensure a successful procedure and minimize risks, clinicians should be aware of certain clinical pearls:

1.      Anatomical Variations: The anatomy of the lumbar sympathetic ganglion can vary significantly among individuals. This includes variations in the location, size, and branching patterns of the ganglion and associated nerves. Clinicians should carefully review imaging studies such as CT scans or fluoroscopy to identify any anatomical anomalies that may affect the procedure. Adjustments to the approach may be necessary to avoid inadvertent injury to adjacent structures.

2.     Tailored Approach: In some cases, the path to the lumbar sympathetic ganglion may be obstructed by transverse processes or other anatomical structures. Clinicians should be prepared to adapt their targeting technique to navigate around these obstacles safely. This may involve using imaging guidance such as fluoroscopy or ultrasound to visualize the target site and adjust the needle trajectory accordingly.

3.     Anatomical Variability: Even within the same individual, the position of the lumbar sympathetic ganglion can vary from one side to the other. Additionally, the distance between the ganglion and the site of needle insertion may differ between patients. Clinicians should be flexible during the procedure and prepared to adjust their technique based on individual anatomical variations.

4.    Multilevel Approach: Targeting multiple levels of the lumbar sympathetic chain can enhance the efficiency of sympatholysis, especially in cases where pain or sympathetic dysfunction affects multiple segments of the lower extremities. By blocking sympathetic outflow at multiple levels, clinicians can achieve more comprehensive pain relief and functional improvement.

5.     Monitor Lower Limb: Following the lumbar sympathetic ganglion block, it is essential to monitor the lower limb for signs of successful sympatholysis. This may include tracking changes in skin temperature, observing alterations in skin color or texture, and assessing changes in pain intensity or distribution. Successful sympathectomy should result in vasodilation and increased blood flow to the affected limb, leading to improvements in temperature and skin condition.


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