Splanchnic Nerve Block - An Insight

What Are Splanchnic Nerves?

The greater, lesser, and least splanchnic nerves are located in the thorax. These nerves originate from sympathetic chain branches and travel down the sides of the lower and middle thoracic vertebral bodies, emerging through the diaphragm's posterior aspect. The genesis and course of these nerves vary significantly. The majority of the abdominal organs receive sympathetic innervation via postganglionic fibers that originate from their synapses in different prevertebral ganglia.

The breakdown of the splanchnic nerves, their ganglia of origin, and their synapses:

• The greater splanchnic nerve arises from thoracic ganglia 5 through 9 and synapses in the celiac ganglion. Some fibers bypass this ganglion and directly innervate the adrenal gland's medulla.

• The lesser splanchnic nerve originates from thoracic ganglia 10 and 11. It synapses in the aorticorenal ganglion.

• The least splanchnic nerve originates from thoracic ganglion 12 and synapses within the ganglia of the renal plexus.

Which Areas Are Affected by the Splanchnic Nerve Block?

Abdominal pain that may not respond to medication or other therapies can be treated with a splanchnic nerve block, which entails injecting an anesthetic drug into a group of nerves. From the spinal cord, the splanchnic nerves migrate to the celiac plexus (nerve bundle in the upper abdomen region behind the pancreas), where they affect functions related to the abdomen. The stomach, kidneys, small intestine, gallbladder, pancreas, liver, adrenal gland, and spleen are among the abdominal organs from which they send pain signals to the brain via the spinal cord. A splanchnic nerve block provides comfort for patients with chronic pancreatitis (inflammation of the pancreas), cancer-related stomach pain, or both.

What Are the Indications and Contraindications of Splanchnic Nerve Block?

The splanchnic nerves are responsible for transmitting the majority of nociceptive (pain) information from the viscera. Originally performed for patients with intra-abdominal cancer, the indications have recently expanded to encompass:

• Chronic abdominal pain.

• Chronic pancreatitis pain.

• Differential diagnosis of somatic versus visceral pain.

• Treatment of patients who have not found relief from celiac plexus blocks.

• Palliation of acute pain from arterial embolization of the liver for cancer therapy.

• Treatment of abdominal "angina" pain associated with visceral arterial insufficiency

• However, there are certain contraindications, including local infection, sepsis (body's extreme reaction to infection), coagulopathy (clot formation is impaired), respiratory insufficiency or pleural adhesions (due to the risk of pneumothorax), tumors that distort relevant anatomy, and abdominal or thoracic aneurysms (bulge in the aorta).

What Is the Equipment Used for the Splanchnic Nerve Block?

• Standard ASA monitoring equipment- pulse oximeters, electrocardiography, blood pressure device, and monitor temperature.

• Utilization of fluoroscopy (body movements video by passing X-rays).

• Sterile preparation and draping.

• Administration of skin local anesthesia before using needles larger than 25 G (gauge) (unless sedation is applied).

• Adoption of coaxial view for needle advancement unless specified otherwise.

• Availability of cardiopulmonary resuscitation (CPR) equipment and medications.

• Diagnostic injection with a 22 G (gauge), 3.5 inches (90 millimeters) to 7 inches (180 mm) needle, curved tip.

• Radiofrequency ablation (a minimally invasive technique used to reduce nodule and tumor and other growth sizes) using an 18 to 20 G, 3.5 inches (90 mm) to 7 inches (180 mm) curved tip cannula with a 10 mm active tip.

• Grounding pad for safety.

• A radiofrequency ablation generator is capable of unipolar and bipolar lesion creation.

• Pre-procedure infusion of 500 ml (milliliters) fluid.

• Administration of local anesthetic.

• Use of nonionic contrast.

What Is the Procedure of a Splanchnic Nerve Block?

• The patient will be positioned on their stomach, and local anesthesia will be injected to numb the skin, ensuring comfort during the procedure. Intravenous sedation may also be administered to induce a calm and relaxed state.

• Initially, a temporary nerve block using anesthetic is applied to the splanchnic nerves to assess its effectiveness in relieving the patient's pain. Bilateral insertion of a needle occurs at the 11th thoracic vertebra, followed by verification of proper positioning using fluoroscopy (X-ray with dye for visualization). Subsequently, an anesthetic is injected into the nerves.

• This local medication numbs the splanchnic nerves, preventing the transmission of pain signals to the brain. Typically, this procedure takes less than thirty minutes. A successful splanchnic nerve block is evidenced by significant pain relief.

• People experiencing proven pain relief from a block involving local anesthetic injected into the splanchnic nerves are suitable candidates for a more lasting nerve block. Injecting alcohol into these nerves reduces their ability to transmit pain signals, potentially offering two to three months of pain relief. Following this, local anesthetic is injected, and radiofrequency ablation is targeted at the splanchnic nerves. This method specifically targets a precise area, typically without adverse effects on neighboring tissues and nerves, leading to prolonged pain relief.

• Usually, the procedure takes about 45 minutes. The patient can normally go home the same day.

What Are the Benefits of Splanchnic Nerve Block?

After undergoing a splanchnic nerve block, many patients experience unmanageable, chronic abdominal pain related to cancer or inflammation and often describe experiencing significant pain relief. This improvement enables them to lead a more active and independent lifestyle, enhancing their quality of life. Moreover, a splanchnic nerve block can decrease reliance on opioid medications and alleviate associated side effects like constipation, drowsiness, and confusion.

What Are the Risks of Splanchnic Nerve Block, and What Regions Must Be Protected During Nerve Block?

The splanchnic nerve block is generally viewed as a low-risk, minimally invasive procedure. Although rare, potential complications may include infection at the injection site, needle misplacement leading to bleeding or pneumothorax (lung collapse), hypotension (low blood pressure), increased bowel movements or diarrhea, and allergic reactions to medication. Typically, these issues are resolved within three days.

• Thoracic nerve roots → nerve injury.

• Intercostal blood vessels and nerves → nerve injury, bleeding.

• Intervertebral disc → discitis.

• Lung or pleura → pneumothorax.

• Thoracic duct → chylothorax (lymph developed in digestive system (chyle) accumulation in the chest).

• Diaphragm → hemidiaphragmatic paralysis.

• Aorta or inferior vena cava → bleeding, local anesthetic toxicity.

• Segmental or intercostal artery, possibly feeding the anterior spinal artery → spinal cord injury or ischemia.

• Infection.

• Bleeding.

• Postprocedure pain.

• Vasovagal reaction (drop in heart rate and blood pressure causes fainting).

• Allergic reaction.

• Hypotension caused by splanchnic vasodilation (widening of blood vessels).

Conclusion:

This research affirms that splanchnic nerve neurolysis alleviates pain intensity, reduces opioid consumption, and enhances functional status and quality of life among patients experiencing pain from upper abdominal malignancies with distorted celiac anatomy. However, to solidify these findings, a sizable randomized controlled trial with sufficient sample size and extended follow-up duration is essential.