Chapter 44: Splanchnic Nerve Blocks

INDICATIONS

The splanchnic nerves transmit the majority of nociceptive information from the viscera. Classically performed for patients with intra-abdominal cancer, indications recently have expanded to include:

• Chronic abdominal pain¹

• Chronic pancreatitis pain²

• Differential diagnosis of somatic versus visceral pain³

• Treatment of patients who have failed to obtain relief from celiac plexus blocks³

• Palliation of the acute pain of arterial embolization of the liver for cancer therapy³

• Treatment of pain of abdominal “angina” associated with visceral arterial insufficiency³

CONTRAINDICATIONS

• Local infection

• Sepsis

• Coagulopathy

• Respiratory insufficiency or pleural adhesions (due to risk of pneumothorax)

• Tumors that distort the relevant anatomy

• An abdominal or thoracic aneurism⁴

RELEVANT ANATOMY

• The sympathetic innervation of the abdominal viscera originates in the anterolateral horn of the spinal cord.⁵

• Preganglionic fibers from T5-T12 travel with the ventral roots to join the white communicating rami, pass through the sympathetic chain, and synapse on the celiac ganglia.

• The greater, lesser, and least splanchnic nerves are the major preganglionic of the celiac plexus.

• The greater splanchnic originates from the nerve roots of T5-T10 and travels along the vertebral body, through the crus of the diaphragm, and into the ipsilateral celiac ganglion.

• The lesser splanchnic nerve originates from the T10/T11 nerve roots, while the least splanchnic nerve arises from T10-T12; these also travel through the diaphragm to the ipsilateral celiac ganglion⁶ (Figure 44-1).

• These nerves are bound in a narrow compartment made up of the tibial body and pleura laterally, the posterior mediastinum ventrally, and the pleural attachment to the vertebral body dorsally and the crua of the diaphragm caudally.

• The volume of this compartment is approximately 10 cc on each side.⁷

PREOPERATIVE CONSIDERATIONS

• Documentation of coagulation status and fully informed consent are necessary. Prior to considering neurolysis, the patient should have obtained good but only temporary relief from diagnostic splanchnic blocks, and should be fully aware of the risks of postprocedure diarrhea and orthostatic hypotension form the sympathetic blockade.

• Prior imaging (CT or MRI of the abdomen) should be reviewed preoperatively. Patients usually need sedation, and therefore should be NPO as per the ASA guidelines.

• IV access is mandatory because of the potential hypotension for a successful sympathetic block, and patients are usually pretreated with 500 to 1000 cc of balanced salt solution.

DOCUMENTATION FOR OFF-LABEL INDICATIONS

Because it has traditionally been used only for malignant pain, if the splanchnic nerve block is for chronic, nonmalignant pain, such as chronic pancreatitis, documentation of failure of medication therapy is warranted.