CELIAC PLEXUS BLOCK

Celiac plexus lies anterior to the aorta at the level of the first lumbar vertebra, between the origin of celiac and superior mesenteric arteries The adre nal glands lie lateral to the plexus and  stomach and pancreas lie anteriorly. The connections include Preganglionic sympathetic fibres from splanchnic nerves, Preganglionic parasympathetic from vagus, Sensory fibres from phrenic and vagus, Afferent fibres concerned with nociception
The three pairs of splanchnic nerves descending to the celiac plexus are
 1) Greater splanchnic nerves from T5-T9
 2) Lesser splanchnic nerves from T10 and T11 segments
 3) Least splanchnic from T12

The three pairs of ganglia in the plexus are 

 1)Celiac ganglia

  2)Superior mesenteric ganglia
  3)Aorticorenal ganglia

The nociceptive afferent fibres travel from viscera along with the sympathetic fibres, through the ganglia, splanchnic nerve, sympathetic chain, white rami communicans and then synapse in the dorsal root ganglia.The proximal axon of these bodies synapse in the dorsal horn of the spinal cord

The blockade of the celiac pleexus causes blockade of pain transmission from the visceral structures including Pancreas, Liver, Gall bladder, Omentum, Mesentery, Alimentary tract, and complete blockade of the Sympathetic fibres causing increased Parasympathetic activity manifested as increased intestinal motility and relaxed sphincters. The sympathetic blockade to the splanchnic vessels cause vasodialatation and hypotension

Agents used for blockade are 0.5% bupivacaine with adrenaline1:200000 around 30ml, 15 ml on either side with or without steroids(dexamethasone) for chronic pain. Neurolytic blockade is indicated in abdominal malignancies where alcohol 50-100% or 10% phenol is used. The pain on injection of alcohol can be minimised with combination of bupivacaine 1:1 ratio

 Indications:

• Pain relief in upper abdominal malignancies from stomach, pancreas, gall blader, and liver.(Indication for neurolytic block)
• Pain after multiple abdominal surgeries. Local anesthetic and steroids indicated.
• For evaluation of upper abdominal pain, local anaesthetic alone used
• Chronic inflammatory conditions like chronic pancreatitis, neurolytic block advised.

Technique
 1) Informed consent
 2) IV access monitors
 3) Prone position with pillow beneath hip to minimise lumbar lordosis

Classic approach: Mark the inferior edge of T12 (A) and L1 spinous processes and the inferior edge of the 12th rib at a point 7-8cm lateral of the midline(points B and C). Connect these points to form a triangle, the base of which is passing over the inferior edge of the L1 spinous process
 
Aseptic preparation of the skin, infiltrate the skin and muscle with local anaesthetic use a 12-18 cm long ,20-22 gauge needle and introduce(the left side needle first) at a 45degree angle relative to the sagittal plane running through the spine. The direction is towards the L1 spine and proceeds to hit on the L1 vertebral body.(more superficial bony contact may be the L1 transverse process)The needle contacts the L1 vertebral body at a depth of. 7-10 cm. A skin marker is placed on the needle. The needle is then withdrawn deep to the subcutaneous plane and re introduced laterally until it just slips from the lateral border of the vertebral body Slowly advance the needle further, feeling for the transmitted pulsations of the aorta and stop advancing once pulsations are felt. On the right side advance further 1 cm.

Lateral X-ray taken and a negative aspiration test for blood done.A test dose containing 2-3 mlof local anae sthetic with adrenaline is given to exclude intravascular or sub arachnoid placement. Inject 20-25 ml local anaesthetic through each needle. Fluroscopy or CT scan guidance may be undertaken for high precision in case of therapeutic blocks.The signs of successful block is hypotension and the patient may feel an urge to empty bowel.

 Paramedian approach: Needle is inserted caudad to 12 th spinous process at a point 3 cm lateral to the midline in a plane perpendicular to the skin

 
Anterior approach: Through the anterior abdominal wall under fluoroscopic and ultrasound guidance.

 Direct block: Retroperitoneal surgeries, pancreatectomy or whipples resection block given by surgeon for post op analgesia or neurolytic block for malignant conditions.

Endoscopic Ultrasound Guided Method: See Ref: below.

Complications:

• Hypotension due to sympathetic blockade minimised by giving 500-1000 ml of RL before the block.
• Orthostatic hypotension may persisit after a neurolytic block for about one week.but self limiting.
• Other complications are back ache due to retroperitoneal hamatoma or injury to lumbar plexus, injury to kidney, bowel, retroperitoneal hematoma ,intrathecal injection, pneumothorax.,infection, aortic dissection, paraplegia or local anaesthetic toxicity.

Ref: An endoscopic ultrasound guided technique(Michaels AJ, Draganov PV, Endoscopic ultrasound guided celiac plexus block... World J gastroenterology2007:13(26):3575-80)
Wylie Churchil Davidson Practise of Anaesthesia Seventh edition pp1261-62

Michael Mulroy,Christopher Bernards, et al; A Practical approach to Regional Anaesthesia, Fourth Edition