The celiac plexus has also been called the solar plexus, celiac ganglion, and splanchnic plexus (
). It is the largest of the three great plexuses of the sympathetic nervous system in the chest and abdomen: the cardiac plexus innervates the thoracic structures; the celiac plexus innervates the abdominal organs; and the hypogastric plexus supplies the pelvic organs. All three of these plexuses contain visceral afferent and efferent fibers. In addition, they contain some parasympathetic fibers that pass through these ganglia after originating in cranial or sacral areas of the parasympathetic nervous system.
The celiac plexus has also been called the solar plexus, celiac ganglion, and splanchnic plexus ( Fig. 42-1 ). It is the largest of the three great plexuses of the sympathetic nervous system in the chest and abdomen: the cardiac plexus innervates the thoracic structures; the celiac plexus innervates the abdominal organs; and the hypogastric plexus supplies the pelvic organs. All three of these plexuses contain visceral afferent and efferent fibers. In addition, they contain some parasympathetic fibers that pass through these ganglia after originating in cranial or sacral areas of the parasympathetic nervous system.
The celiac plexus innervates most of the abdominal viscera, including the stomach, liver, biliary tract, pancreas, spleen, kidneys, adrenals, omentum, small bowel, and large bowel to the level of the splenic flexure. The celiac plexus receives its primary innervation from the greater, lesser, and least splanchnic nerves, which arise from T5–12. These splanchnic nerves innervate the celiac plexus after traversing the posterior mediastinum and entering the abdomen through the crura of the diaphragm, a variable distance above L1 ( Figs. 42-2 and 42–3 ). These splanchnic nerves are preganglionic and, after synapsing in the celiac ganglion proper (or associated ganglia), their postganglionic fibers radiate to the abdominal viscera ( Fig. 42-4 ). Autopsy examination has shown that the number of ganglia making up the celiac plexus ranges from one to five, with the size of the ganglia ranging from 0.5 to 4.5 cm in diameter.
The celiac plexus is found anterolateral to the celiac artery. Additionally, the vena cava is often anterolateral on the right, the aorta is posterior to the plexus in the midline, the kidneys are lateral, and the pancreas lies anteriorly ( Figs. 42-5 and 42–6 ).
One point of anatomic clarification that is essential for understanding the celiac plexus block is that there are two basic methods of carrying out the block. In the longest-used method, the needles are inserted to perform a deep splanchnic block. This results in spread of the solution (blue area in Fig. 42-7 ), cephalad and posterior to the diaphragmatic crura. The second method involves placing the needle through one crus of the diaphragm from a posterior approach or through the anterior abdominal wall to end up with the needle placed anterior to the aorta in the region of the celiac plexus. As illustrated in Figure 42-7 , this results in solution (pink area in Fig. 24-7) spreading in the vicinity of the celiac artery, anterior to the diaphragmatic crura.
The patient should be positioned for the celiac plexus block in the prone position, with a pillow placed underneath the abdomen to reduce lumbar lordosis.Needle Puncture—Retrocrural Method.
The lumbar vertebral spines, as well as the 12th thoracic vertebral spine, should be identified and marked. Parallel lines are then drawn 7 to 8 cm off the midline, as shown in Figure 42-8 . The 12th rib is palpated, and a mark is placed where the paramedian lines cross the 12th rib bilaterally. Another mark is placed in the midline between the 12th thoracic and first lumbar vertebral spines. Drawing lines between the three marks creates a flat isosceles triangle. The equal sides of this triangle ( Fig. 42-8, A and B) serve as directional guides for the bilaterally placed needles.
Skin wheals are then raised on the marks immediately below the 12th rib, and a 12- to 15-cm, 20- or 22-gauge needle is inserted without the syringe attached, as shown in Figure 42-9 . The needle is inserted 45 degrees off the plane of the table top, directed at the space between the T12 and the L1 vertebral spines. This placement allows contact with the L1 vertebral body at a depth of 7 to 9 cm. If bony contact is made at a more superficial level, it is likely that a vertebral transverse process has been contacted.
When the vertebral body is confidently identified, the needle is withdrawn to a subcutaneous level, and the angle is increased to allow the tip to pass the lateral border of the vertebral body. On the left side (the side of the aorta), once the needle passes off the vertebral body, it should be inserted an additional 1.5 to 2 cm or until the aortic wall is identified by pulsations transmitted through the length of the needle. On the right side, the needle can be inserted 2 to 3 cm after it walks off the vertebral body. It is helpful when inserting the needles to the proper depth to insert the left needle first because it can be advanced slowly until one’s sensitive fingertips (as illustrated in Figure 42-10 ) appreciate the aortic pulsations transmitted up the needle shaft. When this aortic depth is identified, the right needle can then be inserted and readily advanced to a slightly deeper level.
Before local anesthetic or neurolytic agent is injected, the needle should be carefully examined for leakage of blood, urine, or cerebrospinal fluid. If the needle is misplaced, leakage of these fluids should be spontaneous. Injection of local anesthetic solution through the needle should be similar to that experienced when an epidural needle is properly placed. There should be little resistance to injection if a 20- or 22-gauge needle is correctly placed in the retrocrural area.Needle Puncture—Anterocrural Method.
The second basic method of celiac plexus block is the anterocrural approach, which results in the needle tip being placed anterior to the crus of the diaphragm on the right side, as illustrated in Figure 42-11 . To carry out this block, all the foregoing steps are the same, except that the paramedian line on the right is drawn 5 to 6 cm off the midline rather than 7 to 8 cm as in the classic retrocrural approach. The needle is again inserted to strike the vertebral body. Often an angle larger than 45 degrees is necessary to contact the vertebral body initially. When the vertebral body is contacted, the needle is withdrawn and redirected until it walks off the anterolateral edge of the vertebral body. Radiographic assistance is necessary to place an anterocrural needle properly. Commonly, the needle must be inserted 10 to 13 cm to place the needle tip anterior to the crus of the diaphragm. It is helpful to use a supplementary imaging technique for the transcrural approach, as passage of the needle tip through the crus of the diaphragm is difficult to appreciate by palpation unless a transaortic method similar to that of Ischia is used. Once the needle tip is in position anterior to the crus of the diaphragm, local anesthetic solution is injected through the single right-sided needle.
Because of the location of the celiac plexus near the neuraxis, epidural or spinal anesthesia may develop with this technique. Additionally, because of the close relation of the celiac plexus to the aorta, aortic puncture occurs in approximately one third of patients, but it rarely results in serious problems. As with a lumbar sympathetic block, the placement of the needle tip for a celiac block may allow tracking of local anesthetic or neurolytic solution in the region of the lumbar roots, although this also appears to happen infrequently. An even less frequent neurologic injury after neurolytic celiac block, paraplegia, may result from drug-induced spasm of a major lumbar feeding artery (artery of Adamkiewicz). This most likely hypothesis awaits clinical proof.