++
The celiac plexus is a dense matrix of diffuse nerve fibers and
ganglia located around the abdominal aorta and periaortic space
at the level of the T12 and L1 vertebrae. The most distinct feature of
the celiac plexus are the paired semilunar (“celiac”)
ganglia that lie immediately superior to the pancreas in the midline
and are flanked in close approximation by the adrenals. These “paired” ganglia
can actually vary in number and size.18 The aorta
is surrounded by the plexus, which makes this large vascular structure
an important landmark in performing the block. In fact, transgression
of the aorta has been used in identifying needle placement.19 In
addition to the celiac ganglia, the components of the celiac plexus
include the greater, lesser, and least (also called lowest) splanchnic
nerves; there are also contributions from the aorticorenal ganglia
and aortic and superior hypogastic plexus. It is important to realize
that the celiac plexus is not a distinct entity but a diffuse network
that varies in size, network, and position. The most consistent
landmark is the celiac artery because these elements intertwine
around the base of this artery.
++
There are sympathetic, parasympathetic, and visceral afferent
contributions to the celiac plexus. The sympathetic fibers originate
from the thoracic sympathetic chain via the greater and lesser splanchnic
nerves, and the visceral afferents have cell bodies that originate
from the dorsal root ganglion of the spinal cord and travel with
the sympathetic nerves. The parasympathetics originate from the
vagus nerve and sacral nerve roots. The nerves of the celiac plexus
innervate most of the abdominal viscera to include the pancreas,
liver, kidneys, biliary tract, spleen, adrenals, intestines, and
omentum.
++
The celiac plexus block is indicated for patients in pain from
upper abdominal tumors such as pancreatic cancer. Pain relief rates
vary from 70% to 100%, with an average of 85% of
patients that experience at least temporary pain relief.20,21 Pain
from these tumors can be severe, and opioid therapy is often limited
by the sedation and constipation that accompany the high doses required
to manage the patient’s discomfort. Neurolytic celiac plexus
blocks in these patients can provide superior pain relief for up
to 3 to 4 months. In most patients relief will be immediate and effective.
Furthermore, they can lessen the severity of opioid-induced side
effects by decreasing requirements of these drugs. Gastointestinal
motility is also improved by the sympathectomy caused by the block.
The predictive value of a neurolytic celiac plexus block can be
determined by the degree of tumor invasion. Akhan et al22 found
that the grade of tumor as measured by invasion of periaortic and
paracaval fat planes was a good predictor for successful neurolytic
celiac plexus block. Greater than 50% invasion of the fat
planes correlated with little pain relief. Age, history of laparotomy,
chemotherapy, or radiation therapy have not been shown to decrease
the efficacy of neurolytic celiac plexus blocks.
++
Benign conditions such as acute and chronic pancreatitis may
also respond to celiac plexus blocks. As with pancreatic cancer
patients, acute pancreatitis is often resistant to opioid therapy; furthermore,
the disease process may be improved by decreasing the ductal and
sphincter spasm thought to be associated with acute pancreatitis.
Addition of steroids to the local anesthetic injectate has been
shown to decrease the severity of the attack.23 Continuous
catheter techniques can be effective in chronic alcoholic patients
diagnosed with acute pancreatitis who were previously unresponsive
to epidural analgesia. Rykowski et al24 used 0.5% bupivacaine,
20 mL every 6 to12 hours as intermittent injection, or 0.5% bupivacaine
at 6 mL per hour with good results. Using celiac plexus blocks,
especially neurolytic celiac plexus blocks in chronic pancreatitis,
is controversial. While 4 to 6 months of relief can be obtained
from neurolytic celiac plexus blocks, a subset of alcoholic patients
may view their pain-free state as an opportunity to resume their consumption
of alcoholic beverages. Furthermore, because this block also interrupts
the visceral afferents from abdominal organs, it may mask pain related
to intraabdominal emergencies. Benefits to performing celiac plexus
blocks in chronic pancreatitis patients include pain control that
is superior to narcotics and an improved appetite. Often these patients
are malnourished, and analgesia using celiac plexus blocks can improve
their nutritional state by allowing them to eat meals without pain.
The addition of steroids to the injectate has been shown to improve
analgesia without the use of neurolytic agents25 in
the patient with chronic pancreatitis. Regardless of controversy,
celiac plexus blocks have shown to be an effective adjunct in managing
chronic pancreatitis pain.26 Indications for celiac
plexus blocks are summarized in Table 69-2.
++
++
There are a variety of techniques for approaching the splanchnic
nerves or celiac plexus. In general, they can be summarized as posterior
or anterior approaches. The posterolateral approach has become the
most practiced and proven technique by anesthesiologists, whereas
the anterior techniques using computed tomography (CT) or ultrasound
guidance are preferred by invasive radiologists. In all cases, noninvasive
monitoring should be used and an intravenous line should be established.
Intravenous vasoactive agents, volume expanders (crystalloid or
colloids), and sedative and analgesics should be made available
for use as needed.
+++
Posterolateral
Approaches
++
Posterolateral techniques allow access to both the splanchnic
nerves and the celiac plexus. The posterolateral approach is one
originally defined by Kappis and refined by Moore.27 Frequently
used variations of the posterolateral approach include the transcrural
approach, the transaortic approach, and the retrocrural or deep
splanchnic approach.
++
The patient is placed in a prone position with a pillow placed
at the midsection of the abdomen. This minimizes the lumbar lordosis
and aids in patient comfort. Occasionally, the abdominal pain can
be so severe that the prone position is not tolerated, and analgesics
must be used or the patient must be positioned in the lateral decubitus
position. The arms are underneath behind the head or allowed to
hang off the table. An intravenous line is placed to provide light
sedation if necessary, and a 200 to 500 mL crystalloid bolus is
administered to offset the sympathectomy-induced hypotension caused
by the block. Anatomic landmarks are identified and marked in ink.
Agents typically used for the celiac plexus block include 0.25% to
0.5% bupivacaine (with or without 80-mg methylprednisolone
or equivalent), 6% to 10% phenol, or 50% to
100% alcohol. Volumes are described for each technique
(see following sections).
++
The classic posterior approach is a two-needle technique; needle
placement is similar for both sides. Landmarks include the 12th
ribs and the T12 and L1 spinous processes; fluoroscopic or CT guidance
helps with landmark identification and minimizes complications during
needle placement and injection. A shallow isosceles triangle is
formed by these three points. The lateral points should lie 6 to
9 cm from the midline and usually correspond to the junction of
the paraspinal muscles and the 12h rib. After administering local
anesthetic to create a skin wheal at this point, a 12- to 15-cm,
20- to 22-gauge subarachnoid needle is inserted percutaneously and
angled at 45 degrees to the coronal plane and about 15 degrees cephalad.
The needle is advanced until contact with the lateral body of L1
is made. This typically occurs at the depth of 8 to 10 cm; if bony
contact is made at a more shallow depth than this, it is likely
that the transverse process has been encountered. The needle is
then withdrawn (almost subcutaneously) and the needle tip is redirected
laterally an additional 10 degrees and readvanced; this next attempt
should contact bone about 2 to 3 cm deeper than the previous attempt.
This maneuver is repeated until the needle is “walked off” the
lumbar body (Fig. 69-4). The final placement of the needle tip is
1.0 to 1.5 cm anterior to the vertebral margin. If the first needle
was placed on left side, correct needle placement is confirmed by
observing the needle pulsate on visual inspection and tactile analysis.
Needle pulsation occurs because the final position of the needle
tip is often close to the aorta. The second needle is placed on
the right side using the same technique as the first; depth is guided
by the final needle depth used on the left side. Fluoroscopy can
be used to confirm tip placement; spread of contrast agent seen
on fluoroscopy will indicate retrocrural, transcrural, transaortic,
or intradiaphragmatic injection of agent (Figs. 69-5 and 69-6).
If CT imaging is used, needle paths are traced from the skin to
the celiac plexus to avoid injury to renal or vascular structures.
++
++
++
++
For the transcrural approach, advancing the needle tips an additional
1 to 2 cm will pierce the diaphragmatic crus and place the needle
tip anterior to the diaphragm. A loss of resistance is usually felt
as the crus is pierced. The anteroposterior (AP) and lateral radiographs
with contrast will show a linear spread in the left lateral preaortic
area. If contrast spread is predominately cephalad and appears to
collect around the L1 vertebral body, the needle tip is likely to
be retrocrural. Lateral radiographs can confirm that the contrast
is posterior and superior to the diaphragm, also suggesting retrocrural
spread. The procedure can then be performed as a deep splanchnic
nerve block (see later section), or the needle is advanced to pierce
the diaphragmatic crus (thus transcrural). If muscle striations
are seen following contrast injection, the needle tip is likely
contained within diaphragmatic muscle, and should be advanced about
1 cm. On lateral fluoroscopy, contrast agent is typically seen to
spread in a cranio-caudal direction anterior to the vertebral body,
but agent spread is limited to below the diaphragm (see Fig. 69-5B,
contrast patttern, and Fig. 69-6B). Following negative aspiration
of each needle, 15 to 25 mL of local anesthetic or neurolytic agent
is injected through each needle in divided doses.
++
The transaortic approach is a single needle, left-sided technique
that is also transcrural.19 The intent of this
approach is to pierce the aorta with the needle to ensure that the
needle tip is anterior to the aorta. Placement of the injectate
anterior to the aorta can minimize the risk of neurologic complications
caused by unintended spread of neurolytic agents to the lumbar plexus. Needle
placement is the same as for the transcrural approach, but the needle
is advanced until aortic wall penetration occurs and free-flowing
blood is aspirated. The needle is then advanced further through
the anterior wall of the aorta until no blood is aspirated.
++
A 5-mL loss of resistance syringe filled with saline can be used
to identify anterior aortic wall penetration. Once blood is aspirated
through the block needle, the loss of resistance syringe is attached
to the needle and constant pressure is applied to the syringe plunger.
A resistance to injection will be felt once the anterior aortic
wall has been contacted, followed by loss of resistance once the
needle tip has entered the anterior periaortic space. Following
negative aspiration, contrast agent is injected and will appear
anterior to the vertebral bodies (see Fig. 69-5C and Fig. 69-6A).
Local anesthetic, steroid, or neurolytic agent is then injected.
A smaller total volume of agent (20 to 25 mL) is used for this technique.
++
With the anterior approach, a 12- to 15-cm, 22-gauge needle is
passed through the midline epigastrium until the body of L1 is contacted.
The needle is then withdrawn 1.0 to 1.5 cm and placement is confirmed
using fluoroscopy, ultrasound, or CT imaging.28,29 Patient
comfort is a major advantage to this approach, especially when the
patient is unable to lie prone. Only one needle is used with this
technique, so there is less pain from posterior two-needle approaches.
Furthermore, the risk of needle-related injury to motor nerves is
significantly reduced compared to posterior approaches.
+++
Splanchnic Nerve
Blocks
++
An alternative technique to achieve abdominal sympathectomy and
visceral nerve block is the splanchnic nerve block. The splanchnic
nerve block specifically interrupts the sympathetic imput to the
celiac plexus without blocking the abdominal parasympathetics. The
final position of the needle tip is superior to the diaphragm; the
intention is to block the greater, lesser, and least splanchnic
nerves before they traverse the diaphragm into the abdomen. The
advantages of performing sympathectomy and visceral nerve block
are multifold. Gastrointestinal motility is improved compared with
the celiac plexus block because the parasympathetics (which join
the splanchnics at the level of the celiac ganglia) are left unopposed.
Also, because the lumbar sympathetics are not blocked by this technique,
hypotension is decreased. Lastly, with the classic splanchnic nerve
block, a smaller volume of local anesthetic or neurolytic agent
can be used (3 to 4 mL per side).
++
For the deep splanchnic approach30,31 (also
known as the retrocrural celiac plexus block), landmarks and needle
approach are similar to the transcrural celiac plexus block. The
needle is walked off the vertebral body and advanced until the needle
pulsates (due to the proximity of the needle tip to the aorta) on
visual inspection and tactile analysis. When the block is performed
correctly, 3- to 5-mL injection of contrast will remain within the
retrocrural space and migrate primarily cephalad (see Fig. 69-5A).
On fluoroscopic AP view, the contrast will be confined along the
lateral border to the L1 vertebral body (see Fig. 69-6A). On lateral
view, layering of the contrast in a narrow line along the anterior
vertebral column should be seen. The procedure is then repeated
on the right side. Fifteen milliliters of local anesthetic or neurolytic
agent are injected through each needle. Parasympathetics and the lumbar
sympathetic chain are not blocked with this technique.
++
The classic splanchnic nerve block is performed in a manner similar
to the deep splanchnic approach, but the needle is directed toward
the anterolateral margin of T12 vertebral body. A paramedian approach
is used, inserting two 7- to 10-cm needles 3 to 4 cm lateral to
the midline just below the 12th ribs, then directing the needle
tips toward the T12 body. Radiographic contrast patterns are similar
to the deep splanchnic nerve block. The disadvantages of this block
relate to final position of the needle tips; compared with the transcrural
and transaortic blocks, the needle tips lie posterior and cephalad
to the diaphragm, which increases the risk of chylothorax and pneumothorax.
++
The incidence of major complications with neurolytic celiac plexus
blocks is 0.15 to 1.0%.32,33 These complications
typically occur from transgression of structures during needle placement
or unintentional spread of neurolytic or local anesthetic solutions.
Inadvertent injury to structures can result in pneumothorax, chylothorax
(secondary to thoracic duct injury), genitourinary injury, somatic
nerve injury, and retroperitoneal hematoma; complications secondary
to inadvertent spread of agent include sexual dysfunction, groin
neuralgia, paraplegia, retroperitoneal fibrosis following repeated
neurolytic blocks,34 and pleural effusion.35 Complications
are often self-limited. In a study of 136 cases following celiac
plexus block, Brown et al describes two cases of pneumothorax, neither
requiring thoracostomy as therapy.21 Renal perforation
can occur, albeit typically without sequelae, especially if the block
needles are placed more than 7.5 cm from midline. When inserted
lateral to this point, renal impalement can occur in 10% of
cases.36 Paraplegia has been described secondary
to injury to the artery of Adamkiewicz during block placement37 and
from arterial vasospasm causing anterior spinal artery syndrome.38 Paraplegia
can also occur from incorrect needle placement and subsequent injection
in the subarachnoid or epidural space, or from intrapsoas muscle
injection with blockade or neurolysis of the lumbar plexus. Radiographic
imaging (biplanar fluoroscopy or CT) can minimize these risks.
++
Minor sequelae inherent to the celiac plexus block are relatively
common. The most common side effects of the block include local
pain (96%), hypotension (38%), and diarrhea (44%).32 Systolic blood
pressure decreases of 30 to 40 mm Hg are not uncommon and are usually
seen when the patient assumes an upright or sitting position following
celiac plexus block. The hypotension is caused by blood pooling
in the splanchnic vessels following sympathectomy; this can be minimized
by an intravenous fluid bolus at the time of block placement. Compensatory
reflexes usually appear by 48 hours. Diarrhea is thought to be caused
by unopposed parasympathetic activity: impairment of α-adrenergic
stimulation to enterocytes that increase intestinal secretory activity
as well as decrease absorptive processes may also play a role. Intractable
diarrhea may respond to clonidine patches or to octreotide 0.1 mg
subcutaneously twice a day.39,40 The increase in
gastrointestinal activity can be used in a therapeutic manner. Weinstabl
et al used bupivacaine celiac plexus blocks to reduce the intestinal
dysfunction (as measured by decreased gastric volumes) in several
patients in a neurosurgical intensive care unit.41 Nausea
and vomiting can occur from the hypotension caused by the block,
or from alcohol intoxication when excessive amounts of neurolytic
alcohol are absorbed at the block site. Chest pain can also occur
after celiac alcohol block. It usually resolves within an hour.42