Position and anatomical landmarks
The intervention is performed under X-ray guidance. The patient is placed in a prone position on a translucent table with a pillow underneath the abdomen in order to reduce lumbar lordosis. Prior to the procedure, an intravenous infusion line is placed and an ECG and saturation monitoring are installed. Moreover, the patient is provided with a nose prong with 3 litres O2. The procedure takes place under sedation with propofol or remifentanyl and spontaneous respiration.
Procedure
Th12 en L1 are identified in the posterior anterior view, and the end plates are aligned (Figure 1). De C-arm is rotated 5º to 10° to the side that is being treated. The patient is asked to breathe in and out deeply. The attachment of the diaphragm is noted at mid-Th12 level. The needle placement site is located where the rib is attached to vertebrae Th11 and Th12, and above the diaphragm. The site is marked with a marker and the skin and deeper layers are infiltrated with 5 ml local anaesthetic (e.g., lidocaine 2%) with a 22-G needle.
Figure 1. RF treatment of the splanchnic nerve Th11: AP view.
Treatment is performed with a 10-15 cm 22-G blunt or sharply bent
type of needle with a 10-mm active tip. As these patients are often
very thin, a 10-cm needle is usually long enough. The blunt
needle has the advantage of there being less chance of a collapsed
lung. Its disadvantage is difficult penetration of the skin, which
is why a classic intravenous 14-G catheter (introduction needle) is
first inserted using perfect tunnel view, aiming for a needle
position just next to the corpus vertebrae. When two-thirds
of the catheter has been inserted into the patient, the stylet is
removed and the needle depth is checked in the lateral view. The
needle must remain posterior to the intervertebral foramen.
The C-arm is repositioned using tunnel vision and the RF cannula is
inserted. While maintaining tunnel vision, the cannula is
shifted further.
Initially, the curve of the tip of the needle is rotated externally in order to prevent it penetrating the intervertebral foramen. Once the needle has passed the intervertebral foramen, it must be turned medially in order to maintain close contact with the vertebral body.
Figure 2. RF treatment of the splanchnic nerve at level Th11: lateral view.
Regular checking of the depth of the needle (each 0.5 cm) in the lateral view by means of fluoroscopy is necessary (Figure 2). The final position of the needle is in the junction between the anterior and middle thirds of the vertebra. Depending on the depth of the catheter, a regular check should be made to see whether any blood, CSF or lymph appears from the needle. If any CSF or lymph is noted, the procedure should be discontinued and a new session can be considered a few days later.
One ml of non-ionic, non-neurotoxic contrast fluid (omnipaque) is
injected. The needle is located in the posterior anterior view just
over the lateral border of the vertebral body. The contrast fluid
should show a sausage-like overlapping image, located between the
thoracic vertebrae and over the lateral border of the vertebrae.
When the needle is located pleurally, the contrast fluid will fan
out.
By injecting bupivacaine 0.5% (5 ml), a diagnostic block will be performed. Higher volumes result in an increased incidence of false positive blocks. This can also lead to additional anaesthesia of the phrenic nerve, which may cause an elevated position of the diaphragm and secondary respiratory problems.
A decision can be made to perform RF treatment during a second treatment session. The needle is positioned at the same location using fluoroscopic monitoring. Once the right location has been verified using tunnel vision and lateral view, the needle position is also checked by electrical stimulation.
The RF generator is connected to the needle and a grounding plate is applied to the patient. The impedance should be lower than 250 Ohm. The patient will feel a vibrating sensation in epigastria at 50 Hz and a threshold of less than 1 V. If the effect of the electrical current is observed in the intercostal area, the needle should be moved further ventrally. In addition, motor stimulation is applied at 2 Hz, focusing mainly on intercostal stimulation. Normally, no stimulation is felt.
When the test results are positive, local anaesthetic is administered (2-3 ml lidocaine 2% or bupivacaine 0.5%). RF treatment can be carried out several minutes later. The needle position is monitored in the lateral view. For each level, the treatment consists of three times 90 seconds at 80°C. Since the most extensive area possible should be treated, the needle is first turned with its curve in a cranial, then in a neutral, and finally in a caudal direction.
Complications
The available data are insufficient to provide satisfactory information on the incidence of complications. No major complications have been reported. Taking the information on neurolytic blocks into account, RF treatment can also induce post-procedural neuritis. This usually disappears within a few weeks and should be treated with medication.
- Hypotension and diarrhoea may occur shortly after the intervention, but are easy to treat.
- As in the case of all procedures at a thoracic level, there is always the possibility of a collapsed lung. Therefore, a control X-thorax should be made within an hour of the procedure. The patient may report a subjective feeling of dyspnoea, which is due to the elevated position of the diaphragm, caused by anaesthesia of the phrenic nerve.
- Thoracic injury is present when a yellowish, turbid fluid is aspired.
- Intradiscal and intravascular injection should always be verified with a contrast fluid.
- Paraesthesia can be felt when the lumbar or thoracic nerve roots are touched.
- Paraplegia is rare, but there have been case reports of alcohol injections damaging Adamkiewicz's arteries.