Suprascapular Nerve Blocks Indications
Suprascapular nerve blocks can be performed for shoulder pain of various etiologies. Pain in these joints may be improved by injection of local anesthetic (LA) and steroid at the suprascapular notch.
The suprascapular nerve provides the predominant amount of sensory innervation to the glenohumeral and acromioclavicular joint.
Volumes of LA/steroid as high as 10 cc are used. There are several approaches, but common practice is to have the patient sit or lay prone and palpate the spine of the scapula. A line is drawn along it, after which a second line is drawn at the midpoint bisecting it. The needle is inserted 2 cm above the scapular spine on the bisecting line and directed downward into the suprascapular fossa. Bone should be contacted, the syringe aspirated, then injected.
There is a risk of pneumothorax with improper needle placement (Shanahan et al. 2003).
Intercostal nerve blocks have been used to improve postoperative analgesia as well as treat chronic chest wall pain which may result from thoracotomy, postherpetic neuralgia, chest wall metastasis, and trauma, including rib fracture analgesia.
The intercostal nerves arise from the ventral rami of T1-T11. The intercostal nerves lie just inferior to the intercostal artery and intercostal vein at each space.
The chest wall can be segmentally anesthetized at the corresponding rib for each thoracic dermatome. Three to five cubic centimeters of LA is injected medial to the posterior axillary line at the inferior border of the rib to cover all three intercostal branches (Fig. 13.8). If the patient is thin, the ribs may be palpated and the procedure completed without fluoroscopy. The needle is advanced to contact the rib and then directed caudally just past the plane of the rib. Aspiration for air and blood is necessary as the needle is next to the neurovascular bundle and above the lung. The local anesthetic is absorbed into circulation very rapidly and provides the largest systemic absorption of any block in the body, and the addition of epinephrine helps prolong the block and decrease the systemic concentration (Fig. 13.9).
Intercostal Nerve Block
Thoracic Nerve Radiofrequency Lesioning Technique
The junction of the posterior axillary line and the rib to be blocked is identified. A 22-gauge 54-mm radiofrequency needle usually equipped with a 4 mm active tip is advanced aiming for the middle of the rib. After encountering the bone the needle is walked off the inferior border of the rib and advanced about 2 mm deeper to be close to the costal groove. First a trial sensory stimulation with 2 V at 50 Hz is performed to ensure that there is a paresthesia along the distribution of the intercostal nerve to be lesioned. A pulsed radiofrequency lesion is then performed by heating at 40-45° for 5 min or alternatively by heating at 49-60° for 90 s.
Obvious potential complication includes pneumothorax, though data indicate that this is a relatively rare occurrence. It is typically reported at less than 1% with significant pneumothorax reported at approximately 0.1%.
This block is useful for the management of pain in the upper abdominal wall, the chest wall, and the thoracic spine. It is used to control acute pain in conditions such as rib fractures, acute herpes zoster of the thoracic cage, and cancer pain.
The paravertebral nerves exit the intervertebral foramina beneath the transverse process of the vertebrae. The thoracic paravertebral nerve has connections with the thoracic sympathetic chain via the preganglionic white rami communicantes which are myelinated and the unmyelinated gray postganglionic communicantes. Pre- and postganglionic fibers synapse at the level of the thoracic sympathetic ganglia. Sympathetic innervation to the sweat glands, pilomotor muscles of the skin, and the vasculature is by the postganglionic fibers which return to the respective somatic nerves via the gray rami communicantes. The thoracic sympathetic postganglionic fibers also extend over to the cardiac plexus and course up and down the sympathetic trunk, terminating in distant ganglia.
The thoracic paravertebral nerve gives off a recurrent branch to innervate the spinal ligaments, meninges, and respective vertebra. The thoracic paravertebral nerve then divides into an anterior and a posterior branch. The anterior branches go in the inferior aspect of the ribs to become the intercostal nerves which innervate the parietal pleura and the parietal peritoneum. The posterior branch of the paravertebral nerve innervates the facet joint and soft tissues of the back.
The block is performed with the patient in the prone position. The spinous process of the vertebra above the nerve to be blocked is identified (Fig. 13.10). A 3.5-in. needle is used for the block and is inserted after appropriate antiseptic treatment of the skin immediately below and 1.5 in. lateral to the spinous process. The transverse process should be encountered at a depth approximately 1.5 in. at which point the needle is walked off the inferior aspect of the transverse process and inserted another 0.75 in. deeper until a paresthesia is obtained. After negative aspiration for blood or CSF a total of 5 cc of 1% preservative-free lidocaine solution is injected for pain relief. If there is an inflammatory component then 40 mg of methylprednisolone can be added for the initial block.
Thoracic sympathetic ganglion block is utilized when a sympathetic mediated pain syndrome involving the thoracic ganglion is suspected. It can be diagnostic and therapeutic.
With the patient in a prone position, the spinous process of the vertebra just above the nerve to be blocked is identified by palpation. With aseptic technique a 22-gauge 3.5-in. needle is inserted just below and 1.5 in. lateral to the spinous process. The needle is advanced to encounter the transverse process which usually occurs at approximately 1.5 in. after which the needle is walked off the inferior margin of the transverse process to a depth of 1 in. At
this point it is possible to encounter the corresponding thoracic paravertebral somatic nerve which is close to the thoracic sympathetic ganglion. If there is a paresthesia, it is necessary to withdraw the needle and redirect the needle in a more cephalad fashion, keeping close to the vertebral body to avoid a pneumothorax. Once the needle is in the correct position and after negative aspiration for blood and CSF, 1% lidocaine (up to a total of 5 cc) is usually given.
Proper technique will reduce the likelihood of pneumothorax and negative aspiration the likelihood of intravascular injection.
This block can be used for the control of pain after thoracotomy, cancer pain, malignant lesions of the liver and lung, postherpetic neuralgia, and fractures of the ribs. A catheter can be tunneled into the intrapleural space to provide continuous medications to the area. Neurolytic agents can also be administered into the space to relieve intractable pain due to malignancy.
The pleural cavity is the cavity which surrounds the lungs. The region between the pleural sacs is called the mediastinum. The pleura is one of the three serous membranes in the body. From the apex of the lung to the pleura, there are many structures that collectively are described as intrapleural. Pain related to irritation of the lower part of the costal pleura will be referred along its nerve distribution. The visceral pleura, however, is innervated by sensory autonomic nerves. Successful intrapleural blockade most likely involves both intercostal and visceral drug distribution.
Sympathetic nerves as well as somatic nerves can be blocked by pooling of local anesthetic into the interpleural gutter next to the thoracic spine. The position of the patient determines, to a great extent, the types of nerves that can be blocked. For the treatment of sympathetically mediated pain the affected side should be up, whereas placing the affected side down will block the thoracic somatic nerves, the thoracic sympathetic chain, and the intercostal and the thoracic spinal nerves. The eighth rib is first identified on the affected side. At a point 10 cm from the origin of the rib an 18-gauge 3.5-in. styletted needle is inserted in a sterile fashion until the rib bone is encountered. The needle is then walked off the superior margin of the rib, the stylet is removed, and the needle is connected to a 5-cc syringe with air. The pleural space is identified by the loss of resistance to air technique. A pleural catheter is then advanced 68 cm into the cavity, and 20-30 cc of local anesthetic solution is introduced in incremental doses (Fig. 13.11). In the presence of inflammation, 80 mg of methylprednisolone can be added to the local anesthetic with the initial block and 40 mg of methylprednisolone can be added with subsequent blocks.
Again, pneumothorax, though not typical, can occur.
Myofascial trigger points are tender points in muscle thought to originate from tissue trauma. They may cause pain and a resultant decreased range of motion. The trigger points may be located by palpation of a small lump or cord in the muscle by the examiner in concordance with discomfort by the patient. There is a very long list of etiologies of myofascial trigger points.
A myofascial trigger point, also known as a central trigger point, is a hyperirritable foci in skeletal muscle. It is associated with hypersensitive palpable nodule in a taut band. The region is tender and painful to palpation. Widespread, generalized pain and tenderness, as compared with one distinct myofascial trigger point, are often part of a constellation of findings in fibromyalgia. Controversy exists whether this represents a unique syndrome or is a continuum of other pain processes.
Insertion of a needle into the trigger point may elicit a local twitch response (LTR) which confirms the injection site. Trigger point injections are usually performed in a regular examination room. Patients are positioned in a manner to facilitate access to the trigger points as well as minimize potential patient movement. After marking the injection sites, the area should be prepped with cleansing solution. Local anesthetic with or without steroid is then drawn into a sterile control syringe for injection. Under sterile technique the trigger point is fixed with one hand and the other guides the syringe. Several cubic centimeters ofmedication may be injected and should elicit discomfort in the patient's usual area of pain.
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