Pneumothorax After Paravertebral Block and Radiofrequency

Fig. 20.1

Anteroposterior radiographic image showing left apical, 5 mm pneumothorax (Image from personal library)

Repeat chest radiograph 2.5 h later confirmed persistent, unchanged, left apical pneumothorax. At this time, the patient denied dyspnea. Oxygen saturation on room air was in the high 90s despite persistent pleuritic chest pain. She was discharged home and advised to return to the emergency department if symptoms worsened. She reported no symptoms on follow-up telephone call the next day.

One month later, the patient returned to the pain clinic. She felt relief from pain after the left-sided T5 paravertebral radiofrequency ablation. She still experienced pain at the upper portion of the breast above the nipple at the T3 level. She underwent T3 pulsed radiofrequency ablation and once again suffered pleuritic chest pain and dyspnea, even though she remained hemodynamically stable without hypoxia. Chest radiograph revealed a 4 mm apical pneumothorax, and the patient was advised to return to the hospital if symptoms worsened. She was asymptomatic on follow-up telephone calls.

Upon follow-up visit, the patient reported that the radiofrequency ablation was successful but only for several weeks. Her pain was severe and uncontrolled until initiation of transdermal buprenorphine therapy and intermittent, low-dose ketamine infusions. Her pain remains 90% relieved with this ongoing regimen. Coccydynia has not yet recurred. The decision was made not to proceed with additional paravertebral procedures because of the previous two pneumothoraces.

20.2 Case Discussion

20.2.1 Chronic Chest Wall Pain

20.2.1.1 Incidence

Fifty million people in the United States suffer from chronic pain, the direct and indirect cost of which is estimated at 80–100 billion dollars [1]. Drug therapy is inadequate for treating pain in 43% of these patients [2]. When traditional analgesic techniques are unsuccessful, interventional therapies may provide pain relief. More than 200,000 women are diagnosed with breast cancer in the United States every year, and 41% undergo surgery as part of their treatment [3]. Currently, 2.5 million women are breast cancer survivors in the United States alone. The most distressing complaint of surgically treated breast cancer survivors remains to be persistent postmastectomy pain . The estimated incidence of chronic pain after breast surgery (lumpectomy or mastectomy) is 20–30% [3, 4]. In one study, one-third of patients reported persistent postmastectomy pain on the chest wall, arm, axilla, or breast, unaffected since the surgery [3]. Chronic postsurgical chest wall pain is common after thoracic surgery as well. The incidence is 30–40% after thoracotomy, compared with 10% after other surgeries such as inguinal hernia repair or cesarean section [5, 16]. These patients experience a decrease in physical function and quality of life [6].

20.2.1.2 Pathophysiology of Post-resection Chest Wall Pain

The thoracic wall and parietal pleura are innervated by branches of the intercostal nerves originating from the anterior primary rami of T1–T12 and passing through the intervertebral foramina [7]. Surgical trauma and nerve injury modulate pain pathways with permanent synaptic neuronal changes. This neuronal plasticity is often responsible for chronic pain after surgery. Neural blockade interrupts the connection between the site of nerve trauma and the central nervous system (CNS) [8]. Denervation injury can induce neuronal dysfunction and hyperexcitation via central sensitization, disinhibition, and glial cell activation. Compounded by the possible nociceptive barrage from peripheral neuromata at the previous surgical site, the pain from mastectomy may not merely be in the chest wall itself but grossly perpetuated centrally into a debilitating, emotional experience for the patient and their family.

20.2.1.3 Treatment

Various interventional procedures target chest wall pain: thoracic paravertebral steroid injection, neuroma injection, intercostal nerve steroid injection, thoracic epidural steroid injection, dorsal root ganglion ablation, intercostal nerve neurolysis, dorsal column stimulation, and intrathecal drug delivery via implantable pump. Paravertebral block, neurolysis, and radiofrequency ablation are described below.

Paravertebral Block

A paravertebral block provides unilateral sensory and motor blockade, reduces acute postoperative pain and opioid consumption, and may reduce chronic postmastectomy chest wall pain. In a meta-analysis of 89 patients who had breast cancer surgery, paravertebral block reduced chronic pain symptoms (versus conventional analgesia) with an odds ratio of 0.37 at 6 months follow-up. Paravertebral block may decrease the risk of developing chronic pain in one in five women undergoing breast cancer surgery [8]. With paravertebral blockade, there was less motion-related and at-rest pain 12 months postoperatively [9].

Complications from paravertebral blocks are rare: a 0.5% incidence of pneumothorax, 3.8% incidence of vascular puncture, and 4.6% incidence of hypotension. In one study of 1000 paravertebral blocks, two seizures but no pneumothoraces were reported [2]. While paravertebral blockade may prevent chronic chest wall pain, the role of the block has yet to be established for chronic chest wall pain. A low-volume injection provides diagnostic information for a potential ablative therapy at the chest wall. It is thought that a steroid injectate reduces the excitability of the primary afferent neuron and its cell body in the dorsal root ganglion. More peripheral blockade via serratus anterior plane block may relieve chronic post-thoracotomy pain.

Neurolysis

Neurolytics for intractable chest wall pain from cancer are injected with the goal of destroying nerves to interrupt pain pathways. Chemical neurodestructive techniques use alcohol and phenol (carbolic acid and hydroxybenzene). Because alcohol neurolysis produces severe pain on injection, the patient is sedated during the procedure. Physical neurodestructive techniques include cryotherapy, thermocoagulation, and radiofrequency [1]. Denervation carries the risk of potential centralization of pain to cortical structures. Thus, chemical neurolysis is typically a palliative procedure.

Phenol Neurolysis

Advanced cancer pain is inadequately controlled in at least 10–15% of patients [10]. Neurolysis with phenol can improve analgesia and lessen the need for opioids and improve the quality of life [11].The ideal concentration of phenol for injection has not been established. Administration varies from 3 to 13% phenol in an aqueous solution. In a study of 42 patients with severe nonmalignant chronic pain followed 6 months after 4% phenol neurolysis, good pain relief (visual analog scale <3) was achieved in 83%.

Unfortunately, phenol neurolysis is risky, with possible devastating complications. If the phenol solution diffuses to the paravertebral gutter and through the intervertebral foramina toward the epidural space and cerebrospinal fluid (CSF), persistent paraplegia results [11].One patient underwent intervertebral injection of 10% phenol solution along the inferior border of the ribs. One hour later, the patient complained of bilateral lower extremity weakness and difficulty moving. Although IV methylprednisolone was administered and a neurosurgery consult was obtained immediately, the patient remained paraplegic for 6 months [11].

There are several ways to help mitigate complications associated with phenol neurolysis. If a glycerine-based instead of an aqueous solution is used, toxicity is 50 times lower [11]. A smaller dose of phenol may decrease the risk of paraplegia . Performing the procedure away from the spinal cord (i.e., midaxillary line injection versus paravertebral injection) can decrease risk of its entrance into the CSF [11]. In cancer metastases to the spine, adding volume can increase pressure in the epidural space, leading to symptoms of compressive myelopathy [12].

Radiofrequency Ablation

Pulsed radiofrequency ablation has gained popularity over chemical neurolysis because of fewer debilitating side effects. Its mechanism of action is thought to be the inhibition of excitatory C fibers by repetitive burst stimulation of A-delta fibers, decreased overall evoked synaptic activity, and minor structural changes in nerve tissue [13].

Case series have shown pulsed radiofrequency to be effective in spinal, groin, extremity, and facial pain [13]. In a study of 49 patients with chronic postsurgical thoracic pain, pulsed radiofrequency ablation of the intercostal nerves or dorsal root ganglia was performed. Compared to medical management, at 3 months follow-up, 53.8% with radiofrequency ablation reported 50% or greater pain relief compared to 19.9% of patients managed medically. Only 6.7% of the group with intercostal nerve pulsed radiofrequency reported pain relief greater than 50% [13]. In a case study of three patients with intercostal neuralgia, post-thoracotomy pain syndrome, or postherpetic neuralgia, respectively, ultrasound-guided pulsed radiofrequency therapy was performed at 42 °C for 120 s. Visual analog scale pain scores decreased from 7, 6, and 7 to 2, 0, and 1, respectively, and remained that way throughout the 6-month follow-up [14].

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