Surgical Strategy and Treatment for the Prevalence of the Post- Thoracotomy Pain Syndrome

The various types of pain evoked after thoracic surgery are wound pain, pulmonary apex pain due to the drain, pain caused by intercostal nerve damage, visceral pain due to manipulation of the pleura/bronchi during surgery. As the dominant nerve differs among painful areas, the innervation regions requiring analgesia are extensive, causing difficulty in pain control. These pains are treated by the thoracic epidural anesthesia, the administration of anti-inflammatory analgesics such as nonsteroidal anti-inflammatory drugs, gabapentin (anti-epileptic drug) as a central nerve system drug, or tranquilizers. When nociceptive input into the central nerve system with acute, intense postoperative pain is sustained, a change to chronic pain such as postthoracotomy pain syndrome (PTPS) can occur [1]. PTPS is defined by the International Association for the Study of Pain as neuropathic pain with dysethesia that is burning and stabbing, and persists for at least two months following the surgical procedure. Its incidence is 80% at 3 months, 75% at 6 months, and 61% at 1 year after surgery; the incidence of severe pain is 3-5%. PTPS interferes with daily life in 50% of patients [2]. The incidence of PTPS is similar between thoracoscopic surgery and thoracotomy [3-5], and the causes of PTPS include rib fracture, intercostal nerve injury due to compression by the rib retractor, and rib hyperextension. An anxious personality of patients was also reported to tend to be positively correlated with the incidence of PTPS [6]. In thoracic surgery, there are differences in the incision size among surgical techniques and surgical invasiveness to the chest wall among approaches to the thoracic cavity, such as posterolateral thoracotomy, axillary thoracotomy, median sternotomy, a median incision, a small incision, and conventional video-assisted thoracic surgery (c-VATS) with only a trocar used in VATS. It is self-evident that the intensity and the fear of postoperative pain also differs among patients. When postoperative wound pain is compared between cVATS using only the trocar and thoracotomy involving rib resection with a large wound, the degree of surgical invasiveness to the chest wall is often inconsistent with the pain intensity, which supports the above individual differences. Even when thoracotomy is performed after the intercostal bundle is treated as minimally as possible, or even when cVATS is performed, some patients occasionally develop marked symptoms of neuropathic pain such as burning, shooting, and tingling sensations and hypesthesia in the area from the precordial region at the intercostal thoracotomy level to the upper abdominal region. Their stress is marked when these symptoms develop. Actually, in patients with PTPS, sensory abnormalities such as allodynia (pain induced by normally innocuous, weak stimuli) and hypesthesia sometimes persist around the thoracotomy wound or the anterior axillary line area or upper abdominal area at the thoracotomy intercostal level for a long period after surgery. Since no drugs have been developed to alleviate these symptoms, pain causing discomfort whenever clothes come into contact with the area around the wound may reduce patients’ activities of daily living and delay their return to society.