Electro-physiological evidence of intercostal nerve injury after thoracotomy: an experimental study in a sheep model

Abstract

Background: Although intercostal nerve injury is one of the major causes for post-thoracotomy pain, the exact mechanisms are still unclear. We sought to evaluate the electro-physiological changes of intercostal nerve injury after thoracotomy in a sheep model. Methods:Adult sheep underwent thoracotomy in the sixth intercostal space by employing diathermy to superior border of the seventh rib. In two sheep, ribs were then spread using retractor spreading for a distance of 7 cm for 30 minutes. In the third sheep, thoracotomy was followed by harvesting intercostal muscles including the neurovascular bundle adjacent to inferior edge of the sixth rib. Thereafter, ribs were spread in the same way, but with the muscle flap dangled between the blades for intercostal nerve protection (dangling muscle flap technique). The nerve conduction velocity of the intercostal nerve was recorded before and after incision of intercostal muscles, immediately and 30 minutes after retractor placement and 30 minutes after removal of the retractor.Results: In the sheep undergoing conventional thoracotomy, the physiological conductivity of intercostal nerve was completely blocked immediately after retractor placement using the same stimulation intensity or even the supra-threshold intensity. The conduction block persisted for 30 minutes during the retractor placement and further 30 minutes after removal of the retractor. In contrast, intercostal nerve conduction was not impaired throughout the experiment with the dangling muscle flap technique. Conclusions:Our experiment provides electro-physiological evidence for intercostal nerve injury after thoracotomy. The injury is primarily attributed to mechanical compression caused by the rib retractor.

Intramuscular stimulation as a novel alternative method of pain management after thoracic surgery

“…Among the many factors that contribute to postoperative pain from thoracic surgery, we focused on intercostal muscle contraction (16). Intercostal muscles are comprised of short-muscle fibers; and once shortened from surgery, it is difficult to stretch back by itself since it is restricted between narrow ICS which is hard to stretch by exercise, requiring physical therapy and/or medication (17).…”

Predicting Post-operative Pain in Lung Cancer Patients using Pre-operative Peak Alpha Frequency

“…Thoracotomy incisions used to gain access to the thoracic organs in the chest, lead to chronic pain in an estimated 25% to 60% of cases (Bayman and Brennan, 2014; Mesbah et al, 2015; Yeung et al, 2019). Considerable nerve damage is common in thoracotomy, as rib re-tractors used in this operation block conduction of intercostal nerves near to the incision by 50-100% (Rogers et al, 2002; Zhang et al, 2017). Video assisted thoracoscopic surgery (VATS), an alternative to conventional thoracotomy, involves less nerve damage due to smaller incisions and no rib re-traction.…”