Experimental And Clinical Study On Freezing Intercostal Nerves For The Relief Of Postoperative Chest Pain

Objective: (1) To explore the pathological change including damage and repair process of nerve in different freezing time at same temperament(-70℃);(2) To make sure the safety of the cryoanalgesia.Materials and methods: Freezing equipment was the K520 Cryosurgery made by beijing Kooland medical Devices Co. Ltd. The freezing temperature was -70℃. In the experiment we separated nerves under the rib, froze intercostals nerves at different time including 30,60, 90, 120, 180 seconds. We got material at the operative day, after 10 days and 60 days Respectively , then carried on the pathology check.Results: We observed on operative day that the freezing nerves with no less than 90 seconds appeared brown print with the naked eye, but the freezing nerves at 30 and 60 seconds have no obvious change. With the microscope , we observed that freezing nerves at 30 and 60 seconds presented a little edema of the neurilemmas , axons and myelin sheaths and the freezing nerves at 90,120 and 180 seconds presented degeneration, necrosis of the nerve fiber. After 10 days, nerves at the freezing time more than 90 seconds became thinner than normal with the naked eye. With the microscope, the performance of nerve at 30 seconds presented degeneration, the performance of nerve at no less than 60 seconds presented more necrosis .We can watch nerve repair at no more than 120 seconds, but nerves repair change was not obvious at 180 seconds. After 60 days, all nerves had no obvious differentiation than normal with naked eye .The basic pathological changes of all nerves became normal With the microscope, but all still hadhyperplasia changes and the nerves at 180 seconds presented fiber alignment a little mess.Conclusions:(l)The damage of nerve progressed along with freezing time from 30seconds to 180seconds at -70°C.(2) The freezing nerve presented early obvious damage at no less than 90 seconds.(3) The more freezing time ,the more time to repair nerves.(4) At - 70°C,the freezing nerves at 180 seconds still can repair. The cryoanalgesia is safe.