| Objective:Animal experiment:To provide the theory that ICNF can relieve chest pain and guide the clinical doctors to choose the right freezing time; Clinical study:To observe and evaluate further the effect of relieving pain and clinical significance of ICNF.Methods:1.Animal experiment:28 New Zealand rabbits were randomly divided into 4 groups according to the freezing time diversity, which is 30s group,60s group,90s group and 120s group with every 7 rabbits in each group. CMAP of the 9th intercostal nerve of every rabbit was measured before operation. The 9th intercostal nerve of every rabbit of group was segregated and acted out, which was frozen respectively with cryoprobe of freezing instrument, taking liquid CO2 as the cool air source. The temperature of cryoprobe was-50℃C～-70℃.Freezing time was parted for 30s,60s,90s and 120s according to groups. After the operation completed, CMAP of the 9th intercostal nerve of every rabbit in groups was record, and then compared with each other between groups by SPSS 12.0 software.2. Clinical study:150 patients aged 22 to 78 years, with an average age of 56.5,who had undergone thoracotomy were divided into two groups.100 cases of frozen group and 50 cases of control group (non-refrigerated). Methods of surgery include esophageal carcinoma resection, cardiac carcinoma resection, lung lobe resection, et al. At the end of operation the root of intercostal nerves, which related to chest incision, top and bottom neighbors of incision, and the tube placement, was exposed and frozen with the Kooland-320 treatment.The source of air conditioning was liquid CO2, freezing temperature of -50℃～-70℃, with duration of 90s. Postoperative pain was recorded by visual analogue scales (VAS),including recording the dosage of Morphine needed, The average hospital stay.The data can be compared with each other between groups by SPSS 12.0 software.Results:1. Animal experiment:(1) The CMAP of every rabbit's intercostal nerve before freezing:When the 9th intercostal nerve was stimulated to a certain current, the contraction of the intercostal muscles can be induced. The stimulation current strength remained in 18.6-28.6mA because of individual differences. And the stimulation frequency was 1 times per second. The waveform, latency and area under amplitude of CMAP can be recorded by Evoked Potential/EMG measuring system (MEB-9200K). The average of latency and area under amplitude are 5.17±0.75ms and 8.37±0.55mv. (2) The CMAP changes of the 9th intercostal nerve in different time point after being freezing in 30s group:The waveform disappeared at once and the first day, which couldn't be induced when the amperage and frequency of stimulation were increased. The CMAP of intercostal nerve could be recorded at the 3rd day. The average latency and area under amplitude were 1.98±0.12ms and 10.14±1.26mv. The CMAP of intercostal nerve recovered gradually with time prolonged after freezing,but not to the normal level within 1 month. (3) The CMAP changes of the 9th intercostal nerve in different time point after being freezing in 60s and 90s groups:The waveform had disappeared within 7 days in both groups, which couldn't be induced when the amperage and frequency of stimulation were increased. The CMAP of intercostal nerve could be recorded at the tenth day. The average latency and area under amplitude were 1.04±0.24ms and 14.11±1.34mv in 60s group and 1.00±0.37ms and 15.52±1.27mv in 90s group. The CMAP of intercostal nerve recovered gradually with time prolonged after freezing, but also not to the normal level within 1 month. (4) The CMAP changes of the 9th intercostal nerve in different time point after being freezing in 120s group:The waveform had disappeared with 10 days, which couldn't be induced when the amperage and frequency of stimulation were increased. The CMAP of intercostal nerve could be recorded at the 15th day. The average latency and area under amplitude were 1.35±0.22ms and 23.19±1.06mv. The CMAP of intercostal nerve recovered gradually with time prolonged after freezing, but not to the normal level within 1 month. (5) The data compared with each other between two groups:There was a significant difference (P<0.05) between 30s group and other groups, the same as 120s group. No significant difference existed between 60s group and 90s group (P>0.05).2. Clinical study:25 cases (25%) got 0 score, grade 1-2 in 58 cases (58%), grade 3-4 in 7 patients (7%), grade 5-6 in 5 cases (5%), grade 7-8 in 3 cases (3%), grade 9-10 in 2 cases (2%) in the treatment group. The overall analgesic efficacy (grade 0-6) was 95%, the average VAS score was 2.56.The rate of totally painless was 25%, a slight pain 58%, while there was no grade 0,1 and 2 cases in the control group.6 cases (12%) got grade 3-4,9 cases(18%)got 5-6,15 cases (30%)got 7-8,20 cases (40%) got 9-10.The analgesic efficiency was 30%, and the average VAS score 7.34. There was a significant difference (P =0.000) between two groups. There was also a significant difference between two groups about the average dosage of morphine used (P=0.000) and the average hospital stay (P=0.037).Conclusions:1.Animal experiment:(1)Certain sustained freezing time is required to achieve the purpose of blocking nerve conduction when ICNF is carried out. The rate of function recovery is different because of freezing time diversity.Correspondingly, the effect of relieving pain is different. (2) The function of intercostal nerve disappears immediately when it is frozen longer than 30s, thereby to achieve relieving pain, which provides the function theory that ICNF can relieve chest pain. (3)The conduction function of intercostal nerve can recover after being frozen no matter the freezing time is 30s,60s, 90s or 120s.However, the longer freezing time is, the slower function recovery is. (4) We have got a satisfactory effect of relieving pain clinically when the freeing time is 90s.But this study shows there is no significant difference between 60s group and 90s group. So 60s is a proper freezing time to choose on the basis of relieving chest pain and nerve functional recovery.2. Clinical study:ICNF is an effective method to relieving chest pain after operation., which is beneficial to recovering of respiratory function and the quality of patient life through reducing the dosage of analgesic drug and shorting the hospital stay. ICNF is worth being extended, which is simple and easy to do, safety and effective.
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