动物造模,坐骨神经 z-bio 2021-09-08 456

　　Introduction: Peripheral nerve block is often used for postoperative pain and surgical anesthesia. The long-acting local anesthetic itself can also provide 9-14 hours of analgesia. If the block is performed in the morning and afternoon, the patient will usually report postoperative pain at night. The use of opioids can cause potential airway obstruction, resulting in a decrease in saturation. Ideally, a single peripheral nerve block should provide analgesia on the first night after surgery. In order to cure postoperative pain, many additional local anesthetics are under study. The efficacy of clonidine has been proven in many regional anesthesia techniques. However, the results of long-acting local anesthetics are not satisfactory. In some studies, the addition of clonidine to long-acting anesthetics has not found any beneficial effects. Dexmedetomidine is a selective alpha-adrenergic receptor agonist. A previous study showed that in a rat model of sciatic nerve block, the combination of dexmedetomidine and bupivacaine can prolong the sensory and motor block time. Studies have shown that local anesthetics can cause muscle necrosis; however, because muscles regenerate in a normal way, it is believed that this injury may not be clinically important. The dose of local anesthesia is generally reliable for healthy people; however, patients with subclinical neuropathy diabetes or multiple sclerosis may indeed have neurotoxicity. After clonidine administration, an increase in inflammatory mediators was found. Compared with bupivacaine alone, a study reported that adding dexmedetomidine to bupivacaine within 24 hours can significantly reduce peripheral inflammation. The same study found that the value of peripheral nerve inflammation at 24 hours was higher than that of the bupivacaine saline control group alone. Perineural inflammation values in the group receiving bupivacaine and dexmedetomidine and the group receiving only dexmedetomidine were similar to those in the saline group. As discussed in previous studies, it is believed that the use of dexmedetomidine to reduce peripheral inflammation is due to the reduction of pro-inflammatory products of healing immune cells and the increase of anti-inflammatory cytokines at the wound site. It is very important to determine the functional state of nerves. One of the functional assessment methods for nerve healing or conduction disorders is to perform electrophysiological measurements. Electromyography is a common method for clinical and basic research in the study of functional nerves in vivo and in vitro. It has a wide range of applications in the electrical diagnosis and evaluation of peripheral nerve injury of the sciatic nerve in animal models. A study showed that after the end-to-end repair of the incision nerve, the use of a silicone tube filled with hyaluronic acid can have a positive effect on the incubation period and CMAP, thereby positively affecting axon regeneration. CMAP is a valuable parameter, usually showing the time for nerve regeneration and reneuralization. A study showed that stimulated single fiber electromyography (SSFEMG) is a more sensitive electrophysiological method for detecting neuromuscular block in weak muscles and acute organophosphate poisoning rats. These EMG studies show that the use of EMG methods can show nerve healing and nerve damage. In our study, we used the electromyography method to determine the effect of dexmedetomidine injection on nerve conduction. In order to evaluate the effect of dexmedetomidine on the sciatic nerve in rats, we conducted analgesic, histopathological and electromyographic studies.

　　Method: Inferior spinal nerve injection: After weighing the rat, induce anesthesia with 2.5% isoflurane. In the right decubitus position, anesthesia was maintained with 2.5% isoflurane through a mask. A side incision is made on the hind limb to receive the injection. Separate the superficial fascia and expose the sciatic nerve at the proximal end of the bifurcation. After exposure of the sciatic nerve, group D (n=7) was injected with dexmedetomidine 40μg/kg into the perineural cavity, and group S was injected with normal saline 40μg/kg. 30G PPD syringe for injection. In group E (n=2), only the sciatic nerve was exposed, and then sutured again. Record the injection administration time. In order to determine the location of the nerve sample, in the skin preparation process, use the non-absorbable suture under the skin to mark the biceps femoris fascia corresponding to the injection location. The suture was not placed around the nerve, nor did it touch the nerve. After injection, the incision was sutured. The isoflurane anesthesia was interrupted, and the interruption time of the anesthesia was recorded; the rats were placed in a supine cage. Then, the time for the rat to return to the prone position was recorded as the return to righting reflex (RORR).

　　PAW withdrawal delay (PWL) test: After the rat returns to the prone position, the plantar analgesic device is placed on the sole of the foot and the PWL test is performed. The light source is used as a heater for the analgesic meter. Turn on the light source. After the temperature of the corresponding point of the mouse paw reaches 30°C, wait for 5 minutes and move the mouse paw to the corresponding point. Repeat this step for the left and right paws. The rats with no signs of neurobehavioral abnormalities were kept in light and dark environment for 12 hours from the beginning of the experiment to the end of the experiment (6.00-18.00 h). Before surgery, conduct neurobehavioral monitoring for 1 hour every day for 3 days. After the rats received surgery and injected, PWL measurements were taken every 30 minutes, and then the procedure was performed on the left and right paws. All rats were monitored for 210 minutes of neurobehavior. During this period, the hind limbs were evaluated for movement every 30 minutes. Dyskinesia (motor score=1), normal paw position or no dyskinesia (motor score=0). Once the rat has returned to basic sensory and motor values, it is returned to the cage. Before taking out the nerves of the rats at the injection site, starting from the morning after the injection, PWL measurements were performed on both paws 5 times every morning until the nerves were taken out. The daily PWL value is the average of these measurements.

　　Electrophysiology study: After the rat was anesthetized with 2.5% isoflurane, the tail of the rat resting on the back was fixed on the workbench. The needle electrode is placed in the gastrocnemius muscle, and the sciatic nerve is stimulated 10 times with the electrode at a suitable point near the hip joint. The compound muscle action potentials (CMAP) between the peaks of the left and right sciatic nerves and the distal motor latency were recorded. In electrophysiological studies, an electromyography system is used, and the software program Labchart 7 is used to evaluate the measured values. The same operation was performed before the injection to the sciatic nerve and on the 14th day after the injection to the sciatic nerve, and then samples were taken from the sciatic nerve and the results were compared.

　　Histopathological study: On the 14th day, the rats were anesthetized with isoflurane for the first electrophysiological study. After injection of drugs into the sciatic nerve, the rats were anesthetized with isoflurane again and the electrophysiological study was performed. Open the anterior incision of the right hind limb, locate the marked suture, and collect a 1.5 cm long sciatic nerve sample from the corresponding part. Repeat the same procedure for the left hind limb. The nerve sample was fixed in 2.5% glyceraldehyde for 3 days, and then embedded in a paraffin block to prepare a 5 μm cross section. These samples were stained with eosin and evaluated. Confirmed as follows: inflammation around the sciatic nerve (0=no inflammation, 1=mild edema and/or inflammation in small lesions, 2=moderate edema and/or inflammation in local extensive areas, 3=moderate edema and/or inflammation in diffuse areas, local Nerve damage found) (0=no damage, 1=1-2% damage to axon or myelin sheath, 2=2-5% damage to axon or myelin sheath, 3=over 5%% axon or myelin sheath) damage. After the sciatic nerve was removed, the rats were euthanized by cervical dislocation.

　　Result: Comparing the duration of anesthesia during injection in rats, no statistical significance was found. Comparing the RORR values of rats in each group, it was found that the differences between the groups were statistically significant. When the two groups were compared separately, it was found that the RORR value of group D was statistically significantly different from the other two groups. Compared with the other two groups, the RORR value is longer.

　　D group: The PWL value of the right hind limb of the rat was compared with the basic value. It was found that the PWL value was lower than the basic value at 30 minutes after the administration, and the PWL value was higher than the basic value at 210 minutes. There was no statistically significant difference between the 60, 90, 120, 150 and 180 minute measurements. Comparing the PWL value of the left hind limb of the rat with the baseline value, there was no statistically significant difference in 60, 90, 120, 150, 180, and 210 minutes. Compared with the basic value, the PWL value of the right hind limb of the rat has no statistically significant difference from the basic value on the 1, 8, 9, and 14 days; compared with the basic value, the PWL value at other times is statistically longer. The PWL value of the left hind limb of the rat was compared with the basic value, and it was found that the differences in the measured values on the 4-6 days, 9-12 days, and 14 days were statistically significant, and they were longer than the basic value. None of the rats in group D showed dyskinesia.

　　S group: The PWL value of the right hind limb of the rat was compared with the baseline value. There was no statistically significant difference in 30, 60, 90, 120, 150, 180, and 210 minutes. There was no significant difference between the PWL value of the left hind limb of the rat and the baseline value at 30, 60, 90, 120, 150, 180, and 210 minutes. The PWL value of the right hind limb of the rat was compared with the basic value, and the difference was significant at 4-7 days, 10 days, 11 days and 14 days, and it took a longer time to compare with the basic value. The PWL value of the left hind limb of the rat was compared with the basic value, and the difference was statistically significant on day 3-14, and it was longer than the basic value. No rats in S group had dyskinesias.

　　E group: The PWL value of the right hind limb of the rat was compared with the basic value. There was no statistically significant difference in 30, 60, 90, 120, 150, 180, and 210 minutes. There was no significant difference between the PWL value of the left hind limb of the rat and the baseline value at 30, 60, 90, 120, 150, 180, and 210 minutes. The PWL value of the right hind limb of the rat was compared with the baseline value, and the difference was not statistically significant on day 1-14. The PWL value of the left hind limb of the rat was compared with the baseline value, and the difference was not statistically significant on day 1-14. No rats in group E had dyskinesias. The histopathological comparison of the right sciatic nerve of rats showed that there was no statistically significant difference in inflammation and local nerve injury between the groups. The histopathological comparison of the left sciatic nerve in each group showed that there was no statistically significant difference in inflammation and local nerve damage in each group. Comparing the pathological results of left and right nerve tissues in group D, the differences in inflammation and local nerve damage were not statistically significant. Comparing the histopathological results of the left and right sciatic nerves in the S group, the differences in inflammation and local nerve damage were not statistically significant. Comparing the histopathological results of the left and right sciatic nerves in group E, the differences in inflammation and local nerve damage were not statistically significant. When comparing the CMAP and incubation period before and after injection in group D, S and E, the difference in CMAP value after injection was statistically significant. The difference in latency value was not statistically significant. There was a statistically significant difference in CMAP measurement values after injection in group D and group S. Comparing the CMAP measurement values of S group and E group after injection, the difference between the two groups was not statistically significant. Comparing the pre-injection and incubation period of group D, group S and group E, the difference was not statistically significant. There was a statistically significant difference in the CMAP value of group D before and after injection. There was no statistically significant difference in CMAP values between group S and group E before and after injection.

　　Conclusion: Perisciatic injection of dexmedetomidine in rats prolonged the pwl value by 210 minutes. In rats that received dexmedetomidine injection, the duration of RORR reflex was statistically significantly prolonged. Perineural injection of dexmedetomidine to the sciatic nerve did not lead to increased perineural inflammation or local nerve damage, which was statistically significant; however, on the 14th day after the perinerural injection of dexmedetomidine to the sciatic nerve, the CMAP value was significant reduce.