Electrodiagnostic evaluation of the effect of compression time and intensity on nerve conduction and nerve recovery time in the peripheral nervous system

Objective: Electrodiagnostic evaluation of the effect of compression time and intensity on nerve conduction and nerve recovery time in the peripheral nervous system. Patients and Methods: Six adult male farm pigs (sus scrofa) were divided into three sub-groups. Sciatic nerve opening was performed under total intravenous anaesthesia. By stimu-lating the sciatic nerve with the bipolar probe, contraction of the muscles was observed. TcMEP responses were measured from electrodes placed on Semimembranosus, Rectus Femoris, Vastus Medialis, Vastus Lateralis, Gastrocemius, Soleus, Semitendinonus muscles. Sciatic nerve compression was applied to reach the target compression value within a max-imum of one minute. In the sciatic nerve TcMEP values, compression was performed in three groups, with 50% in the first group, 70% in the second group, and 90% or more in the third group. The amount of compression was applied as 1, 5 and 8 minutes in each group. After starting in accordance with the study plan, this stage was performed with a single sub-ject, considering that 90% or more falls in MEP caused irreversible damage regardless of time. One of the subjects was included in the 50% compression group. After the termination of each compression application, it was planned to evaluate MEP as 5s-60s-5min-10min-30min-60min. During the study, a break was taken for 15 minutes after 1 minute of com-pression, and half an hour after 5 minutes of compression. Evaluation was terminated in sub-jects with a baseline response. If a basal response was not obtained, the follow-up was com-pleted to 60 minutes. All groups were sacrificed using potassium chloride at the end of the study. Results: Compression group at 50% MEP loss: In this group, 3 pigs and 6 sciatic nerves were studied. The vastus lateralis was the first muscle to be affected in all groups. It took an average of 118 ± 25 (60-130) seconds for all data to return to baseline after one minute of compression. While 50% MEP reduction was observed in the vastus lateralis muscle in four legs, 50% MEP loss was first observed in the soleus muscle in 2 legs. After five minutes of compression, it took an average of 28 ± 8 (20-38) minutes for all data to return to baseline. The first 50% MEP decrease was detected in the vastus lateralis muscle in three legs, while it was detected in the vastus medialis muscle in the other three legs. In eight minutes of compression, the vastus lateralis was affected first. Neuromonitorization was continued for 60 minutes in all pigs after compression. MEP values did not return to baseline in any mus-cle group. Compression group in 70-80% MEP loss: The vastus lateralis was the first muscle to be af-fected in all groups. After one minute of compression, it took an average of 125 ± 45 (60-250) seconds for all data to return to baseline. While 50% MEP reduction was observed in the vastus lateralis muscle in both legs, 50% MEP loss was first observed in the soleus mus-cle in 2 legs. When compared to the group with 50% MEP reduction, the time to return to baseline value after 1 minute of compression was found to be statistically significantly longer in the group with 70-80% MEP reduction (p<0.001). After five minutes of compres-sion, stimulation was continued with 60 minutes of neuromonitoring in all pigs. MEP values did not return to baseline values in any muscle group. In the final evaluation, the mean loss of MEP in vastus lateralis muscle was 55.4% compared to baseline, 41.4% in rectus femoris muscle, 33.2% in vastus medialis muscle, 55.1% in semimembranosus muscle, 42.2% in gastric-nemius muscle, 38.9% in soleus muscle, and 63% in semitendinosus muscle. seen. Compression group in >90% MEP loss: In this group, compression was evaluated by ensur-ing that 2 pigs, 4 sciatic nerves and any lower extremity MEP value decreased by >90% compared to baseline. Considering that >90% decrease in MEP after starting the study plan in accordance with the study plan causes irreversible damage regardless of time, this stage was performed with a single subject. The vastus lateralis on both sides was the first muscle to be affected. While 100% MEP reduction was observed in the vastus lateralis muscle on one leg, 100% MEP loss was first observed in the vastus medialis muscle on the other side. After one minute of compression, neuromonitoring was continued for 60 minutes on both sides. MEP values did not return to baseline values in any muscle group. Conclusion: In conclusion, 50% decrease in the MEP value in the peripheral nerve com-pared to the baseline may be reversible, while compression for 8 minutes or longer causes irreversible perfusion damage in the nerve and basal MEP responses cannot be obtained. 70-80% decrease in the MEP value in the peripheral nerve compared to the basal 1 minute peri-od while it may be reversible for 5 minutes or longer, MEP values cause irreversible perfu-sion damage to the nerve in compression for 5 minutes or longer. A decrease of >90% in peripheral nerve MEP value compared to baseline causes irreversible perfusion damage re-gardless of the duration. It is faster for MEP values to return to baseline. The longer the compression time, the longer the MEP value returns to baseline.