經皮神經阻斷術：決定酚和神經組織接觸的適當作用時間

Percutaneous Nerve Block: Determining the optimal duration of phenol in contact with the nervous tissue

林朝加(Jau-Jia Lin)

指導教授 ： 張權維

國立臺灣大學/醫學院/臨床醫學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01931

摘要

痙攣張力為上運動神經元疾病的典型特徵，是復健進展的顯著不利因素，也是臨床醫師所面對的一項難題。酚神經阻斷術的優點是可以提供較持久及可逆的肌肉張力降低，作用在操作時立即可見，而且價格相當便宜。目前的做法是在電刺激器的導引下，用最小的電流達到最大的肌肉收縮，然後注射藥物直到目視肌肉收縮停止。我們認為在找到神經的位置時，可以將電刺激器關掉，注射定量的藥物，在充分反應若干時間後，再開啟刺激器來決定是否需要更進一步的藥物注射，以降低有效藥物劑量。我們以大白鼠為實驗動物來研究5%酚水溶液和其坐骨神經接觸的適當反應時間，並嘗試建立連續藥物注射和單一藥物注射的比較以及藥物劑量和神經傳導阻斷程度的關係。
研究方法
一、決定單一劑量藥物破壞周邊神經組織所需之作用時間
暴露坐骨神經，將刺激電極放置於神經主幹，記錄電極在腓腸肌肌腹中點，調整刺激參數來取得最大肌肉複合運動動作電位振幅。將黑色套管放置於刺激電極下方的神經上並在末端做封填，注射0.02毫升藥物，記錄肌肉複合運動動作電位振幅下降10%(開始減少), 25%, 50%, 75% 及振幅< 0.1mV(完全消失)所需的時間。
二、瞭解單一藥物注射的劑量和反應關係
在電刺激導引下經皮定位坐骨神經，連續注射藥物直到示波器上肌肉複合運動動作電位振幅完全消失，將八條神經所使用的藥物劑量平均。接著在定位坐骨神經後，關掉電刺激器，分別以上述平均劑量之20%、40%、60%、80%注射，和酚水溶液作用適當時間後，記錄腓腸肌肌肉複合運動動作電位振幅來決定劑量反應關係，最後用開刀暴露及電刺激神經來確認肌肉複合運動動作電位是否依然存在。
結果
(1) 暴露神經接觸酚水溶液，肌肉複合運動動作電位振幅於平均74 (48-90) 秒完全消失，因此將酚作用的適當時間定為90秒，預期所有神經組織都能和藥物充分作用。
(2) 經皮方式連續注射藥物至肌肉複合運動動作電位完全消失所需要的平均劑量為0.8毫升。八條神經使用5%酚水溶液0.16毫升 (20%)，等待90秒後，肌肉複合運動動作電位振幅完全消失。因此將注射劑量向下修正為5%，10%及20%來做比較。使用5%及10%的藥物劑量，在作用90 秒後，只有部份可使腓腸肌肌肉複合運動動作電位完全消失。
結論
連續注射藥物使肌肉停止的方式的確會使用過多劑量的酚水溶液，臨床上可以使用漸進式注射模式，先以小劑量注射，等待藥物適當作用一段時間後，再決定是否需要更進一步注射。此外，本實驗無法建立藥物劑量和相對反應之明確關係。

關鍵字

痙攣張力 ； 酚 ； 神經阻斷術 ； 上運動神經元疾病

並列摘要

Percutaneous phenol block continues to be among the most frequently used local injection methods for reducing spasticity in adults. It can produce a prolonged but not permanent motor block through nonselective axonal degeneration, a mechanism that interrupts components of the stretch reflex arc. Its effects are immediate and dramatic. Although the procedure is relatively easy to perform and low cost, many physicians in the world are reluctant to use it because they think the blocking effects are not easily titrated. The degrees of nerve destruction and the body’s ability to regenerate after damage by phenol block have been poorly evaluated. Many variables can influence the effect of phenol block, including the concentration and volume of phenol injected, the duration of phenol in contact with the nervous tissue, localization techniques, selection of block sites, and application techniques. In the current practice, nerve localization is determined if maximal target muscle contraction by minimal electrical current is achieved by using an electrical stimulator. Five percents of aqueous phenol solution is continuously injected until visible muscle contractions disappear. The optimal duration needed for adequate neural damage by injected phenol has not yet been well understood, and the totally used phenol volume may be significantly larger than actually needed. Larger dose of phenol injection can cause greater nearby tissue damage and make further localization more difficult. In this study, we try to determine the optimal duration of phenol in contact with the nervous tissue in Wistar rat, and investigate the dose-response relationship of 5% aqueous phenol solution in peripheral nerve block.
Materials and Methods
The optimal duration of phenol in contact with the nervous tissue. After surgical exposure of the sciatic nerve, stimulation electrodes were placed on the main trunk and recording electrodes were placed on the midbelly of the gastrocnemius muscle. We adjusted the stimulation parameters to obtain the steady amplitude of compound motor action potential (CMAP) under continuous stimulation. The filter setting was 10 to 100,000Hz. The CMAP of the gastrocnemius muscle were recorded after 8 to 12 supramaximal stimuli (square wave stimulus of 100-μs pulse width) of the sciatic nerve. Peak to peak amplitude was measured in the response of the maximal amplitude. A small trough that held approximately 100 μL of solution was fabricated around the sciatic nerve. The trough was made of a polyethylene tube that was incised longitudinally. It was spread out with a curved mosquito forceps to transform its tubular shape into a flat sheet. Then it was inserted beneath the tibial nerve. When the mosquito forceps were removed, it returned to its original tubular form that then encircled the tibial nerve. The lower end of the trough was packed by wax. 0.02μL of 5% aqueous phenol solution was dropped into the trough, and then recorded the duration for the muscle CMAP amplitude attenuated by 10%( start to decline), 25%, 50%, 75% and less than 0.1 mV.
Dose-response relationship. Sciatic nerves were located percutaneously under guidance by the electrical stimulation. After maximal muscle contraction was achieved by using minimal electrical current, a 27 G Teflon-coated needle（BOTOX Injection Needle, Allergan）was used to inject phenol solution continuously until the muscle CMAP amplitude disappeared on the monitor. The injected volume of 8 samples was averaged. Twenty percent, 40%, 60% and 80% of the above averaged volume of 5% phenol solution was injected percutaneously at a rapid rate after electrical localization of the sciatic nerves. Then the electrical stimulation was turned off immediately. After the adequate duration which was determined by the previous experiment, the electrical stimulator was turned on and continuously recorded CMAP amplitude of the gastrocnemius muscle to determine the dose-response relationship. Finally, surgical exposure of the sciatic nerve was made and observed if the muscle CMAP amplitude still presented with electrical stimulation.
Result
After phenol in contact with the exposed sciatic nerve, the muscle CMAP
amplitude disappeared at an average duration of 74 seconds (range: 48 to 90). So the
optimal duration for complete phenol effect was set as 90 seconds. After this period of time, full reaction with phenol at all the tested nerves could be expected. The average injected volume of phenol solution to achieve complete absence of the muscle CMAP amplitude by percutaneously continuous injection was 0.8 μL. Ninety seconds after injecting 0.16 μL (20%) of 5% aqueous phenol solution rapidly, the muscle CMAP amplitudes were totally absent in 8 tested sciatic nerves. So the injected volume was adjusted to 5%, 10% and 20% of the average volume which was 0.8μL for comparison. Using 5% or 10% of the average volume, complete absence of the CMAP amplitude was only seen in some tested nerves after the duration of 90 seconds.
Conclusion
The continuous injection model for percutaneous phenol block indeed uses significantly more phenol than actually needed. Clinically, we suggest progressive injection model which inject small amount initially, and determine if there are any need for further injection after drug effects for an optimal duration. This study can not show the dose-response relationship clearly, however, dose-dependent effect is evident before the threshold volume is given.

並列關鍵字

spasticity ； phenol ； nerve block ； upper motor neuron disease

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