Huang C J, Tsai M C, Chen C T, Cheng C R, Wu K H, Wei T T
Department of Anesthesiology, Mackay Memorial Hospital, Taipei, Taiwan.
Can J Anaesth. 1999 Jan;46(1):82-6. doi: 10.1007/BF03012520.
Lidocaine diffuses across endotracheal tube cuffs, which may serve as a reservoir for local anesthetic to assist in the prevention of ETT-induced cough while emerging from general anesthesia. However, the rate of diffusion is slow. Two techniques, alkalization and warming, may increase the proportion of uncharged drug available for diffusion. The purpose of this study is to determine the effectiveness of warming alkalization or warming with alkalization on diffusion.
Four preparations of lidocaine 4% were studied. Group (Gr) L-lidocaine (24 degrees C), Gr WL--warmed lidocaine (38 degrees C), Gr AL--alkalized lidocaine (24 degrees C), Gr WAL--warmed, alkalized lidocaine (38 degrees C). Twenty-four Mallinckrodt 8.0 ID (Mallinckrodt Critical Care Division of Mallinckrodt, Inc., Glens Falls, New York) endotracheal tube cuffs were filled with 6 ml of one of the four preparations. They were then placed in a 20 ml water bath at 38 degrees C and samples were drawn from the water bath at intervals for up to 360 min. The lidocaine concentration in each sample was determined by gas chromatography.
The highest lidocaine concentration was reached in Gr WAL (410.98 +/- 8.53 micrograms.ml-1) after 300 min and then decreased to 376.18 +/- 4.59 micrograms.ml-1 after 360 min. In Gr AL the highest concentration (235.05 +/- 2.99 micrograms.ml-1) was reached after 360 min. Lidocaine concentrations in Gr L and WL after 360 min were 3.19 +/- 1.16 micrograms.ml-1 and 4.32 +/- 2.02 micrograms.ml-1 respectively.
Alkalization with or without warming, but not warming alone, promotes lidocaine diffusion from endotracheal tube cuff.
利多卡因可穿过气管内导管的套囊，套囊可作为局部麻醉药的储存库，有助于预防全身麻醉苏醒时气管内导管引起的咳嗽。然而，其扩散速度较慢。碱化和加温这两种技术可能会增加可供扩散的非离子化药物比例。本研究的目的是确定加温碱化或单纯加温对扩散的有效性。
研究了四种4%利多卡因制剂。L组——利多卡因（24℃），WL组——加温利多卡因（38℃），AL组——碱化利多卡因（24℃），WAL组——加温且碱化的利多卡因（38℃）。将24个 Mallinckrodt 内径8.0（Mallinckrodt 公司重症监护部，纽约州格伦斯福尔斯）的气管内导管套囊分别注入6 ml上述四种制剂中的一种。然后将它们置于38℃的20 ml水浴中，每隔一段时间从水浴中取样，最长持续360分钟。通过气相色谱法测定每个样品中的利多卡因浓度。
WAL组在300分钟后达到最高利多卡因浓度（410.98±8.53微克·毫升⁻¹），360分钟后降至376.18±4.59微克·毫升⁻¹；AL组在360分钟后达到最高浓度（235.05±2.99微克·毫升⁻¹）；L组和WL组在360分钟后的利多卡因浓度分别为3.19±1.16微克·毫升⁻¹和•4.32±2.02微克·毫升⁻¹。
无论是否加温进行碱化均可促进利多卡因从气管内导管套囊中扩散，而单纯加温则无此作用。
