以極低劑量Tetracaine脊椎麻醉進行直腸肛門手術

Minimal Dosage of Tetracaine Supplemented with Epinephrine for Spinal Anesthesia in Anorectal Surgery

背景：脊椎麻醉由於施行方便成本低廉，目前廣泛地被用於下半身手術；雖經長時間大量的經驗及研究，但它仍有相當多的報告顯示，低血壓及心率過緩仍是相對常見的副作用。尤其嚴重心率過緩或心跳停止，由於難以預估其發生時機及機制更是麻醉醫師的夢魘。降低劑量對低位及短時間手術應有探討價值。本研究即測試降低劑量對於直腸肛門手術之可行性。方法：本研究以30位進行直腸肛門手術患者進行研究，比較以3.0或6.0毫克tetracaine混合0.1毫克腎上腺素實施脊椎麻醉，對病患之影響。30位患者隨機分成兩組每組15人，除了tetracaine劑量不同外，其他操作均一樣。藥品注射完後，即以磨鈍之18號針測試觀察，並每分鐘記錄患者皮節阻斷的範圍共10分鐘；期間每3分鐘記錄心跳及血壓。然後翻成俯臥姿勢進行手術，其後並每5分鐘記錄心跳及血壓。數字資料以Student-t，非數字資料則以chi-square進行統計分析。P值小於0.05代表明顯差異。結果：兩組在10分鐘時皮節阻斷範圍，統計上有明顯差異(P <0.05,T9 vs. T12)。心跳及血壓兩組間並無明顯統計上差異；但發生低血壓病患數部分則在6.0毫克組有較高的趨勢(6.7 vs.26.7％；P= 0.08)，心率過緩之發生率則兩組一致。結論：降低tetracaine之劑量由6.0至3.0毫克，混合0.1毫克腎上腺素實施脊椎麻醉，可提供直腸肛門手術足夠皮節阻斷範圍；降低劑量或可降低低血壓之機率，但無法降低心率過緩之發生。

Background: Spinal anesthesia has been widely used in clinical setting with relatively high incidences of hypotension and bradycardia. Lowering the dosage of local anesthetics is one of the methods to mitigate the side effects. This study was to evaluate the feasibility of lowering the dosage of tetracaine in spinal anesthesia for patients undergoing anorectal surgery. Methods: Thirty patients scheduled for anorectal surgery were studied. Patients were randomly divided into experiment (n = 15, 3.0 mg of tetracaine) and control groups (n = 15, 6.0 mg of tetracaine). The extent of analgesia was assessed by loss-of-sensation to pinprick. Dermatomic level of the sensory block was evaluated and recorded every minute for 10 minutes. BP and HR were recorded at 3-min interval for the 10-min in the study period. Numeric data were statistically analyzed with Student's t-test. The categorical data were compared using the chi-square test. P-value less than 0.05 was considered statistically significant. Results: Ten min after the injection, the mean peak level of sensory block reached T12 for experiment and T9 for control groups. A noticeable difference in frequency of hypotension between two groups was found though it was not statistically significant (P = 0.08). Incidences of moderate bradycardia and severe bradycardia were similar in both groups, being 13.3% and 6.7% respectively. Conclusions: This study confirmed that lowering the dosage of tetracaine to 3.0 mg could equally provide adequate spinal anesthesia for anorectal surgery. The reduced dosage has the tendency of reducing the rate of hypotension, but apparently it does not reduce the incidence of bradycardia.