閉鎖循環麻醉技術有利於麻醉病人在手術中維持良好的皮膚血流量

Closed-circuit Anesthesia Preserves Skin Blood Flow during Surgery

背景：閉鎖循環麻醉技術已經廣泛應用在臨床麻醉，並且認為有利於病人術中心臟血管循環狀態穩定。但是閉鎖循環麻醉如何影響手臂皮膚血流的調節作用能力並不明確。因此，實驗假設認為以活寧為主要麻醉的閉鎖循環麻醉有能力提供麻醉手術中病人皮膚較足夠且完整的血流量。因此，本實驗將比較閉鎖循環麻醉與傳統的高流量麻醉方式進行時，病人皮膚的血流量變化的差異。方法：以二十七個接受腹部探查手術病人為研究對象，其中十三人在手術進行時，接受半閉鎖麻醉，另外十四人接受閉鎖循環麻醉。病人經由誘導麻醉插管之後，以固定百分之二的活寧的吸入濃度，配合每分鐘三千毫升氧氣流量進行高流量洗進十分鐘後，在閉鎖循環麻醉麻 醉組病人，氧氣流量降低至每分鐘兩百五十毫升的流量以維持麻醉；而半閉鎖麻醉組病人的氧氣流量則依然以每分鐘三千毫升氧氣流量進行麻醉維持，麻醉維持與手術刺激進行的過程中，以雷射都卜勒皮膚血液流量計量儀來測定手掌皮膚血液流量的變化。在下刀前十分鐘先行測量皮膚血流量的平均值作為基礎值，並在間隔三十分鐘測得之皮膚血流量變化，連續觀 察兩小時，以比較閉鎖循環麻醉與半閉鎖麻醉之間的差異。以監視系統監視並每五分鐘記錄血壓、心跳、吐氣末二氧化碳變化值。結果：接受閉鎖麻醉方式之病人組之皮膚血流量變化比值明顯比接受半閉鎖循環麻醉高，且具有統計上顯著差異。接受半閉鎖麻醉方式之病人組之心跳與平均動脈壓則明顯比接受閉鎖循環麻醉高，且具有統計上顯著差異。結論：閉鎖循環麻醉比半閉鎖麻醉更易維持較良好的皮膚血液流量，以及穩定的心跳血壓。閉鎖循環麻醉有利於組織微循環血流狀態，提供臨床麻醉新選擇，值得重視與推廣。

Background: Closed-circuit anesthesia (CCA) has been suggested to provide better hemodynamic stability, but the relative contribution of CCA to the control of blood flow in microcirculation is not defined. It is hypothesized that isoflurane-based CCA provides a favorable skin blood flow mediating via lesser circulatory response to surgical stimulation. This study was purposed to compare the effects of isoflurane conveyed by CCA with that by semiclosed anesthesia (SCA) on the preservation of skin blood flow in the forearm. Methods: Twenty seven patients scheduled for colorectal surgery were enrolled for the study and randomly assigned to one of two groups, either receiving CCA (n = 14) or SCA (n = 13). Anesthesia was induced with fentanyl (100 μg) and thiopental (4-5 mg/kg), and intubation was facilitated with pancuronium priming (0.015 mg/kg) and succinylcholine (1.25 mg/kg). Two percent isoflurane in high O2 flow (3 L/min) was given for 10 min to each patient initially to wash isoflurane in the functional residual capacity of both lungs and the breathing circuit. In the CCA group, after insoflurane wash-in the O2 flow was reduced less than 250 mL/min with isoflurane vaporizer setting adjusted to 3-5% to keep inspired isoflurane at 2% for maintenance of anesthesia. In patients of in the SCA group, anesthesia was maintained with isoflurane in 3 L/min O2 flow keeping the inspired isoflurane concentration at 2% throughout the surgery. A laser Doppler flowmetry (Moore instrument, Axminster, England) was used to measure skin blood flow (SBF) at the thenar eminence of left hand. Skin blood flow was determined and was taken as baseline (100%) at the 10th min after tracheal intubation. Thereafter, the magnitude of SBF was determined likewise every 30 minutes over the two-hour study. The hemodynamic and respiratory parameters were measured at every 5 minutes in both groups. Results: In comparison with the SCA group, the CCA group had a greater magnitude of skin blood flow (106 ± 13% vs. 75 ± 17%; 104 ± 14% vs. 68 ± 14% P < 0.01) at the 60th and 120th min. Also, patients who received SCA had higher mean arterial pressure (MABP) (82 ± 8 vs. 78 ± 8; 89 ± 6 vs. 77 ± 10, P < 0.05) and heart rate (HR) (80 ± 9 vs. 73± 9; 82 ± 15 vs. 71 ± 14, P < 0.05) at the 60th and 120th min. Conclusions: Closed circuit technique for isoflurane anesthesia is feasible and advantageous. It not only facilitates favorable skin blood flow but also provides better hemodynamic stability in comparison with semiclosed technique for isoflurane anesthesia.