engleski

Nitrous oxide added at the end of isoflurane anesthesia hastens early recovery without increasing risk for PONV

Introduction: Nitrous oxide (N2O) increases risk for postoperative nausea and vomiting (PONV).(1) This effect appears to be dose/depended.(2) To minimize risk of using N2O some anesthesiologists use N2O at the end of volatile anesthetic anesthesia. We investigated if adding N2O at the end of isoflurane anesthesia had influence on extubation and PONV. Materials and Methods After obtaining IRB approval and informed consents, 64 women, ASA PS I-III, scheduled for laparoscopic assisted vaginal hysterectomy were randomized into two groups according to carrier gas: G0 – air in 30% oxygen (n=32) and G1 – the same mixture until last 30 minutes of surgery when 70% nitrous oxide and 30% oxygen was used (n=32). No PONV prophylaxis was given. Anesthesia was induced with thiopental 5 mg/kg, vecuronium 0.1 mg/kg and fentanyl 1-2 μg/kg IV, followed by 10mL/kg saline and maintained with isoflurane ~ 1MAC. Early recovery (time to extubation, eye opening, following commands, orientation) was measured by a blinded anesthesiologist. PONV and pain scores were measured at 2 h and 24 hours postoperatively. Diclofenac and meperidine was used for pain and metoclopramide for PONV. Data were analyzed using Chi-Square and Mann-Whitney test. P<0.05 was considered significant. Results Average mean time of nitrous oxide administration in G1 group was 26.2 ±10.4 in minutes. There were no significant differences between two groups for age, BMI, h/o smoking, h/o motion sickness and/or PONV, duration of anesthesia and surgery. The times to extubation and eyes opening were significantly less for G1 than G0 group while differences inability to follow commands and orientation did not reach statistical significance. The incidence of PONV, rescue antiemetic usage, maximal nausea VAS score, pain VAS score at 24 hours and perioperative opioid consumption were not different between groups.(Table 1) Discussion: Adding N2O at the end of the isoflurane anesthesia hastened extubation for 2 minutes, eyes opening for 3.5 minutes and orientation for almost 4 minutes after laparoscopic assisted gynecologic surgery. N2O may be added in last 20-30 minutes of isoflurane anesthesia without increasing risk of PONV. References: 1.Myers et al. ENIGMA trial. Anesthesiology 2007 ; 107:221–31 2. Mraovic et al. Anesth Analg 2008 ; 107:818-23 Table 1. Recovery times and PONV data. G0 (n=32) (air) G1 (n=32) (air + N2O at the end) P Tracheal extubation (sec)ª 431.5 (124-968) 296.0 (85-842) 0.037* Open eyes (sec)ª 780.0 (255-1725) 567.5 (180-1508) 0.014* Follows orders (sec)ª 903.0 (272-1745) 657.5 (240-1722) 0.061 Orientation (sec)ª 997.5 (284-1909) 770.0 (280-2290) 0.050 PONV (24h)(n, %) 25 (78%) 21 (66%) 0.266 PONV (0-2h)(n, %) 23 (72%) 16 (50%) 0.073 PONV (2-24h )(n, %) 11 (34%) 13 (41%) 0.606 Metoclopramide (n%) 20 (63%) 13 (41%) 0.080 ª Data presented as median and range (min–max). *P<0.05

nitrous oxide; early recovery; PONV

doi:10.1213/01.ANE.0000398215.59935.49