Utility and safety of low-concentration nitrous oxide anesthesia in ptosis surgery

To evaluate the utility of low-concentration nitrous oxide (N(2)O) anesthesia in ptosis surgery This study was a retrospective consecutive case series that included 54 successive patients with blepharoptosis who underwent bilateral levator aponeurosis advancement and on whom skin resection performed by the same surgeon between August 2016 and July 2017. Among these patients, 27 were operated with a local anesthesia injection (air group) and 27 with a local anesthesia injection and low-concentration N(2)O anesthesia (N(2)O group). All N(2)O cases used a total of 6 L of gas comprising 70% oxygen and 30% N(2)O. Preoperative and postoperative blood pressure (BP) and heart rate (HR) and intraoperative pain, anxiety, nausea, and memory were measured immediately after surgery using visual analog scale score (VASS). Additionally, perioperative side effects were examined. There was no significant difference in age, sex, and preoperative and postoperative margin reflex distance (MRD) between the 2 groups (all P > .05). The intraoperative mean peripheral oxygen saturation was significantly higher (97.5% ± 1.6% vs 99.5% ± .6%, P < .001), intraoperative HR was significantly lower (78.2 ± 12.8 vs 70.7 ± 11.6 bpm, P = .02), and operation time was significantly shorter (33.1 ± 8.1 vs 29.4 ± 10.3 minutes, P = .03) in the N(2)O group than in the air group. Difference between intraoperative and preoperative systolic BP (BPs) (+15.8 ± 18.0 vs + 3.1 ± 21.7 mm Hg, P = .02), diastolic BP (BPd) (+7.0 ± 17.4 vs −2.3 ± 13.6 mm Hg, P = .04), and HR (3.2 ± 8.5 vs −3.9 ± 9.4 bpm, P = .01) was significantly lower in the N(2)O group than in the air group. VASS of intraoperative pain was significantly lower in the N(2)O group than in the air group (49.5 ± 24.7 vs 22.6 ± 14.9, P < .001), whereas intraoperative anxiety and memory did not present significant differences between the groups (P = .09 and P = .45, respectively). Intraoperative nausea score was 0 for all cases in both groups. There was no other side effect. Ptosis surgery with anesthesia using 30% N(2)O may effectively suppress intraoperative BP and HR along with pain and shorten the operation time without side effects such as nausea.