Nitrous oxide anxiolysis for elective cesarean section

STUDY OBJECTIVE: To determine if inhaled 40% nitrous oxide (N(2)O) via facemask is an effective anxiolytic in women undergoing elective cesarean section under spinal anesthesia. STUDY DESIGN: Prospective, randomized, double-blinded study. SETTING: Tertiary-care women's hospital. PATIENTS: Sixty American Society of Anesthesiologists physical status I and II patients scheduled for elective cesarean section under spinal anesthesia. INTERVENTIONS: Patients were randomized to 2 groups to receive either 100% O2 via facemask or 40% N2O in O2 via facemask. MEASUREMENTS: Vital signs (blood pressure, heart rate, and oxygen saturation) and measured variables (visual analog scale [VAS] anxiety, VAS pain, and sedation scores) were obtained at specific periods during the procedure (preoperatively, entering the operating room, spinal injection, skin incision, uterine incision, delivery, and at the conclusion of the surgical procedure). In addition, surgical time and delivery time, mean dose and percentage of patients requiring ephedrine or phenylephrine boluses, the emesis rate, and Apgar scores were measured. MAIN RESULTS: No differences were noted with respect to maternal mean blood pressure, heart rate, pulse-oximeter oxygen saturation, and sedation or VAS pain scores during the measured periods. No differences were noted in surgical and delivery times, mean dose, or percentage of patients who required ephedrine or phenylephrine to maintain maternal blood pressure, the emesis rate, or 1- and 5-minute Apgar scores. Mean anxiety scores for the N2O group were significantly lower at the time of spinal injection, skin incision, and uterine incision. Multivariate analysis of variance for high-anxiety patients (> or =50 VAS) revealed significantly lower VAS scores in the N2O group, compared with the O2 group again at spinal injection, skin incision, and uterine incision. CONCLUSIONS: Inhaled 40% N2O via facemask provides effective anxiolysis in women undergoing elective cesarean section under spinal anesthesia in patients with high anxiety (> or =50 VAS) at the time of spinal injection, skin incision, and uterine incision.