Effect of nitrous oxide on propofol requirement during target-controlled infusion for oocyte retrieval

• Published in: International journal of obstetric anesthesia 2007-01, Vol.16 (1), p.13-16
• Main Authors: Handa-Tsutsui, F, Kodaka, M
• Format: Article
• Language: English
• Subjects: Adult; Ambulatory Surgical Procedures; Anesthesia & Perioperative Care; Anesthesia, Intravenous - methods; Anesthetics, Inhalation - pharmacology; Anesthetics, Intravenous - administration & dosage; Dose-Response Relationship, Drug; Female; Fertilization in Vitro; Humans; In-vitro fertilization; Monitoring, Intraoperative; Movement - drug effects; Nitrous Oxide - pharmacology; Obstetrics and Gynecology; Oocytes; Propofol; Propofol - administration & dosage; Regression Analysis; Target-controlled infusion; Tissue and Organ Harvesting; Ultrasonography, Interventional - methods
• ISSN: 0959-289X; 1532-3374
• DOI: 10.1016/j.ijoa.2006.08.001

Background Oocyte (egg) retrieval for in-vitro fertilization is a relatively short procedure, usually performed as an outpatient. Propofol is a suitable anesthetic agent. Target-controlled infusion is a recently developed system that aids rapid recovery from propofol anesthesia. This study sought to determine the target concentration of propofol required to prevent movement in 50% (Cp50) and 95% (Cp95) of women during oocyte retrieval, and investigated whether supplemental nitrous oxide (N2 O) modified the Cp50 and Cp95. Methods Forty-seven women scheduled for oocyte retrieval were randomly selected to receive either O2 -air mixture (control group; n = 23) or 50% O2 -N2 O mixture (Nitrous oxide group; n = 24). Propofol was infused using a target-controlled infusion system with the concentration determined by up-down sequential allocation using 0.5 μg/mL step size. Transvaginal oocyte retrieval was performed after reaching target blood concentration. Patient responses to oocyte retrieval were noted as either no movement or movement. Results Using target-controlled infusion the Cp50 was 4.1 μg/mL in the control group and 3.3 μg/mL in the nitrous oxide group. Calculated Cp95 values were 4.0 μg/mL and 5.1 μg/mL with and without 50% nitrous oxide respectively. Conclusions The Cp50 value for target-controlled infusion propofol during oocyte retrieval was significantly reduced by a factor of 1.24 (95% CI 1.07-1.44) with the use of 50% nitrous oxide.