Original Article

Nitrous Oxide and Nitrous Oxide-Free Low-Flow Anesthesia Using Bispectral Index Monitoring: Effects on Hemodynamics, Recovery Times, Volatile Anesthetic Consumption and Costs

  • Bengü Gülhan Köksal
  • Volkan Hancı
  • Gülay Erdoğan
  • Bülent Serhan Yurtlu
  • Rahsan Dilek Okyay
  • Hilal Ayoğlu
  • Işıl Özkoçak Turan

Received Date: 01.10.2010 Accepted Date: 13.10.2010 Med Bull Haseki 2010;48(4):132-138


In this study, we aimed to compare the effects of desflurane- N2O and desflurane-fentanyl combinations on hemodynamics, recovery times, volatile anesthetic consumption and costs in low-flow desflurane anesthesia by bispectral index (BIS) monitoring of depth of anesthesia.

Methods: After approval of ethics committee and obtaining patient consents, 60 patients were divided into two equal groups randomly. Non-invasive blood pressure measurement, ECG, SpO2 and BIS were monitored. All patients received 10 L .min-1 100% oxygen with mask for 5 minute before intubation. 2 mg.kg-1 propofol, 2 μg.kg-1 fentanyl and 0.6 mg.kg-1 rocuronium bromide were administered at induction in both groups. Desfluran 6% was chosen for anesthesia maintenance. Group 1 received 50% O2-N2O mixture in 6 L.min-1 and Group 2 received 50% O2-air mixture in 6 L.min-1 as carrier gas. Low-flow anesthesia (1 L.min-1) was started after a 10-min period of initial high flow (6 L.min-1 ). In Group 2, infusion of fentanyl was begun in 1 μg.kg.hour-1 rate. Desflurane level was adjusted at a main BIS value of 40-60. Blood pressure, heart rate, FiO2, etO2, FiN22, EtN2O, FiCO2, EtCO2, Fidesfluran and Etdesflurane were recorded.


There were no significant differences between the two groups in terms of heart rate, arterial blood pressure, settings of desfluran and recovery time. BIS values (p<0.001) and anesthetic agent costs (p<0.001) were higher in Group 2.


Using fentanyl infusion instead of nitrous oxide in low flow-anesthesia with desflurane did not alter the hemodynamic parameters. Fentanyl infusion with medical air-oxygen as carrier gas is an alternative technique, but increases BIS values and anesthetic agent costs.

Keywords: low-flow anesthesia, desflurane, N2O, BIS, anesthetic gas costs.

Full Text (Turkish)