Measurement of the Second Gas Effect on Sevoflurane in Anaesthetised Patients

Phase 4

Completed

• Conditions: Anesthesia
• Interventions: Drug: Administration of N2O; Drug: No nitrous oxide

• Registration Number: NCT00321191
• Lead Sponsor: Austin Health

Brief Summary

This study is investigating the "second gas effect", a phenomenon produced by the uptake of nitrous oxide (N2O) by the lungs, during the course of a typical anaesthetic. The effect is to increase the concentration of other breathed gases in the lung. These include oxygen and volatile anaesthetic agents such as sevoflurane, which are also normally administered along with N2O. We wish to i) measure the magnitude of the second gas effects on both blood and expired concentrations of sevoflurane (Part 1), and ii) see if a demonstrable difference exists between the effects on blood and expired concentrations.

Detailed Description

This study is investigating the "second gas effect", a phenomenon produced by the uptake of nitrous oxide (N2O) by the lungs, during the course of a typical anaesthetic. The effect is to increase the concentration of other breathed gases in the lung. These include oxygen and volatile anaesthetic agents such as sevoflurane, which are also normally administered along with N2O.

While the second gas effect has been demonstrated previously, by measuring the concentration of volatile anaesthetic in the expired breath, no study has yet shown that it has a significant effect on the concentrations in the blood. The blood concentration is in fact more important, as it directly determines the concentration of anaesthetic reaching the brain, and therefore the effect on the depth of anaesthesia. The second gas effect on blood concentrations may be more powerful than that on expired concentrations, due to the detrimental effect of anaesthesia on the evenness of distribution of ventilation and blood flow in the lung.

The proposed study will have two parallel components or Parts. We wish to i) measure the magnitude of the second gas effects on both blood and expired concentrations of sevoflurane (Part 1), and ii) see if a demonstrable difference exists between the effects on blood and expired concentrations.

Study Timeline

• Study Start: 2006-05
• Study First Submitted: 2006-05-02
• Study First Submitted QC: 2006-05-02
• Study First Posted: 2006-05-03
• Study Completion: 2006-09
• Status Verified: 2008-08
• Last Update Submitted: 2015-06-23
• Last Update Posted: 2015-06-24

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 14

Inclusion Criteria

• Patients scheduled for elective surgery requiring relaxant general anaesthesia with arterial blood pressure monitoring via an arterial line.

Exclusion criteria:

• Patients with moderately or severely impaired respiratory disease (FEV1 < 1.5L, or FVC < 2.0L).
• Patients under 18 years of age.
• Morbidly obese patients: BMI > 30
• Patients unable to give informed consent.

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
N2O	Administration of N2O	-
No N2O	No nitrous oxide	-

Primary Outcome Measures

Name	Time	Method
Fa/FI sevoflurane in 100% O2 vs in 70% N2O and 30% O2 during 1st 60 min anaesthesia
Change in Fa/FI sevoflurane in 100% O2 vs in 70% N2O and 30% O2 after 60 minutes anaesthesia

Secondary Outcome Measures

Name	Time	Method
Fa/FI and FA/FI for N2O will also be recorded.

Trial Locations

Locations (1)

Austin Hospital; 🇦🇺 Melbourne, Victoria, Australia