Measurement of the Second Gas Effect on Sevoflurane in Anaesthetised Patients

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.

Study Overview

• Status: Completed
• Conditions: Anesthesia
• Intervention / Treatment: Drug: Administration of N2O; Drug: No nitrous oxide

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 Type: Interventional
• Enrollment (Actual): 14
• Phase: Phase 4

Contacts and Locations

Study Locations

• Australia
  • Victoria
    • Melbourne, Victoria, Australia, 3084
      • Austin Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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.

Study Plan

How is the study designed?

Design Details

• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: N2O	Drug: Administration of N2O
Placebo Comparator: No N2O	Drug: No nitrous oxide

What is the study measuring?

Primary Outcome Measures

Outcome Measure
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

Outcome Measure
Fa/FI and FA/FI for N2O will also be recorded.

Collaborators and Investigators

• Sponsor: Austin Health
• Investigators: Principal Investigator: Philip J Peyton, MD FANZCA, Austin Health

Study record dates

Study Major Dates

• Study Start: May 1, 2006
• Primary Completion: December 7, 2022
• Study Completion (Actual): September 1, 2006

Study Registration Dates

• First Submitted: May 2, 2006
• First Submitted That Met QC Criteria: May 2, 2006
• First Posted (Estimate): May 3, 2006

Study Record Updates

• Last Update Posted (Estimate): June 24, 2015
• Last Update Submitted That Met QC Criteria: June 23, 2015
• Last Verified: August 1, 2008

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Central Nervous System Depressants; Peripheral Nervous System Agents; Analgesics; Sensory System Agents; Anesthetics, General; Anesthetics; Analgesics, Non-Narcotic; Anesthetics, Inhalation; Nitrous Oxide
• Other Study ID Numbers: 02531

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No