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Effect of Nitrous Oxide (N2O) on Intraocular Pressure in Healthy Volunteers

This study has been completed.
Robert L. Bacon Medical Foundation
Research to Prevent Blindness
Information provided by (Responsible Party):
Kirk Lalwani, Oregon Health and Science University Identifier:
First received: August 27, 2009
Last updated: September 15, 2014
Last verified: September 2014

The purpose of this study is to learn if breathing nitrous oxide (also known as "laughing gas") changes the pressure in a person's eyes. Some patients who need regular eye exams to measure their eye pressure often need to be put to sleep with medicine in order to complete the eye exam. Some of these medicines are known to cause changes in a person's eye pressure. Because of this, such medicines are avoided if the eye doctor needs to measure the patient's eye pressure. One medicine that is frequently used to put patients to sleep is nitrous oxide. No one really knows what effect nitrous oxide might have on a persons' eye pressure. The investigators are interested to see if nitrous oxide causes an increase, decrease, or no change in eye pressure. The investigators also want to investigate if there is a difference in the effects of nitrous oxide on eye pressure between males and females. Understanding these effects of nitrous oxide is important because during such eye exams, the eye doctor uses the pressure measurements to make important decisions about treatment and surgery options for the patient.

The investigators hypothesize that the use of inhaled nitrous oxide (N2O) will result in a decrease in IOP in healthy volunteers.

The investigators aim to determine the magnitude and duration of change, if any, in IOP caused by inhalation of N2O, and to assess if the gender of the patient has a role in this effect.

Condition Intervention Phase
Glaucoma Sedation Drug: Nitrous oxide Phase 4

Study Type: Interventional
Study Design: Intervention Model: Single Group Assignment
Masking: Single (Investigator)
Primary Purpose: Diagnostic
Official Title: Effect of N2O on Intraocular Pressure in Healthy Volunteers

Resource links provided by NLM:

Further study details as provided by Kirk Lalwani, Oregon Health and Science University:

Primary Outcome Measures:
  • Change in Intraocular Pressure During Nitrous Oxide Sedation [ Time Frame: Before, during and after administration of nitrous oxide (45 minutes total) ]

Enrollment: 20
Study Start Date: August 2009
Study Completion Date: October 2011
Primary Completion Date: October 2011 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: Nitrous oxide administration
All 20 healthy volunteers had their intraocular pressure (IOP) measured at baseline and then after 3, 6, 9, and 12 minutes of nitrous oxide administration, and then after 5, 10, and 15 minutes of breathing room air. There was therefore only one study arm, with each individual serving as their control for baseline and then intervention values of IOP measurement.
Drug: Nitrous oxide
Nitrous oxide sedation by inhalation
Other Name: N2O

Detailed Description:
An initial pre-anesthetic evaluation and physical examination will be performed by an attending anesthesiologist, and an eye exam will be performed by an attending ophthalmologist to determine suitability for inclusion according to the above criteria. Ideally the eye exam will take place immediately prior to conduction of the study. However, logistical restraints may require that the eye exam take place at a separate time/date prior to conduction of the study. IOPs will be measured by the attending ophthalmologist (B.E.) who will be blinded to the actual readings of the Tonopen by means of a small screen, and a single trained observer (E.F.) will record observations from the Tonopen. The nitrous oxide sedation will be managed by the attending anesthesiologist (K.L.). All patients will be monitored throughout using standardized monitoring (continuous EKG, non-invasive BP, and continuous pulse oximetry).

Ages Eligible for Study:   18 Years to 40 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Adults aged 18-40
  • American Society of Anesthesiologists Physical Classification System (ASA) Status 1-2
  • Nil per os (NPO) prior to study (2 hrs clear liquids, 4 hrs milk, 6 hrs light food, 8 hrs heavy/greasy food)

Exclusion Criteria:

  • Lack of volunteer consent
  • Pregnancy
  • History of features suggestive of a difficult airway on pre-anesthetic evaluation and physical examination
  • Active gastroesophageal reflux disease
  • Active obstructive sleep apnea
  • History of recent trauma
  • History of pneumothorax or lung cyst
  • History of Vitamin B12 deficiency
  • History of recent middle ear surgery (<3months)
  • Current or recent (<3 weeks) respiratory tract infection
  • Any acute illness or exacerbation of chronic illness such as asthma, chronic lung disease etc.
  • Any history of cardiac ischemia (angina), myocardial infarction, or cardiac dysrhythmia.
  • Myopia greater than -3 spherical equivalents or hyperopia greater than +3 spherical equivalents
  • History of eye surgery of any sort, including refractive surgery, cataracts, and vitrectomy
  • History of any ocular disease or infection
  Contacts and Locations
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Please refer to this study by its identifier: NCT00967694

United States, Oregon
Portland, Oregon, United States, 97239
Sponsors and Collaborators
Oregon Health and Science University
Robert L. Bacon Medical Foundation
Research to Prevent Blindness
Principal Investigator: Kirk Lalwani, MD,FRCA,MCR Oregon Health and Science University
  More Information

Responsible Party: Kirk Lalwani, Associate Professor, Anesthesiology and Pediatrics, Oregon Health and Science University Identifier: NCT00967694     History of Changes
Other Study ID Numbers: IRB00005402
Study First Received: August 27, 2009
Results First Received: April 24, 2014
Last Updated: September 15, 2014

Keywords provided by Kirk Lalwani, Oregon Health and Science University:
Nitrous oxide

Additional relevant MeSH terms:
Ocular Hypertension
Eye Diseases
Nitrous Oxide
Anesthetics, Inhalation
Anesthetics, General
Central Nervous System Depressants
Physiological Effects of Drugs
Analgesics, Non-Narcotic
Sensory System Agents
Peripheral Nervous System Agents processed this record on September 21, 2017