The 50:50 Nitrous Oxide vs 2% Lidocaine Challenge

May 25, 2026 updated by: Ana Cvetković, Institute for Oncology and Radiology of Serbia

The 50:50 Nitrous Oxide Challenge: A Prospective Randomised Trial - Needle, Meet Your Match

The main goal of the project is to assess pain levels and patient comfort during the administration of a 50:50 Nitrous Oxide/Oxygen gas mixture, in comparison to the same parameters under the standard method used at our institution, which includes injecting a local anaesthetic at the site of planned puncture for central venous catheterisation.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
62

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Serbia
    • Savski Venac
      • Belgrade, Savski Venac, Serbia, 11000
        • Recruiting
        • Institute for Oncology and Radiology of Serbia
        • Contact:
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Subjects who have not previously received Nitrous Oxide.
  • Subjects of both sexes, aged between 18 and 65 inclusive.
  • Subjects who have signed informed consent with full disclosure; no study-related procedure may begin until the subject signs the consent form.

Exclusion Criteria:

  • Infection at the planned puncture site.
  • Pregnancy.
  • Intracranial hypertension.
  • Vitamin B12 deficiency.
  • Hemodynamic instability.
  • BMI over 35.
  • Glasgow Coma Scale (GCS) score less than 15.
  • Presence of chronic pain.
  • Neurological disorders.
  • Hematologic disorders.
  • More than two attempts at venous puncture (Subject Withdrawal Criterion).
  • Subject experienced an adverse event requiring early discontinuation (Subject Withdrawal Criterion).
  • Withdrawal of consent by the subject (Subject Withdrawal Criterion)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Nitrous Oxide Group
This will be the experimental group in which the patients will receive a mixture of gases to assess the efficacy of the treatment compared to the control.
Drug: Nitrous Oxide-Oxygen
After placing the patient in the appropriate supination + Trendelenburg position, the operative field (neck and subclavian region) is prepared using antiseptic measures.Five minutes before needle insertion, a mask connected to a 50:50 Nitrous Oxide/Oxygen cylinder with a flow rate of 6 liters per minute is placed on the patient's face and held by the patient. The mask has a valve that opens only when the patient creates negative pressure during inhalation.The patient is instructed to breathe spontaneously; the mask is removed once the catheter is inserted into the target vein or after cessation of painful stimulation.
Other Names:
  • Experimental Treatment
Active Comparator: Lidocaine 2%
The control group receiving the standard of care for this intervention.
Drug: Lidocaine 2% Injectable Solution
After placing the patient in the appropriate supination + Trendelenburg position, the operative field (neck and subclavian region) is prepared using antiseptic measures. Then, under ultrasound control, the most favorable central vein for puncture is determined (v. jugularis interna or v. subclavia) and a 25-gauge needle is used to infiltrate the skin and subcutaneous tissue above the selected vein with local anesthetic. Five minutes after infiltration, puncture of the selected vein is performed using the Seldinger technique. Continuous communication with the patient is maintained throughout the procedure.
Other Names:
  • Control

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Pain Intensity During Needle Insertion
Time Frame: At the time of needle insertion
Assessed using a standard Numeric Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain). Higher scores indicate greater pain intensity.
At the time of needle insertion
Pain Intensity During Catheter Placement
Time Frame: During catheter placement
Assessed using a standard Numeric Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain). Higher scores indicate greater pain intensity.
During catheter placement
Pain Intensity Post-Intervention
Time Frame: 2 minutes after gas inhalation (Treatment 1) or 2 minutes post-intervention (Treatment 2)
Assessed using a standard Numeric Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain). Higher scores indicate greater pain intensity.
2 minutes after gas inhalation (Treatment 1) or 2 minutes post-intervention (Treatment 2)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Patient Anxiety Score
Time Frame: Post-intervention (at the conclusion of the central venous catheterization procedure)
Assessed using a standard Numeric Rating Scale (NRS) ranging from 0 (no anxiety) to 10 (worst imaginable anxiety). Higher scores indicate greater anxiety levels.
Post-intervention (at the conclusion of the central venous catheterization procedure)
Patient Satisfaction Score
Time Frame: Post-intervention (at the conclusion of the central venous catheterization procedure)
Assessed using a Numeric Rating Scale (NRS) where patients rate their overall satisfaction with the anesthetic method. The scale ranges from 0 (completely unsatisfied) to 4 (completely satisfied). Higher scores indicate greater satisfaction.
Post-intervention (at the conclusion of the central venous catheterization procedure)
Incidence of Treatment-Related Adverse Events
Time Frame: From the start of the intervention through 30 minutes post-procedure
Percentage of participants experiencing specific adverse events, including nausea/vomiting, unpleasant dreams, paresthesias, dizziness, and euphoria, as recorded by subjective patient reports.
From the start of the intervention through 30 minutes post-procedure

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Institute for Oncology and Radiology of Serbia

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Ana Cvetković, MD, PhD, Institute for Oncology and Radiology of Serbia

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
June 6, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
June 6, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 1, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
May 25, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 25, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
June 1, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
June 1, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 25, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 01-1/2025/1264

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

There is no current plan to share individual participant data to external registries.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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