Minimal Flow Anesthesia and Infection Risk

NCT07092046 | Completed

• 1 other identifier: EthicsApproval: E2-25-11471
• Study Type: interventional
• Target: 140
• Locations: 1 country
• Sites: 1

Brief Summary

This study is being done to find out if the heat and moisture that build up during minimal flow anesthesia can lead to the growth of germs (microorganisms) inside the anesthesia equipment. Minimal flow anesthesia (using fresh gas flow of 0.5 liters per minute or less) is known to help protect the lungs and the environment. However, it may also cause water to collect in the equipment, which could allow germs to grow. In this study, we want to see whether this type of anesthesia is safe when it comes to the risk of germs in the equipment.

Conditions

Infection Risk; Anesthesia Circuit; Microbial Colonization; Anesthesia Equipment Bacterial Contamination; Minimal Flow Anesthesia; General Anaesthesia; Inhalation Anesthesia

Keywords

minimal flow anesthesia; Anesthesia Circuit; Infection Risk; Microbial Colonization

Outcome Measures

Primary Outcomes (1)

• Assessment of Bacterial Contamination in Anesthesia Circuits and Nasopharyngeal Swab Samples

  The aim of this study is to evaluate and compare bacterial contamination in the inspiratory and expiratory limbs of anesthesia circuits and in the nasopharyngeal region of patients undergoing elective surgery under either minimal-flow (0.5 L/min) or normal-flow (2 L/min) inhalation anesthesia. A total of four sterile swab samples will be collected from each patient: one nasopharyngeal swab upon arrival to the operating room, and three circuit swabs-two taken from the inspiratory and expiratory limbs before circuit connection, and one after circuit disconnection at the end of the procedure. All samples will be cultured and incubated under appropriate conditions, and microbial identification will be performed to the species level using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

  During the observational period, which begins 10 minutes prior to anesthesia induction and continues until 10 minutes after the cessation of anesthesia.

Secondary Outcomes (5)

• Changes in Body Temperature During Anesthesia

  From 10 minutes before induction to 45 minutes after anesthesia termination

• Heart Rate at Defined Perioperative Time Points (bpm)

  From 10 minutes before induction to 45 minutes after anesthesia termination

• Peripheral Oxygen Saturation (SpO₂) at Defined Perioperative Time Points (%)

  From 10 minutes before induction to 45 minutes after anesthesia termination

• End-Tidal Carbon Dioxide (ETCO₂) Levels at Defined Perioperative Time Points (mmHg)

  From 10 minutes before induction to 45 minutes after anesthesia termination

• Mean Arterial Pressure at Defined Perioperative Time Points (mmHg)

  From 10 minutes before induction to 45 minutes after anesthesia termination

Study Arms (2)

Minimal Flow Anesthesia (0.5 L/min)

ACTIVE COMPARATOR

Participants in this group will receive minimal-flow inhalation anesthesia, administered at a fresh gas flow rate of 0.5 L/min (Liters per minute). This technique helps preserve heat and humidity within the anesthesia circuit while reducing both anesthetic gas waste and environmental impact. The study aims to evaluate whether this lower flow rate contributes to circuit condensation and microbial colonization in the breathing system.

Drug: Sevoflurane (Volatile Anesthetic); Drug: Propofol 1%; Drug: Remifentanil 2 MG; Drug: Rocuronium 50 mg/5 ml; Drug: Lidocaine %2 ampoule; Drug: Ephedrine Hydrochloride 0,05 mg/ml ampoule; Drug: Sugammadex 200 MG in 2 ML Injection; Drug: Fentanyl (IV); Drug: Atropine Sulphate 0.5mg/ml ampoule; Procedure: Peripheral Intravenous Cannulation; Procedure: Mechanical Ventilation; Drug: Crystalloid solutions; Procedure: Endotracheal Intubation; Procedure: American Society of Anesthesiologists (ASA) Standard Monitors; Procedure: Minimal-Flow Anesthesia; Diagnostic Test: Anesthesia Circuit Sampling; Procedure: Body Temperature Monitoring; Diagnostic Test: Nasopharyngeal Swab Collection; Diagnostic Test: Microbiological Culture and Identification

Standard Flow Anesthesia (2 L/min)

ACTIVE COMPARATOR

Participants in this group will receive inhalation anesthesia with a continuous fresh gas flow rate of 2 liters per minute (L/min) throughout the surgical procedure. This represents conventional-flow anesthesia, in which higher gas turnover allows for rapid adjustments in anesthetic concentrations but may lead to increased loss of heat and humidity within the breathing circuit.

Drug: Sevoflurane (Volatile Anesthetic); Drug: Propofol 1%; Drug: Remifentanil 2 MG; Drug: Rocuronium 50 mg/5 ml; Drug: Lidocaine %2 ampoule; Drug: Ephedrine Hydrochloride 0,05 mg/ml ampoule; Drug: Sugammadex 200 MG in 2 ML Injection; Drug: Fentanyl (IV); Drug: Atropine Sulphate 0.5mg/ml ampoule; Procedure: Peripheral Intravenous Cannulation; Procedure: Mechanical Ventilation; Drug: Crystalloid solutions; Procedure: Endotracheal Intubation; Procedure: American Society of Anesthesiologists (ASA) Standard Monitors; Procedure: Normal-Flow Anesthesia; Diagnostic Test: Anesthesia Circuit Sampling; Procedure: Body Temperature Monitoring; Diagnostic Test: Nasopharyngeal Swab Collection; Diagnostic Test: Microbiological Culture and Identification

Interventions

Sevoflurane (Volatile Anesthetic) DRUG

An inhalational anesthetic agent will be used for the maintenance of anesthesia, administered at a concentration of 2-3% in a gas mixture consisting of 40% oxygen and air.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Propofol 1% DRUG

An intravenous hypnotic agent will be used for anesthesia induction at a dose of 2-3 mg/kg.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Remifentanil 2 MG DRUG

A short-acting opioid will be administered intravenously for maintenance of anesthesia at a dose of 0.02-0.2 micrograms per kilogram per minute (μg/kg/min).

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Rocuronium 50 mg/5 ml DRUG

A neuromuscular blocking agent will be administered intravenously at a dose of 0.6-1.2 mg/kg for induction, and 0.15 mg/kg for maintenance of muscle relaxation during surgery.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Lidocaine %2 ampoule DRUG

This agent will be administered intravenously at a dose of 1-1.5 mg/kg prior to anesthesia induction to reduce injection pain and facilitate smooth induction.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Ephedrine Hydrochloride 0,05 mg/ml ampoule DRUG

This agent will be administered intravenously at a dose of 0.1 mg/kg to treat intraoperative hypotension that does not respond to fluid replacement or adjustment of anesthetic depth.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Sugammadex 200 MG in 2 ML Injection DRUG

Sugammadex will be administered intravenously at a dose of 2 mg/kg or 4 mg/kg, depending on the degree of neuromuscular blockade.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Fentanyl (IV) DRUG

Fentanyl will be administered intravenously as part of the anesthesia induction regimen, at a dose ranging from 1 to 2 micrograms per kilogram (µg/kg).

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Atropine Sulphate 0.5mg/ml ampoule DRUG

In cases of intraoperative bradycardia, defined as a heart rate (HR) below 45 beats per minute (bpm), 0.5 mg of the agent will be administered intravenously.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Peripheral Intravenous Cannulation PROCEDURE

All participants received peripheral intravenous cannulation using 18-20 G IV cannulas placed on the dorsum of the hand before anesthesia induction.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Mechanical Ventilation PROCEDURE

Following endotracheal intubation, mechanical ventilation will be initiated using volume-controlled settings, with a tidal volume (TV) of 6-8 mL/kg, respiratory rate (RR) of 12 breaths per minute, and fraction of inspired oxygen (FiO₂) set at 50%. Ventilator parameters will be adjusted to maintain end-tidal carbon dioxide (ETCO₂) between 30 and 36 mmHg.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Crystalloid solutions DRUG

Participants will receive calculated maintenance fluid therapy with crystalloids administered via intravenous infusion, both prior to and throughout the surgical procedure.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Endotracheal Intubation PROCEDURE

Following induction of anesthesia and establishment of neuromuscular blockade, endotracheal intubation will be performed using a standard technique in all participants.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

American Society of Anesthesiologists (ASA) Standard Monitors PROCEDURE

Routine monitoring in accordance with American Society of Anesthesiologists (ASA) guidelines, including noninvasive blood pressure, electrocardiogram (ECG, D2 lead), end-tidal carbon dioxide (ETCO₂), and peripheral oxygen saturation (SpO₂), will be performed in all patients starting from the preoperative period and continuing throughout the surgery.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Minimal-Flow Anesthesia PROCEDURE

In the minimal-flow anesthesia group, after induction and once a minimum alveolar concentration (MAC) of 1 is achieved, the fresh gas flow will be reduced to 0.5 L/min with a mixture of 45% oxygen (O₂) and 55% air, and maintained throughout the surgical procedure. At the end of surgery, the flow will be increased to 3 L/min to facilitate emergence. Disposable anesthesia circuits, bacterial filters, and face masks will be used for each patient, and carbon dioxide (CO₂) absorbers will be replaced daily.

Minimal Flow Anesthesia (0.5 L/min)

Normal-Flow Anesthesia PROCEDURE

In the normal-flow anesthesia group, after induction and once a minimum alveolar concentration (MAC) of 1 is achieved, the fresh gas flow will be adjusted to 2 L/min and maintained during the surgical procedure. For emergence, the flow will be increased to 3 L/min. Disposable anesthesia circuits will be used, and daily maintenance protocols, including replacement of carbon dioxide (CO₂) absorbers, will be applied in the same manner as in the minimal-flow group.

Standard Flow Anesthesia (2 L/min)

Anesthesia Circuit Sampling DIAGNOSTIC_TEST

Sterile swab samples will be collected from both the inspiratory and expiratory limbs of the anesthesia circuit-once prior to circuit connection and again immediately after disconnection at the end of the surgical procedure. All samples will be processed for microbial culture and species-level identification.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Body Temperature Monitoring PROCEDURE

In addition to routine monitoring-including electrocardiogram (ECG), non-invasive blood pressure, peripheral oxygen saturation (SpO₂), and end-tidal carbon dioxide (ETCO₂)-body temperature will be continuously monitored in both study groups throughout the surgical procedure using appropriate thermal sensors. Temperature measurements will be recorded at 5-minute intervals and used to assess the impact of different fresh gas flow rates on intraoperative thermoregulation.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Nasopharyngeal Swab Collection DIAGNOSTIC_TEST

A sterile nasopharyngeal swab (Dry SWAB) will be collected from each patient upon arrival in the operating room, prior to anesthesia induction. Each sample will be labeled with the patient's identification number, date, time, and collection site, and will be transferred in appropriate transport medium to the microbiology laboratory for culture and microbiological analysis.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Microbiological Culture and Identification DIAGNOSTIC_TEST

All collected swab samples-including both nasopharyngeal and anesthesia circuit specimens-will be cultured using the serial dilution method on 5% sheep blood agar within 15 minutes of arrival at the microbiology laboratory. Cultures will be incubated at 35-37°C for 48 hours. Colony growth will be evaluated by a clinical microbiologist, and microorganisms will be identified to the species level using an automated MALDI-TOF MS (Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry) system.

Minimal Flow Anesthesia (0.5 L/min); Standard Flow Anesthesia (2 L/min)

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• A total of 140 voluntary patients will be included in the study.
• Patients will be aged between 18 and 65 years.
• Both male and female patients will be enrolled.
• All patients will be classified as c physical status I or II.
• Patients will undergo elective surgical procedures.
• The study will be conducted in the operating rooms of Ankara Bilkent City Hospital, affiliated with the Ministry of Health of the Republic of Türkiye.

You may not qualify if:

• Patients who do not consent to participate
• Patients outside the age range of 18-65 years
• Patients classified as ASA (American Society of Anesthesiologists) III, IV, or V
• Patients scheduled for emergency surgery
• Patients with uncontrolled hypertension
• Patients with significant cardiac diseases (e.g., heart failure, coronary artery disease, arrhythmia, valvular heart disease)
• Patients with significant pulmonary diseases (e.g., Chronic Obstructive Pulmonary Disease, Restrictive Pulmonary Disease, Asthma)
• Patients with neuromuscular disorders
• Patients with poorly controlled diabetes mellitus
• Patients with metabolic disorders
• Patients with immunodeficiency
• Patients with significant anemia
• Patients with bleeding diathesis
• Patients with liver and/or kidney diseases
• History of cardiac surgery

Sponsors & Collaborators

• Ankara City Hospital Bilkent: lead

Study Sites (1)

Ankara Bilkent City Hospital

Ankara, Turkey (Türkiye)

Location

MeSH Terms

Conditions

Communicable Diseases

Interventions

Sevoflurane; Propofol; Remifentanil; Rocuronium; Sugammadex; Injections; Fentanyl; Atropine; Respiration, Artificial; Crystalloid Solutions; Intubation, Intratracheal

Condition Hierarchy (Ancestors)

Infections; Disease Attributes; Pathologic Processes; Pathological Conditions, Signs and Symptoms

Intervention Hierarchy (Ancestors)

Methyl Ethers; Ethers; Organic Chemicals; Hydrocarbons, Fluorinated; Hydrocarbons, Halogenated; Hydrocarbons; Phenols; Benzene Derivatives; Hydrocarbons, Aromatic; Hydrocarbons, Cyclic; Propionates; Acids, Acyclic; Carboxylic Acids; Piperidines; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Androstanols; Androstanes; Steroids; Fused-Ring Compounds; Polycyclic Compounds; gamma-Cyclodextrins; Cyclodextrins; Macrocyclic Compounds; Dextrins; Starch; Glucans; Polysaccharides; Carbohydrates; Drug Administration Routes; Drug Therapy; Therapeutics; Atropine Derivatives; Tropanes; Azabicyclo Compounds; Aza Compounds; Belladonna Alkaloids; Solanaceous Alkaloids; Alkaloids; Bridged Bicyclo Compounds, Heterocyclic; Heterocyclic Compounds, Bridged-Ring; Airway Management; Resuscitation; Emergency Treatment; Respiratory Therapy; Isotonic Solutions; Solutions; Pharmaceutical Preparations; Intubation; Investigative Techniques

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: OTHER
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Specialist Physician

Study Record Dates

• First Submitted: July 20, 2025
• First Posted: July 29, 2025
• Study Start: July 1, 2025
• Primary Completion: July 1, 2025
• Study Completion: April 15, 2026
• Last Updated: April 28, 2026

Record last verified: 2026-04

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)