Evaluation of Sevoflurane Consumption During Initial Phase of Minimal-Flow Anesthesia in Retrograde Intrarenal Surgery

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

62 participants

Study Classification

INTERVENTIONAL

Study Start Date

2024-10-01

Study Completion Date

2025-09-01

Brief Summary

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This study aimed to compare the effects of minimal-flow (0.5 L/min) and low-flow (1.0 L/min) sevoflurane anesthesia on agent consumption, anesthetic depth, and cardiorespiratory safety during retrograde intrarenal surgery (RIRS). A total of 62 adult patients undergoing elective RIRS were enrolled in this single-center interventional trial. Patients were divided into two groups based on the fresh gas flow rate used during the maintenance phase of anesthesia. The primary outcome was total sevoflurane consumption at the end of anesthesia. Secondary outcomes included time to reach 1 minimum alveolar concentration (MAC), vaporizer shut-off time, BIS values, MAC levels, and respiratory parameters. The study found that minimal-flow anesthesia was as effective and safe as low-flow anesthesia, with lower agent consumption and no adverse effects on hemodynamic or respiratory parameters. These findings support the use of minimal-flow anesthesia for improved cost-efficiency and environmental sustainability.

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Detailed Description

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This prospective, single-center, interventional study was designed to evaluate and compare the effects of minimal-flow and low-flow anesthesia on sevoflurane consumption, anesthetic depth, and respiratory parameters during retrograde intrarenal surgery (RIRS). After obtaining ethics committee approval (Decision No: 2024/16/925, Date: 17.09.2024), a total of 62 adult patients undergoing elective RIRS under general anesthesia were enrolled and divided into two groups based on the fresh gas flow rate used during the maintenance phase of anesthesia.

In Group 1 (Minimal-flow group), the fresh gas flow was reduced to 0.5 L/min after the initial 10 minutes of anesthesia. In Group 2 (Low-flow group), a 1.0 L/min flow rate was maintained. Both groups received the same induction and maintenance protocols with sevoflurane, and depth of anesthesia was monitored via BIS (Bispectral Index). Key variables measured included the total amount of sevoflurane consumed (mL), the time to reach 1 MAC, the vaporizer shut-off time, intraoperative BIS and MAC values, EtCO₂, and respiratory rate. Safety outcomes such as hemodynamic stability and desaturation were also recorded.

The primary outcome was total sevoflurane consumption. Secondary outcomes included anesthetic depth consistency (BIS/MAC), respiratory parameters, and time-based metrics. Statistical analysis revealed that minimal-flow anesthesia significantly reduced sevoflurane usage without compromising patient safety or anesthetic depth.

The results support the clinical use of minimal-flow anesthesia as a safe, cost-effective, and environmentally favorable alternative to low-flow techniques in selected urological procedures.

Conditions

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Retrograde Intrarenal Surgery (RIRS) Urolithiasis Minimal-flow Anesthesia Sevoflurane Anesthetic Consumption Inhalational Anesthesia Anesthesia Depth Monitoring

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

PARALLEL

This was a prospective, two-arm, parallel-group study in which patients undergoing retrograde intrarenal surgery (RIRS) were randomly assigned to receive either minimal-flow (0.5 L/min) or low-flow (1.0 L/min) sevoflurane anesthesia. Participants were allocated to one group only and followed independently throughout the procedure. No crossover between groups occurred. The study aimed to compare anesthetic consumption, depth of anesthesia, and cardiorespiratory safety between the two anesthetic flow techniques.

Primary Study Purpose

TREATMENT

Blinding Strategy

NONE

Study Groups

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Minimal-flow Sevoflurane Group

Participants in this group received general anesthesia using sevoflurane with a fresh gas flow rate reduced to 0.5 L/min after the initial 10 minutes of induction. Anesthesia depth was monitored using BIS, and agent consumption and respiratory parameters were recorded throughout the retrograde intrarenal surgery (RIRS) procedure.

Group Type EXPERIMENTAL

Sevoflurane Anesthesia with Minimal-flow

Intervention Type DRUG

Patients received general anesthesia with sevoflurane. After induction, the fresh gas flow rate was reduced to 0.5 L/min during the maintenance phase of anesthesia for retrograde intrarenal surgery (RIRS). Agent consumption and anesthetic depth (via BIS and MAC) were monitored.

Low-flow Sevoflurane Group

Participants in this group received general anesthesia using sevoflurane with a consistent 1.0 L/min fresh gas flow during the maintenance phase. BIS monitoring, agent consumption, and respiratory parameters were recorded throughout the retrograde intrarenal surgery (RIRS).

Group Type ACTIVE_COMPARATOR

Sevoflurane Anesthesia with Low-flow

Intervention Type DRUG

Patients received general anesthesia with sevoflurane. A fresh gas flow rate of 1.0 L/min was maintained during the maintenance phase of anesthesia for retrograde intrarenal surgery (RIRS). BIS, MAC, and respiratory parameters were recorded.

Interventions

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Sevoflurane Anesthesia with Minimal-flow

Patients received general anesthesia with sevoflurane. After induction, the fresh gas flow rate was reduced to 0.5 L/min during the maintenance phase of anesthesia for retrograde intrarenal surgery (RIRS). Agent consumption and anesthetic depth (via BIS and MAC) were monitored.

Intervention Type DRUG

Sevoflurane Anesthesia with Low-flow

Patients received general anesthesia with sevoflurane. A fresh gas flow rate of 1.0 L/min was maintained during the maintenance phase of anesthesia for retrograde intrarenal surgery (RIRS). BIS, MAC, and respiratory parameters were recorded.

Intervention Type DRUG

Eligibility Criteria

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Inclusion Criteria

* Adults aged 18 to 65 years

ASA (American Society of Anesthesiologists) Physical Status I or II

Scheduled to undergo elective retrograde intrarenal surgery (RIRS) under general anesthesia

Provided written informed consent

Able to cooperate with preoperative evaluation procedures

Exclusion Criteria

* ASA Physical Status III or higher

History of respiratory disease (e.g., asthma, COPD, restrictive lung disease)

Known hepatic or renal dysfunction

Neurological or psychiatric disorders that may affect BIS monitoring or anesthetic response

Known allergy or hypersensitivity to sevoflurane or other volatile anesthetics

Pregnancy or breastfeeding

Obesity (BMI \> 30 kg/m²)

Anticipated difficult airway or history of intubation complications

Participation in another clinical trial within the past 30 days

Minimum Eligible Age

18 Years

Maximum Eligible Age

65 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

No