Remifentanil Effect on Burst Suppression Ratio

Influence of Variable Plasma Concentrations of Remifentanil on Burst Suppression (BS) Event Rate in Electroencephalographic (EEG) Recordings of Human Subjects Undergoing Total Intravenous General Anesthesia (TIVA) Under Propofol

The goal of this clinical trial is to determine whether remifentanil has a facilitating effect on the generation of burst suppression by propofol in adult patients (18-60 years) candidates for elective surgery who require remifentanil and American Society of Anesthesiology (ASA) classification I or II. The main question it aims to answer are:

• To determine whether remifentanil has a facilitating effect on the generation of burst suppression by propofol.

Participants will undergo general anesthesia with remifentanil and propofol sequentially. After loss of consciousness, remifentanil will be adjusted to a medium or high concentration randomly and it will be determined at what concentration of propofol the burst suppressions are generated.

Then, the concentrations of propofol that generate burst suppression associated with either a medium or high concentration of remifentanil will be compared.

Study Overview

• Status: Recruiting
• Conditions: Anesthesia, Intravenous; Electroencephalography; Burst Suppression
• Intervention / Treatment: Drug: High dose of remifentanil; Drug: Medium dose of remifentanil

Detailed Description

Subjects will enter the ward, after which an 18 G intravenous cannula will be installed and will be monitored under the routinely applied ASA standard. Frontal EEG activity will be recorded using an anesthetic depth monitor and a baseline EEG will be recorded for 120 seconds with eyes closed. Subjects will then be preoxygenated. Once the oxygen concentration at the end of expiration reaches 90%, the administration of remifentanil will begin, under the Minto pharmacological model, to reach an effect site concentration of 7.5 ng/mL. Once the remifentanil concentration is reached, the infusion of propofol will begin at a rate of 15 mg/kg/h using Base Primea Orchestra, until loss of consciousness (LOC) is achieved. LOC will be defined as loss of response to verbal and tactile stimulation, which will be corroborated every 30 seconds. After this, the propofol infusion will be maintained at the concentration at which the LOC occurred, based on Marsh's pharmacological model, and rocuronium 0.6 mg/kg will be administered to facilitate orotracheal intubation.

Once the patient has been intubated, the remifentanil will be lowered to a concentration of 4 ng/mL and the surgery will continue. After 5 min after the LOC occurred, according to randomization, the concentration of remifentanil will remain at 4 ng/mL or increase to 7.5 ng/mL, and 10 min after the LOC occurred the propofol infusion rate will be changed to 15 mg/kg/h for 10 min. After this, the propofol concentration at which the LOC occurred will be returned and remifentanil will be maintained at 4 ng/mL. After 5 min after completing the previous step, remifentanil will be increased to 7.5 ng/mL or maintained at 4 ng/mL in the opposite way to what happened previously. After 10 min after completing the previous step, propofol will be dosed again at a fixed rate of 15 mg/kg/h for 10 min. Finally, after this time has elapsed, the concentration of propofol at which the LOC occurred will be returned and the remifentanil will be dosed according to the surgical requirements. Throughout the protocol, hemodynamics will be maintained with the usual management of drugs such as ephedrine in boluses or norepinephrine in continuous infusion.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Antonello Penna, MD, PhD; Phone Number: +56229788209; Email: apenna@uchile.cl

Study Locations

• Chile
  • RM
    • Santiago, RM, Chile, 7690306
      • Recruiting
      • Centro de Investigación Cínica Avanzada (CICA), Hospital Clinico de la Universidad de Chile
      • Contact: Daniela Ponce, Ing; Phone Number: 56229789405; Email: dponcedelavega@gmail.com
    • Santiago, RM, Chile, 7690306
      • Recruiting
      • Hospital Clinico de la Universidad de Chile

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• American Society of Anesthesiology I or II
• Elective surgery of low or intermediate risk

Exclusion Criteria:

• Neurological disease
• Psychiatric disease
• Use of psychoactive drugs or opioids
• Altered basal state of consciousness
• Allergy to propofol
• Body mass index > 35 kg/m2
• Pre-existing renal, cardiac and/or hepatic dysfunction
• Patient's refusal to participate

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: High dose; Propofol concentration which generate burst suppression at high dose of remifentanil	Drug: High dose of remifentanil; The dose of remifentanil will be changed to determine the concentration of propofol at which burst suppressions are generated
Active Comparator: Medium dose; Propofol concentration which generate burst suppression at medium dose of remifentanil	Drug: Medium dose of remifentanil; The dose of remifentanil will be changed to determine the concentration of propofol at which burst suppressions are generated

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Propofol estimated concentration by Marsh pharmacological model, which generates burst suppression	[mcg/mL]	During 10 minutes when propofol dosification is increased to 15 mg/kg/h

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Propofol estimated concentration by Marsh pharmacological model, which generates loss of consciousness	[mcg/mL]	Minutes, during anesthesia induction is performed
Mean arterial pressure during burst suppression	mmHg	During 10 minutes when propofol dosification is increased to 15 mg/kg/h
Total ephedrine dose	mg	During all protocol, 40 min
Maximal dose of norepinephrine	mcg/kg/min	During all protocol, 40 min
Bispectral index at burst suppression	(0-100), 0 indicates a flat electroencephalogram and 100 indicates to be awake.	During 10 minutes when propofol dosification is increased to 15 mg/kg/h

Collaborators and Investigators

• Sponsor: University of Chile

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2024
• Primary Completion (Estimated): August 31, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: January 24, 2024
• First Submitted That Met QC Criteria: January 24, 2024
• First Posted (Actual): February 1, 2024

Study Record Updates

• Last Update Posted (Actual): November 20, 2025
• Last Update Submitted That Met QC Criteria: November 17, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nervous System Diseases; Eye Diseases; Neurologic Manifestations; Sensation Disorders; Vision Disorders; Organic Chemicals; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Acids, Acyclic; Carboxylic Acids; Piperidines; Propionates; Remifentanil
• Other Study ID Numbers: OAIC: 1345/23

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