Comparison of Two Magnesium Sulfate Protocols in Opioid-Free Anesthesia for Bariatric Surgery (OFA-MG)

July 20, 2025 updated by: HIPÓLITO LABANDEYRA GONZALEZ, Hospital HM Nou Delfos

Comparison of Postoperative Morphine Requirements Between Two Magnesium Sulfate Administration Protocols in Opioid-Free Anesthesia for Bariatric Surgery

This retrospective observational study aims to compare postoperative morphine consumption in patients undergoing bariatric surgery with opioid-free anesthesia (OFA) using two different intravenous magnesium sulfate administration protocols: a single bolus versus a bolus followed by continuous infusion. Medical records of 110 patients operated between June 2022 and December 2023 at Hospital HM Nou Delfos were reviewed. All patients received standardized OFA, and only the magnesium protocol varied between the groups. The primary objective was to evaluate total morphine consumption during the first 48 hours postoperatively. Secondary outcomes included pain scores, antiemetic use, and adverse events. This study was approved by the hospital's Research Ethics Committee (Protocol V3_12.05.2025).

Study Overview

Status

Completed

Conditions

Detailed Description

This is a retrospective, single-center, observational study conducted at Hospital HM Nou Delfos (Barcelona, Spain), which compares the effect of two intravenous magnesium sulfate (MgSO₄) administration protocols on postoperative opioid requirements in patients undergoing bariatric surgery under opioid-free anesthesia (OFA).

The two magnesium protocols evaluated were:

Group A: MgSO₄ bolus 40 mg/kg administered before induction.

Group B: MgSO₄ bolus 50 mg/kg before induction followed by continuous infusion of 15 mg/kg/h until the end of surgery.

All patients underwent standardized OFA including propofol, lidocaine, ketamine and dexmedetomidine. No intraoperative opioids were administered. Multimodal postoperative analgesia was provided in all cases(dexamethasone, paracetamol, and dexketoprofen).

A total of 110 patients were included in the analysis, as defined in the original approved protocol (55 per group).

The primary outcome was cumulative morphine consumption in the first 48 hours postoperatively.

Secondary outcomes included:

Pain scores at rest and with movement at 2, 6, 12, 24, and 48 hours

Use of rescue analgesics

Incidence of postoperative nausea and vomiting (PONV)

Adverse events potentially related to OFA (e.g., hypotension, bradycardia)

Data were extracted from electronic health records and analyzed using descriptive and inferential statistical methods. This study aims to contribute real-world evidence on magnesium strategies in OFA and to support the development of safe, cost-effective analgesic protocols in bariatric patients.

Study Type

Observational

Enrollment (Actual)

110

Contacts and Locations

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

Study Locations

  • Spain
      • Barcelona, Spain, 08023
        • Hospital HM Nou Delfos

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

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Obese adult patients who underwent laparoscopic bariatric surgery under opioid-free total intravenous anesthesia at a single academic center. Participants were retrospectively assigned to one of two magnesium sulfate administration protocols.

Description

Inclusion Criteria:

Age between 18 and 65 years

Body mass index (BMI) ≥ 30 kg/m²

ASA physical status II or III

Underwent laparoscopic bariatric surgery (sleeve gastrectomy or Roux-en-Y gastric bypass) under opioid-free total intravenous anesthesia

Exclusion Criteria:

Pregnancy or breastfeeding

Chronic opioid use before surgery

Known allergy to magnesium sulfate or any drug used in the anesthetic protocol

Severe renal or hepatic insufficiency

Untreated coagulopathy

Active substance abuse

Uncontrolled psychiatric disorders

Intraoperative complications requiring deviation from the protocol

Postoperative morphine consumption exceeding institutional standards

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

Cohorts and Interventions

Group / Cohort
TIVA-OFA Mg Bolus
Patients who received a single IV bolus of magnesium sulfate (40 mg/kg) prior to anesthesia induction, as part of an opioid-free total intravenous anesthesia (TIVA) protocol (propofol, dexmedetomidine, lidocaine, ketamine).
TIVA-OFA Mg Bolus + Infusion
Patients who received a bolus of magnesium sulfate (50 mg/kg) followed by a continuous intraoperative infusion (15 mg/kg/h), as part of an opioid-free TIVA protocol (propofol, dexmedetomidine, lidocaine, ketamine).

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Total postoperative morphine consumption (mg) within 48 hours after surgery
Time Frame: 0-48 hours after surgery
Total amount of morphine administered within 48 hours after surgery, measured in milligrams, as recorded in the post-anesthesia care unit and hospital stay.
0-48 hours after surgery

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of adverse events
Time Frame: Up to 48 hours after surgery
Number of patients experiencing side effects such as nausea, vomiting, pruritus, hypotension, bradycardia, ileus, or urinary retention.
Up to 48 hours after surgery
Pain intensity using Visual Analog Scale (VAS)
Time Frame: 1, 2, 4, 24, and 48 hours postoperatively
Pain intensity assessed using a 10-point Visual Analog Scale (VAS), where 0 represents no pain and 10 represents the worst imaginable pain.
1, 2, 4, 24, and 48 hours postoperatively
Sleep quality reported by the patient
Time Frame: Within 24 hours after surgery
Patient-reported quality of sleep using a numeric scale from 1 (very poor) to 5 (very good).
Within 24 hours after surgery
Patient satisfaction with anesthesia
Time Frame: Within 24 hours after surgery
Satisfaction assessed using a standardized like scale questionnaire (1 = very dissatisfied, 5 = very satisfied).
Within 24 hours after surgery
Length of hospital stay
Time Frame: Up to 5 days after surgery
Total number of days from surgery to discharge, extracted from medical records.
Up to 5 days after surgery

Collaborators and Investigators

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

Sponsor

Hospital HM Nou Delfos

Investigators

  • Principal Investigator: Gregory Contreras-Pérez, Anesthesiologist, Hospital HM Nou Delfos

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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)

June 1, 2022

Primary Completion (Actual)

December 31, 2023

Study Completion (Actual)

January 31, 2024

Study Registration Dates

First Submitted

July 11, 2025

First Submitted That Met QC Criteria

July 20, 2025

First Posted (Actual)

July 22, 2025

Study Record Updates

Last Update Posted (Actual)

July 22, 2025

Last Update Submitted That Met QC Criteria

July 20, 2025

Last Verified

July 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 25.04.2520-GHM

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be shared due to privacy regulations and ethical considerations. The dataset contains sensitive health information from a retrospective analysis and cannot be anonymized to the level required for public release. Access will be limited to the research team and authorized personnel as approved by the ethics committee.

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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