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NCT Number: NCT07337135

Opioid-Free vs Opioid-Based Anesthesia in Bariatric Surgery

This prospective randomized controlled trial aims to compare the clinical effectiveness and safety of opioid-free anesthesia (OFA) versus traditional opioid-based anesthesia (OBA) in adult patients undergoing laparoscopic bariatric surgery. The study evaluates postoperative pain, need for rescue analgesia, incidence of postoperative nausea and vomiting (PONV), intraoperative nociception monitoring (NOL index), and patient satisfaction. A total of 60 patients were randomized into two parallel groups receiving either OFA or OBA according to standardized anesthetic protocols.

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Key information

Conditions

Morbid Obesity Bariatric Surgery Body Weight Nausea Neurologic Manifestations Nutrition Disorders Nutritional and Metabolic Diseases Obesity Obesity, Morbid Opioid Free Anesthesia Overnutrition Overweight Pain Pain, Postoperative Pathologic Processes Pathological Conditions, Signs and Symptoms Postoperative Complications Postoperative Pain Signs and Symptoms Signs and Symptoms, Digestive Vomiting

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Hospital Lusíadas Amadora - Lusíadas Saúde, S.A.

Amadora, 2724-002, Portugal

About this study

Bariatric surgery is the most effective treatment for severe and morbid obesity, but perioperative pain management and PONV remain significant challenges. Traditional opioid-based anesthesia is associated with adverse effects such as respiratory depression, postoperative hyperalgesia, ileus, and delayed recovery.

Opioid-free anesthesia is an emerging strategy based on the use of multimodal, non-opioid agents-including dexmedetomidine, lidocaine, and ketamine-aimed at providing adequate analgesia while reducing opioid-related complications.

This randomized controlled trial evaluates whether OFA improves postoperative pain control, reduces the requirement for rescue analgesia, and promotes better perioperative outcomes compared to OBA in laparoscopic bariatric surgery. Outcomes include NRS pain scores at multiple time points, NOL monitoring during surgery, PONV occurrence, and patient satisfaction at discharge.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥ 18 years;
  • Body mass index (BMI ≥ 35 kg/m² with associated comorbidities) or BMI ≥ 40 kg/m²;
  • Scheduled for elective laparoscopic bariatric surgery;
  • Ability to provide informed consent.

Exclusion criteria

  • Pregnancy;
  • History of substance abuse;
  • Severe psychiatric disease;
  • Contraindications to any of the drugs used in either anesthetic protocol (dexmedetomidine, ketamine, lidocaine, remifentanil, etc.);
  • Inability to comply with study procedures;
  • Refusal or inability to provide informed consent.

Treatment and study plan

Opioid-Based Anesthesia (Remifentanil-Based Protocol)

Drug

Participants receive standard opioid-based general anesthesia consisting of:

  • Continuous remifentanil infusion (2 mg diluted in 40 mL saline),
  • Propofol for induction,
  • Rocuronium for neuromuscular blockade,
  • Desflurane for maintenance,
  • Dexamethasone 4-8 mg for PONV prophylaxis,
  • Cefazolin for antibiotic prophylaxis,
  • Esomeprazole for stress-ulcer prevention.

Postoperative analgesia includes paracetamol + ketorolac/parecoxib + metamizole, with tramadol and/or morphine provided as rescue. NOL, BIS, TOF, and standard monitoring are used.

Opioid-Free Anesthesia (Dexmedetomidine-Ketamine-Lidocaine Protocol)

Drug

Participants receive opioid-free anesthesia consisting of:

  • Dexmedetomidine bolus (15-20 μg),
  • Continuous infusion of dexmedetomidine 50 μg + ketamine 50 mg + lidocaine 500 mg in 50 mL saline (rate: 1 mL/10 kg),
  • Propofol for induction,
  • Rocuronium for neuromuscular blockade,
  • Desflurane for maintenance,
  • Dexamethasone for PONV prophylaxis,
  • Cefazolin and esomeprazole for prophylaxis.
  • The analgesic infusion is reduced by half 30 min before end of surgery and continued for 1 hour in PACU.

Postoperative analgesia includes paracetamol + ketorolac/parecoxib + metamizole, with tramadol 100 mg as rescue. Monitoring includes NOL, BIS, TOF.

Primary outcomes

  1. Postoperative Pain Intensity Measured by the Numerical Rating Scale for Pain (NRS)

    Time frame: Time Frame: - Within 30 minutes of arrival at the Post-Anesthesia Care Unit (PACU); - At PACU discharge (assessed up to 2 hours after PACU admission); - Within the first 24 postoperative hours; - 48 hours postoperatively (at hospital discharge).

    Postoperative pain will be assessed using the Numerical Rating Scale for Pain (NRS), a validated 11-point scale ranging from 0 (no pain) to 10 (worst pain imaginable). Higher scores indicate a worse outcome, reflecting greater pain intensity.

    Pain intensity will be compared between the opioid-free anesthesia group and the opioid-based anesthesia group at predefined postoperative time points.

Secondary outcomes

  1. Intraoperative Nociception (NOL Index)

    Time frame: Multiple standardized time points during surgery (15 to 180 minutes)

    Nociception will be assessed using the NOL (Nociception Level) Index, a multiparametric autonomic signal-based monitor. Lower values reflect better nociceptive control. Comparisons will be made between OFA and OBA groups at all recorded time points.

  2. Need for Rescue Analgesia

    Time frame: - During PACU stay (assessed up to 2 hours after PACU admission).

    The proportion of patients requiring rescue analgesia (tramadol and/or morphine) will be compared between the opioid-free anesthesia group and the opioid-based anesthesia group.

  3. Opioid Consumption

    Time frame: - During PACU stay (assessed up to 2 hours after PACU admission).

    Need for opioid administration as rescue analgesia will be recorded and compared between groups.

  4. Incidence of Postoperative Nausea and Vomiting (PONV)

    Time frame: At 6 hours and 24 hours after surgery

    PONV will be assessed using the Postoperative Nausea and Vomiting Impact Scale, comparing frequency and severity between groups. The total score ranges from 0 (no nausea or vomiting) to 6 (maximum impact). Higher scores indicate a worse outcome, reflecting greater severity and clinical impact of postoperative nausea and vomiting.

  5. Need for PONV Treatment

    Time frame: First 24 postoperative hours

    Proportion of patients requiring antiemetic treatment will be evaluated and compared.

  6. Patient Satisfaction

    Time frame: 48 hours postoperatively (at hospital discharge).

    Patient satisfaction will be assessed using a Numerical Satisfaction Rating Scale and compared between groups. Total score ranges from 1 (minimum satisfaction) to 10 (maximum satisfaction). Higher scores indicate a better outcome, reflecting greater patient satisfaction.

  7. Postoperative Complications

    Time frame: Periprocedurally, up to 48 hours postoperatively.

    Occurrence of perioperative complications (respiratory, cardiovascular, surgical, or anesthesia-related) will be recorded.

Sponsors and collaborators

Lead sponsor

Hospital dos Lusíadas

Other

Registry information

Official study title

Opioid-free Anesthesia vs Opioid-based Anesthesia / A Heavyweight Showdown - Randomized Controlled Trial

Important dates

Study start
2023
Primary completion
2024
Study completion
2024
First posted
Jan 13, 2026
Registry last updated
Feb 25, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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