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Comparison of Opioid-Free versus Opioid-Based General Anesthesia for Reducing Nausea and Vomiting After Robotic Bariatric Surgery in Obese Patients (ANGELO Study)

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on obesity in patients undergoing robotic bariatric surgery (surgical procedures performed with robotic assistance to help reduce body weight). The purpose is to determine whether opioid-free general anesthesia reduces the frequency and intensity of postoperative nausea and vomiting compared to opioid-based general anesthesia. General anesthesia is medication that puts patients into a sleep-like state during surgery, while opioids are strong pain medications that can sometimes cause side effects like nausea and vomiting.

During the study, participants will be given either a type of general anesthesia that contains no opioid medications or the standard anesthesia that includes opioids. After surgery, researchers will monitor how much nausea and vomiting patients experience, along with their pain levels and need for additional pain medication during the first 24 hours following surgery.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Assignment to a study group

    You will be randomly assigned to one of two anesthesia groups for your robotic bariatric (weight loss) surgery: either opioid-free general anesthesia or opioid-based general anesthesia.

    This study aims to determine if opioid-free anesthesia reduces postoperative nausea and vomiting compared to traditional opioid-based anesthesia.

  2. Step 2

    Receiving anesthesia during surgery

    If you are in the opioid-free group, you will receive a combination of medications that may include magnesium sulfate, lidocaine hydrochloride, dexmedetomidine, and ketamine hydrochloride.

    If you are in the opioid-based group, you will receive standard anesthesia medications which include opioid pain medications.

    The anesthesiologist will administer these medications through an IV line while you are unconscious during your bariatric surgery.

  3. Step 3

    Postoperative assessment period

    After your surgery, you will be monitored for 24 hours to assess how you're feeling.

    You will be asked to rate your nausea using a Visual Analog Scale for Nausea (VAS-N), which is a simple line where you mark your level of nausea from none to severe.

    You will also rate your pain using a similar Visual Analog Scale for Pain (VAS-P).

    The medical team will record if and when you request any additional pain medication (opioids) during this 24-hour period.

  4. Step 4

    Study completion

    Your participation in the study will end after the 24-hour monitoring period following your surgery.

    The information collected about your nausea, pain levels, and medication needs will be used to help determine which anesthesia approach might be better for future patients undergoing similar surgeries.

Who can join the trial?

6 criteria

  • You must be scheduled for bariatric surgery (weight loss surgery)
  • You must be between 18 and 75 years old
  • You must be voluntarily choosing to have the surgery (not emergency surgery)
  • You must be classified as ASA I-III (a health classification system where I means healthy, II means mild disease, and III means severe but not incapacitating disease)
  • You must be willing to sign an informed consent document
  • Both men and women can participate

Who cannot join the trial?

11 criteria

  • If you have a known hypersensitivity (severe allergic reaction) to any of the study medications
  • If you are under 18 years of age
  • If you are currently pregnant or breastfeeding
  • If you have severe heart problems that would make surgery risky
  • If you have severe liver disease that affects how your body processes medications
  • If you have severe kidney disease that affects how your body eliminates medications
  • If you have a history of chronic pain requiring regular opioid medication use
  • If you have uncontrolled high blood pressure that could increase surgical risks
  • If you have a history of adverse reactions to anesthesia in previous surgeries
  • If you are unable to provide informed consent due to cognitive issues or language barriers
  • If you are currently participating in another clinical trial that might interfere with this study
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Investigated drugs

  • Opioid-Free General Anesthesia

    is a type of anesthesia technique that uses various non-opioid medications to keep patients comfortable and pain-free during surgery without using opioid painkillers. This approach aims to provide effective pain control while avoiding the side effects commonly associated with opioids, such as nausea and vomiting.

  • Opioid-Based General Anesthesia

    is the traditional approach to anesthesia that includes opioid medications (like fentanyl or morphine) as part of the pain management strategy during surgery. Opioids are powerful pain relievers commonly used during surgical procedures, but they can cause side effects such as postoperative nausea and vomiting.

What is already known about the treatment

  • Propofol

    An intravenous anesthetic agent commonly used for the induction and maintenance of general anesthesia during surgical procedures, including bariatric surgery. It works by enhancing the inhibitory effects of gamma-aminobutyric acid (GABA) in the brain, resulting in sedation and loss of consciousness. Propofol belongs to the class of drugs known as sedative-hypnotics and is favored for its rapid onset, short duration of action, and reduced incidence of postoperative nausea and vomiting compared to other anesthetics, making it particularly valuable in bariatric surgery where patients may already have a higher risk of these complications.

  • Sevoflurane

    An inhaled anesthetic gas administered through a breathing circuit during surgery to maintain general anesthesia after induction. It works by altering nerve transmission in the brain by enhancing inhibitory function and decreasing excitatory transmission, leading to unconsciousness, amnesia, and immobility. Sevoflurane belongs to the halogenated ether group of general anesthetics and is widely used due to its pleasant smell, rapid onset and offset, and good safety profile with minimal effects on heart rate and blood pressure, making it suitable for various surgical procedures including bariatric surgery.

  • Dexmedetomidine

    An intravenous medication administered during surgery that provides sedation, anxiety reduction, and pain relief without significant respiratory depression. It works by stimulating alpha-2 adrenergic receptors in the brain and spinal cord, reducing the release of norepinephrine and decreasing sympathetic nervous system activity. Classified as an alpha-2 adrenergic agonist, dexmedetomidine is increasingly used in opioid-free anesthesia protocols to reduce opioid requirements, decrease postoperative nausea and vomiting, and provide more stable hemodynamics during procedures like bariatric surgery.

  • Ketamine

    An intravenous anesthetic agent used in low doses during surgery to provide pain relief and reduce the need for opioids. It works differently from most anesthetics by blocking NMDA receptors in the brain, producing dissociative anesthesia along with analgesic effects. Classified as a dissociative anesthetic and NMDA receptor antagonist, ketamine has gained popularity in multimodal and opioid-free anesthesia protocols for its ability to reduce postoperative pain, decrease opioid consumption, and potentially reduce the incidence of chronic pain after surgery, making it valuable in procedures like bariatric surgery.

  • Lidocaine

    An intravenous medication administered during surgery to reduce pain and decrease the need for other pain medications. It works by blocking sodium channels in nerve cells, preventing the generation and conduction of pain signals throughout the body. Classified as an amide-type local anesthetic, intravenous lidocaine has gained popularity in enhanced recovery protocols and opioid-free anesthesia due to its analgesic, anti-inflammatory, and anti-hyperalgesic properties, along with its ability to reduce postoperative ileus and potentially decrease nausea and vomiting after procedures like bariatric surgery.

  • Magnesium sulfate

    An intravenous medication given during surgery to provide pain relief, reduce muscle spasms, and decrease the need for opioids. It works by blocking NMDA receptors and calcium channels, resulting in reduced pain signal transmission and muscle relaxation. Classified as an electrolyte supplement and NMDA receptor antagonist, magnesium sulfate has become an important component in multimodal and opioid-free anesthesia regimens due to its analgesic, anti-inflammatory, and neuroprotective properties, as well as its potential to reduce postoperative pain and opioid requirements after procedures like bariatric surgery.

Investigated diseases

Obesity – A chronic medical condition characterized by excessive accumulation of body fat to the extent that it may have negative effects on health. It occurs when a person's body mass index (BMI) exceeds 30 kg/m². Obesity develops when energy intake consistently exceeds energy expenditure, leading to storage of excess calories as fat. This condition is associated with metabolic changes and can affect multiple body systems. Obesity increases the mechanical load on the body and alters normal physiology. Over time, it can lead to various complications including cardiovascular issues, insulin resistance, and joint problems.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-521047-20-00Protocol codeANGELOEstimated enrolment64 patientsSponsorInstitut De Recerca Biomedica De Lleida Fundacio Dr. Pifarre

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