Does Intraoperative Methadone Prevent Postoperative Pain in Bariatric Surgery?

Study Overview
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Brief Summary
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The recent increase in obesity has led to an increase in the need for bariatric surgery. In this group of patients the postoperative pain management is of vital importance. One strategy to improve postoperative analgesia is the use of intraoperative methadone, specially in those patients which regional anesthesia is not feasible. There is evidence that the use of intraoperative methadone can lead to a analgesia lasting 24 to 36 hours, while not associated with increased side effects when compared to other opioids with short or intermediate duration of action. In this study the investigators will evaluate the efficacy of intraoperative methadone in reducing postoperative pain and opioid consumption.

Detailed Description
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Despite recent developments in postoperative pain control, many patients still suffer from moderate to severe pain after surgery. It is estimated that postoperative severe pain occurs in 20 to 40% of surgical procedures. With the recent increase in obesity incidence in the last years, the need for bariatric surgical intervention is greater. The management of postoperative pain in obese patients is particularly important, since this population have increased susceptibility to cardiovascular, pulmonary and thromboembolic perioperatively. One of the strategies to improve pain management in the perioperative period is the intraoperative use of intravenous methadone, given its pharmacokinetic profile, specially in those patients in which regional anesthesia is contraindicated. Methadone is an opioid μ (MOR) receptor agonist, also a glutamate antagonist by blocking the N-methyl-D-aspartate (NMDA) receptor and a reuptake of serotonin and noradrenaline inhibitor. Intraoperative analgesia generated by administration of 20 to 30 mg methadone can last 24 to 36 hours. There is also evidence that methadone at 0.2 to 0.3 mg / kg is not associated with an increased incidence of side effects compared to other opioids with short or intermediate duration of action, such as fentanyl, sufentanyl and morphine. The aim of this study is to evaluate the efficacy of intraoperative methadone in reducing postoperative pain and opioid consumption in patients undergoing open gastroplasty with or without associated Roux Y. Patients will undergo standardized general anesthesia, and the opioid used in anesthesia induction is methadone 0.15 mg / kg fentanyl or 6 mcg / kg bolus with additional if necessary. After extubation a intravenous morphine patient controlled analgesia device will be already available in the operating room. Groups will be compared regarding opioid consumption, pain scores, side effects, patient satisfaction and development of chronic postoperative pain.

Official Title
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Does Intraoperative Methadone Prevent Postoperative Pain in Bariatric Surgery?

Conditions
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Pain, Postoperative, Chronic Pain

Intervention / Treatment
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* Drug: Use of Intraoperative Intravenous Methadone
* Drug: Use of Intraoperative Intravenous Fentanyl


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Open bariatric surgery No contraindications for any drugs used during the trial Read, understood and signed the informed consent Exclusion Criteria: Laparoscopic bariatric surgery Known allergy to any drugs used during the trial Cardiovascular disease Creatinine clearance lower than 60 mL/min/1.73 m2 Chronic usage of opioids History of personality disorder

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Methadone<br>Methadone used as anesthesia opioid: induction with 0,15 mg / kg intravenous methadone. Boluses of 0,05 mg / kg intravenous methadone as needed intraoperatively | Drug: Use of Intraoperative Intravenous Methadone<br>* The intervention group will be given intravenous methadone at a fixed induction dose (0,15 mg / kg) and intraoperative boluses as judged necessary by the anesthesiologist<br>* Other names: Methadone;|
| Active Comparator: Fentanyl<br>Fentanyl used as anesthesia opioid: induction with 6 mcg / kg intravenous fentanyl. Boluses of 2 mug / kg intravenous fentanyl as needed intraoperatively | Drug: Use of Intraoperative Intravenous Fentanyl<br>* The active control group will be given intravenous fentanyl at a fixed induction dose (6 mg / kg) and intraoperative boluses as judged necessary by the anesthesiologist<br>* Other names: Methadone;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative Pain | Postoperative pain will be evaluated using a verbal numerical pain scale (ranging from 0 to 10) | Until 3 months postoperatively | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative opioid consumption | Postoperative opioid consumption will be evaluated at fixed postoperative times: 2h, 6h, 24h, 48h, 72h and 3 months | Until 3 months postoperatively | 
| Side effects | Nausea, vomiting, itching, urinary retention, respiratory depression, sedation will be evaluated at fixed postoperative times: 2h, 6h, 24h, 48h, 72h and 3 months | Until 3 months postoperatively | 
| Chronic postoperative pain | Patients will be evaluated for chronic pain 3 months postoperatively through a questionnaire which includes questions about numerical verbal scale of pain in the last three months, analgesic consumption and satisfaction with analgesia regimen | 3 months postoperatively | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Methadone, Pain, Postoperative, Chronic Pain, Bariatric Surgery