The goal of this randomized clinical trial is to find out whether giving an intravenous lidocaine + dexmedetomidine combination (LIDEX) during laparoscopic bariatric surgery can lower post-operative pain, inflammation, and oxidative stress in adults with obesity.
The main questions it aims to answer are:
* Pain control: Does LIDEX reduce pain 24 hours after surgery, as measured with the International Pain Outcomes Questionnaire (IPOQ)? * Biomarkers: Does LIDEX lower blood levels of key inflammatory cytokines-interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-10 (IL-10)-and oxidative-stress markers-malondialdehyde (MDA), the reduced/oxidized glutathione ratio (GSH/GSSG), superoxide dismutase (SOD), and catalase-compared with the individual drugs or saline placebo?
Researchers will compare four groups: lidocaine alone, dexmedetomidine alone, LIDEX, and placebo (saline solution, a look-alike substance that contains no drug) to learn which approach works best.
Participants will:
* Receive an intravenous infusion of their assigned study drug(s) during surgery. * Provide three small blood samples (before surgery, immediately after, and three hours after). * Complete a short pain questionnaire (IPOQ) 24 hours after surgery.
Adults aged 18 - 60 years
Male or female
Elective laparoscopic bariatric surgery
Post-operative pathway: post-anaesthesia care unit (PACU) followed by standard ward, with an expected in-hospital stay ≥ 24 h
Use of any loco-regional anaesthetic technique during the peri-operative period (transversus abdominis plane, paravertebral, spinal, epidural, erector spinae, or other abdominal wall blocks).
Current substance abuse or illicit drug use.
Previous abdominal surgery within the last 6 months.
Known hypersensitivity or allergy to lidocaine, dexmedetomidine, amide local anaesthetics, or α₂-adrenergic agonists.
Parallel
Intravenous Lidocaine infusion + Standard Anesthesia
DrugContinuous IV infusion of lidocaine 1 % (10 mg mL-¹) at 0.3 mL kg-¹ h-¹ (≈ 1.5 mg kg-¹ h-¹) from induction of anaesthesia to skin closure. No loading bolus, no post-operative infusion.
Intravenous Dexmedetomidine infusion + Standard Anesthesia
DrugContinuous IV infusion of dexmedetomidine 1 µg mL-¹ at 0.3 mL kg-¹ h-¹ (≈ 0.3 µg kg-¹ h-¹) without loading dose, started after induction and stopped at skin closure. No post-operative infusion.
Lidocaine + Dexmedetomidine Combination (LIDEX) + Standard Anesthesia
DrugSingle syringe containing lidocaine 1 % (10 mg mL-¹) + dexmedetomidine 1 µg mL-¹, infused IV at 0.3 mL kg-¹ h-¹ (delivering ≈ 1.5 mg kg-¹ h-¹ lidocaine + 0.3 µg kg-¹ h-¹ dexmedetomidine) from induction to skin closure.
0.9 % Saline Placebo + Standard Anesthesia
DrugVolume-matched IV infusion of 0.9 % normal saline at 0.3 mL kg-¹ h-¹ for the same duration and through the same delivery line as active arms; identical syringe appearance.
Assessment of postoperative pain patient perception using the Spanish International Pain Outcomes Questionnaire (IPOQ). This questionnaire includes multiple items assessed on a numerical rating scale (NRS) from 0 to 10.
* For most items (e.g., pain intensity, interference with activities, emotional impact), \*\*higher scores indicate worse outcomes\*\*. * For items such as pain relief and satisfaction, \*\*higher scores indicate better outcomes\*\*. Items include: * Highest and lowest pain intensity experienced since surgery * Proportion of time spent in pain * How pain limited physical activities (e.g., coughing, moving, walking) * Impact of pain on mood and emotional well-being * Adverse effects attributed to pain medication (e.g., nausea, dizziness) * Overall degree of pain relief obtained * Desire for additional analgesic treatment * Clarity and usefulness of information received about pain therapy * Extent of patient involvement in treatment decisions * Global satisfaction with pain management * Use of non-pharmacological methods for pain relief * Presence of pre-existing pain before hospital admission
Change in pro-inflammatory cytokine (IL-1β, IL-6, TNF-α) and anti -inflammatory IL-10 panel
Serum concentrations of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α) measured by multiplex ELISA (pg mL-¹). The primary comparison is the change from baseline and the area-under-curve (AUC₀-₃ h) across the four treatment arms; lower values indicate a reduced systemic inflammatory response.
Change in oxidative-stress marker panel (MDA, GSH/GSSG ratio, SOD, catalase, neutrophil respiratory burst)
Plasma malondialdehyde (MDA, µmol L-¹; TBARS assay), glutathione redox ratio (GSH/GSSG), superoxide-dismutase activity (SOD, U mL-¹) and catalase activity (U mL-¹) will be quantified with spectrophotometric/enzymatic methods. Neutrophil respiratory burst (reactive oxygen-species production) will be assessed by flow cytometry using DCFH-DA and expressed as mean fluorescence intensity (MFI). Change from baseline and the area-under-the-curve (AUC₀-3 h) will be compared across the four study arms; lower MDA/MFI and higher antioxidant indices indicate less oxidative stress.
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