Investigating the Efficacy of Local Injection of Ropivacaine on Postoperative Pain in Patients Undergoing Kocher's Incision: A Randomized Clinical Trial

To evaluate the efficacy of local ropivacaine injection at the surgical incision site in reducing postoperative pain in patients undergoing surgery with Kocher's incision.

Randomised, parallel group, double-blind, controlled clinical trial, phase 3, conducted on 48 patients.

The study will be conducted in Madani Hospital. Eligible patients will be randomly assigned to two groups after obtaining informed consent. Drug injection will be performed by the surgeon without the knowledge of the patient or the data collector. Double-blind design is maintained.

Participants aged 18 to 65 years with a body weight between 45 and 100 kg, ASA class I or II, and candidates for Kocher’s incision surgery will be included; patients with known allergy to local anesthetics, severe cardiovascular, renal, or hepatic disease, history of substance abuse, or ASA class greater than II will be excluded.

The intervention group will receive 20 mL of 5 mg/mL ropivacaine subcutaneously at the Kocher’s incision site at the end of surgery. The control group will receive 20 mL of 0.9% normal saline in the same manner.

Postoperative pain score measured by VAS at 2, 4, 8, 12, and 24 hours after surgery; time to first rescue analgesic administration; total dose of rescue analgesics within 24 hours.

A block randomization method with a block size of 4 and a 1:1 allocation ratio was used to assign participants to either the intervention (ropivacaine) or control (normal saline) group. The randomization list was generated using Random Allocation Software by an independent statistician who was not involved in the recruitment, intervention, or outcome assessment. To ensure balanced group sizes over time, random permutations of block sequences (e.g., AABB, ABAB, BBAA, etc.) were used. Each allocation code was sealed in an opaque, sealed, and sequentially numbered envelope. These envelopes were prepared by a third party blinded to the study objectives and group assignments. Upon enrollment and informed consent, the operating room nurse opened the next envelope in sequence to determine the assigned intervention, which was then administered accordingly.

This study was conducted in a double-blind manner, meaning that both the patients and the outcome assessor were blinded to group allocation. Ropivacaine and placebo (0.9% normal saline) solutions were indistinguishable in volume, color, and appearance. The study medications were prepared in identical, unlabeled syringes by a third party not involved in the trial. Each syringe was marked with a code and administered by an anesthetic nurse or operating room staff unaware of the allocation at the end of the procedure. Postoperative pain assessment was performed by a nurse blinded to the treatment group. Group assignments were concealed until data analysis was complete.

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