Comparison of Local Lidocaine Infiltration, Intramuscular Morphine, and Placebo for Postoperative Pain Control After Percutaneous Nephrolithotomy (PCNL): A Double-Blind Randomized Controlled Trial

Comparison of the effect of local lidocaine infiltration, intramuscular morphine, and placebo on pain control and reduction of opioid analgesic consumption after PCNL in patients receiving a standard analgesic regimen.

Phase III, double‑blind, parallel‑group, three‑arm (local lidocaine, intramuscular morphine, placebo) randomized controlled trial with 60 patients. Block randomization (block size 6) was performed using SPSS software. Allocation concealment was ensured using sequentially numbered, opaque, sealed envelopes. All patients received a standard baseline analgesic regimen.

Urology Dept., Shahid Beheshti Hosp., Hamadan, Iran. Mar–Sep 2026. Consecutive elective PCNL patients randomized to three groups. Patient, outcome assessor, analyst blinded (double‑blind via third‑party nurse). Interventions at surgery end; 48h follow‑up.nts were followed for 48 hours postoperatively.

Adult patients (≥18 years) of both sexes scheduled for elective standard PCNL with ASA physical status I-III; no chronic opioid use; non-pregnant and non-lactating women. Exclusion criteria: allergy to lidocaine or morphine; coagulopathy; active untreated urinary tract infection (positive culture); severe obesity (BMI ≥40 kg/m²); need for multiple tracts or simultaneous double-J stent; history of open renal surgery or previous PCNL on the same kidney; abnormal renal anatomy; conversion to open surgery or intra‑operative emergency; significant bleeding requiring transfusion; need for postoperative ICU admission.

Group A: 20mL 2% lidocaine (4mg/kg) locally + standard regimen. Group B: 5mg IM morphine + standard regimen. Group C: 20mL normal saline locally + standard regimen

VAS score at 6,12,24,48h; total rescue pethidine at 48h; time to first analgesic request.

To generate the random allocation sequence, SPSS version 26 was used. First, under the Transform menu, Random Number Generators was selected, and the Uniform method was set with a fixed seed of 20260321. Then, using the Compute Variable command, a uniform random variable ranging from 0 to 1 was created. After sorting cases by this random variable, blocks of size 6 were formed. Within each block of 6, 2 patients were randomly assigned to group A (local lidocaine), 2 to group B (intramuscular morphine), and 2 to group C (placebo). The final sequence consisted of a list of group codes (A, B, C) for 60 patients (20 blocks of 6). This sequence was printed on paper and placed into sequentially numbered, opaque, sealed envelopes. A nurse who was not involved in patient assessment opened the envelopes in numerical order and, based on the code inside, prepared the study drug or placebo in identical syringes. Neither the patient nor the outcome assessor was aware of the group code. No stratification was used.

In this double‑blind trial, the participants (patients), the outcome assessor (anesthesiology resident) , and the data analyst were blinded to group allocation. Patients were unaware of the intervention they received. Study medications (lidocaine, morphine, and normal saline) were prepared by a nurse who was not involved in patient assessment, using identical syringes labeled only with a group code (A, B, or C). The surgeon (principal investigator) could not be blinded to the nature of the intervention because of the different routes of administration (local injection in groups A and C versus intramuscular injection in group B). However, he was also unaware of the syringe content in groups A and C (both injected locally). The anesthesiology resident who assessed pain using the Visual Analogue Scale (VAS) at 6, 12, 24, and 48 hours postoperatively had no knowledge of group assignment. Likewise, the data analyst received data coded by group letter (A, B, or C) only, with no information about the actual intervention, ensuring blinding during the analysis. No Data Safety and Monitoring Committee was involved in this study.

Individual raw data will not be published due to confidentiality and lack of prior plans for public sharing.

Full study protocol (including background, objectives, methodology, inclusion/exclusion criteria, interventions, outcomes, statistical analysis plan, and ethical considerations). The protocol is summarized in the IRCT registry and the full document will be provided upon request by the journal or researchers.

From the time of acceptance of the main article by the journal (estimated about 6 months after trial registration) for a period of 5 years.

Researchers working in academic and scientific institutions (after submitting a written request and signing a non‑commercial use agreement).

Solely for reproducing results, conducting meta‑analyses, or examining methodology. Commercial use is prohibited. Requests must be justified with a clear purpose.

Corresponding author (Dr. Reza Shamsollahi) via email: r.sh.1376@gmail.com

Requests will be reviewed by the corresponding author within a maximum of 30 days. If approved, the protocol file (PDF) will be sent via email.