1) Objectives: The aim of current study is to evaluate Pethidine-sparing effect of intravenous paracetamol and its effect on reducing pain scores after percutaneous nephrolithotomy (PCNL).
2) Design: Randomized double blind controlled trial ( parallel design ) .
3) Setting and conduct: In Hasheminejhad kidney center, our study intervention and placebo will be randomly allocated to the enrolled patients (PCNL cases) using balance blocked randomization.
4) Participants including major eligibility criteria: Enrolled patients will be randomly allocated to 100 placebo and paracetamol groups using balance blocked randomization method (50 patients in each group).inclusion criteria is,Renal calculi candidate for PCNL, Age between 18 -70 years old, American Society of Anesthesiologists (ASA) risk class I (normal healthy patient) and exclusion criteria is, pregnancy and lactation, Drug and alcohol abuse, Previous history of any allergy to acetaminophen and opioid and Bleeding tendency.
5) Intervention: In paracetamol group, each patient will receive 100cc normal saline and 1gr paracetamol intravenously 30 minutes after extubation and then every 8 hours until 24 hours.
In the control group they will received 100cc of normal saline 30 minutes after extubation and every 8 hours for 24 hours (4 times overall).
All patients in both groups will receive 25-50mg intramuscular pethidine, after extubation on the basis of patient demand to the maximum of 200mg/ day.
6) main out come (measures, variables): In both groups, patients pain perception will be recorded using a 100mm visual analog scale (VAS), 30 minutes, one, 4, 8, 12, 16, 20 and 24 hours after extubation. Also pain perception will be recorded on each patient’s demand for rescue opioid analgesic. Ten percent loss to follow up is acceptable.
Primary dependent variable is pain score, and paracetamol dose is independent variable. Pethidine dose received by each patient is considered as the secondary dependent variable.