Optimizing the Paracetamol Dose for Prevention of Post-Spinal Shivering in Lower Limb Orthopedic Surgeries

Shivering is a common and distressing complication following spinal anesthesia, affecting up to 70% of patients. It significantly increases oxygen consumption, places stress on the cardiovascular system, and interferes with postoperative monitoring. While intravenous paracetamol has been shown to reduce post-spinal shivering without the sedation or respiratory side effects associated with other medications, existing trials have only investigated a standard 1-gram dose. This study aims to evaluate whether a higher dose of intravenous paracetamol (2 grams) provides superior prevention of post-spinal shivering compared to the standard 1-gram dose and an inactive placebo. Adult patients scheduled for elective lower-limb orthopedic surgery under spinal anesthesia will be randomly allocated to one of three study groups: * High-dose group: intravenous paracetamol 2 g * Standard-dose group: intravenous paracetamol 1 g * Control group: intravenous normal saline placebo Each infusion will be administered over 15 minutes immediately prior to spinal anesthesia. Participants will be observed intraoperatively and for at least 60 minutes in the post-anesthesia care unit (PACU) to measure the incidence and severity of shivering, core body temperature changes, the need for rescue medication, and any adverse events.