This randomized controlled trial assessed whether intravenous ondansetron is more effective than low dose ketamine in preventing shivering after spinal anesthesia in adults undergoing elective surgery. Post spinal shivering is a frequent and uncomfortable complication of spinal anesthesia and may increase oxygen demand and interfere with routine monitoring. Adults aged 20 to 70 years (body weight 50 to 80 kg; American Society of Anesthesiologists class I to II) scheduled for elective procedures under standardized spinal anesthesia were randomly allocated in equal numbers to receive either ondansetron 8 mg intravenously or ketamine 0.25 mg/kg intravenously, administered 5 minutes after the spinal injection. Perioperative temperature management was standardized for all participants. The primary outcome was the occurrence of post spinal shivering during intraoperative monitoring. Among 180 participants, shivering occurred in 30.0% of those receiving ondansetron and 44.4% of those receiving ketamine, showing a statistically significant reduction with ondansetron.

Inclusion Criteria:

• Patients of either gender aged 20-60 years with ideal body
• weight of 50 to 80 kg.
• Patients meeting ASA classification I and II determined by
• anesthesiologist.
• Patients undergoing elective surgeries under spinal anesthesia.
• Duration of surgery should not be more than 3 hours.

Exclusion Criteria:

• Patients having a documented history of severe adverse reactions to ketamine or ondansetron.
• Patients with cardiovascular disease documented in history.
• Patients with hepatic disease documented in history and supported by lab results (AST 32-40U/L), ALT(10-40U/L).
• Patients with renal disease documented in history and supported by lab results. Urea (10-50mg/dl) S/Creatinine (0.3-1.5mg/dl).
• Patients with hyperthyroidism documented in history and supported by lab results.
• Patients with history of mental illness, seizures and glaucoma.
• Patients with known hypertension (BP greater than 140/90).
• Haemodynamically unstable patients (BP<100mmHg).
• Patients with coagulopathy or other bleeding diathesis documented in history and supported by lab results.
• Complicated prolonged surgeries in spinal anesthesia.