Functional Endoscopic Sinus Surgery (FESS) is a commonly performed procedure where a bloodless surgical field is critical for success. Controlled hypotensive anaesthesia is often used to minimize intraoperative bleeding and improve visualization. Dexmedetomidine, a selective alpha 2 adrenergic agonist, is widely employed for this purpose due to its sedative, analgesic, and sympatholytic properties. However, the optimal bolus dose for achieving effective hypotension with minimal adverse effects remains unclear.

This prospective, randomized, double blind, active controlled study aims to compare the efficacy and safety of two different bolus doses of intravenous dexmedetomidine, 0.25 microgram per kilogram and 0.5 microgram per kilogram, administered over 30 minutes after induction of general anaesthesia in patients undergoing elective FESS. Sixty patients aged 18 to 65 years, ASA physical status I or II, will be randomly allocated into two groups of 30 each using computer generated randomization with allocation concealment.

The primary outcome will be the proportion of intraoperative mean arterial pressure readings within the target range, defined as 55 to 65 mmHg for non hypertensive patients, or 15 to 20 percent below baseline mean arterial pressure for controlled hypertensives. Secondary outcomes will include postoperative sedation assessed by Ramsay Sedation Score, and incidence of adverse events such as hypotension and bradycardia.

The study seeks to determine whether either of the two lower bolus doses of dexmedetomidine, 0.25 or 0.5 microgram per kilogram, is sufficient to achieve controlled hypotension during FESS with fewer adverse effects when compared to higher doses reported in previous studies.