Ahmad Muhammad Taha1,2, Nader Darwich3. 1. Department of Anesthesia, Healthpoint Hospital, Abu Dhabi, UAE. ahmadtaha_1@yahoo.com. 2. Department of Anesthesia, Ain Shams University, Cairo, Egypt. ahmadtaha_1@yahoo.com. 3. Department of Orthopaedics, Healthpoint Hospital, Abu Dhabi, UAE.