Clinical Epidemiology Unit, All India Institute of Medical Sciences, New Delhi, India. Electronic address: rawat.dimple96@gmail.com. Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India. Electronic address: roy.avishek1992@gmail.com. Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India. Electronic address: souvikmaitra@live.com. Department of Orthopaedics, All India Institute of Medical Sciences, New Delhi, India. Electronic address: drshankarvivek@gmail.com. Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India. Electronic address: k.punit@yahoo.com. Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India. Electronic address: dalimkumar.ab8@gmail.com.