<prompt> Which intravenous anaesthetic can be used for upper airway manipulation in absence of neuromuscular blockers-ThiopentonePropofolEtomidateKetamine  <response>: Propofol - induced depression of upper airway reflexes exceeds that of any other agent thus allowing intubation, endoscopy or laryngeal mark placement in absence of neuromuscular blockers. ketamine preserve upper airway reflexes. 