<prompt> A 70 kg athlete is taken for surgery, due to unavailability of vecuronium, succinylcholine is given repeatedly 640mg. He now is unable to take breath and his lower limbs are paralyzed. What will be cause?Phase II blockSuccinylcholine causes muscle paralysis due to fasciculationHidden muscle dystrophyPseudo cholinesterase deficiency  <response>: Prolonged apnea due to repeated dosing with succinylcholine is due to it entering phase 2 block. Phase I depolarizing block is preceded by muscle fasciculation. During paial neuromuscular block, phase I depolarizing block is characterised by: No fade during repetitive stimulation tetanic or TOF No post tetanic facilitation potentiation Rapid hydrolysis by butyrylcholinesterase plasma cholinesterase terminates phase I depolarizing blockade of succinylcholine. Phase II block resembles non depolarizing block, is characterised by: Fade during repetitive stimulation tetanic or TOF Post tetanic facilitation potentiation Phase II block can be antagonized by administering a cholinesterase inhibitor like neostigmine. 