A 70 kg, 34-yr old athlete is undergoing emergency laparotomy. Due to non-availability of vecuronium bromide, the surgery was conducted under intermittent doses of succinylcholine (total dose: 640 mg) After surgery, there were no respiratory movements and the patient was unable to move his limbs. What was the cause?

The only depolarizing type of neuromuscular blocker in clinical use is succinylcholine (SCh). Succinylcholine mimics acetylcholine in action and it causes muscle relaxation by causing persistent depolarization of motor end plate. This is also known as phase I blockade. Repeated doses or continuous infusion may cause phase II block. Clinically relevant phase II block can occur with total succinylcholine doses as low as 4 mg/kg in some patients, with either repeat dosing or continuous infusions. Such block may be evident with tetanic stimulation in highly sensitive muscle groups, later respiratory muscles are involved. Patients having abnormal pseudocholinesterase experiences prolonged paralysis after administration of succinylcholine. Ref: Anaesthesia By M. Roy & E.Saha, 2008, Page 28; Surgery: Basic Science and Clinical Evidence By Jeffrey A. Noon, 2008, Page 369.