<prompt> A 70 year old patient with benign prostatic hyperplasia underwent transuretheral resection of prostate under spinal anaesthesia. One hour later, he developed vomiting and altered sensorium. The most probable cause is ?Over dosage of spinal anaesthetic agentRupture of bladderHyperkalemiaWater intoxication  <response>: Ans. is d i.e., Water intoxication 