Which of the following is the best induction agent: September 2009

Ans. D: Thiopentone Thiopental is an ultra-sho-acting barbiturate and has been used commonly in the induction phase of general anaesthesia Following intravenous injection the drug rapidly reaches the brain and causes unconsciousness within 15 seconds. At one minute, the drug attains a peak concentration of about 60% of the total dose in the brain. Thereafter, the drug distributes to the rest of the body and in about 15-20 minutes the concentration is low enough in the brain such that consciousness returns Thiopental is not used to maintain anaesthesia in surgical procedures because, in infusion, it displays zero-order elimination kinetics, leading to a long period before consciousness is regained. Instead, anaesthesia is usually maintained with an inhaled anesthetic (gas) agent. Inhaled anesthetics are eliminated relatively quickly, so that stopping the inhaled anesthetic will allow rapid return of consciousness.