Novel Device for Small Animal Anesthesia

Heterotopic intestinal transplantation in the rat is an effective model of transplant rejection and graft-versus-host disease. Animal loss from anesthesia complications can result in loss of experimental time and money, and poorly reproducible results. We evaluated injectable anesthetic agents, including chloral hydrate, ketamine, and pentobarbital for use in this procedure, but the level of anesthesia, including under- and overdosage, remained a problem. An induction system using inhaled halothane, nitrous oxide, and oxygen has proven to give consistent results. The animal is immersed in a chamber prefilled with the gas mixture. After achievement of anesthesia, the animal is removed and placed on an open anesthesia circuit. This circuit is composed of a specially designed plexiglass nose cone with a dual chamber - an inner chamber for gas administration and an outer chamber for fume removal. Anesthesia is then adjusted on the basis of respiratory rate, and can be adjusted on the basis of physiologic status of the animal. Anesthesia is gradually terminated approximately two minutes prior to completion of surgery, and the animal is resuscitated, using oxygen at low flow rates. This results in over 95% spontaneous awakening with no residual anesthesia. We believe that this novel anesthetic delivery system is useful not only for transplantation in rats, but also for other small animal surgery requiring prolonged anesthesia.