Abstract
During closed-circuit anesthesia, an inhalational anesthetic has traditionally been administered by injecting a liquid agent directly into the anesthetic circuit using a syringe. This bolus injection method causes wide fluctuations in anesthetic concentration, which frequently leads to undesirable hemodynamic instability. To overcome this problem, we devised a new inhalational anesthetic vaporizer, which combines a continuous infusion pump with an in-circuit vaporizing chamber. The vaporizing chamber, with a heater incorporated to facilitate vaporization of the inhalational agent, is attached to the expiratory limb of the anesthesia circuit. The inhalational anesthetic of choice is continuously delivered in liquid form to this chamber by an infusion pump, and the rate of infusion can be adjusted by an anesthetist. We used this devise for clinical cases of closed circuit anesthesia and found that it could respond promptly to changes in anesthetic requirements during induction and periods of intense stimuli, while providing a smooth course for maintenance. In conclusion, this new vaporizer makes closed circuit anesthesia easier and safer.
