[Programmed injection of liquid volatile anesthetics into the system. A plea for a tightly closed circuit]

Severinghaus et Lowe have given us a precise means of knowing what the patient's anaesthetic needs are under volatile anaesthesia. The parameters of the well-known formula for calculating the unit dose, Qan = 2 [Qc (dl).lambda.1.3 MAC], are recorded in the microprocessor of a computerized syringe: 1) the patient's body weight to the power 0.75 and multiplied by 2, i.e. cardiac output (Qc); 2) the nature of the selected volatile, i.e. the product of elements other than the Qc. The microprocessor calculates also the rate per minute according to the information obtained from the clock and the principle that the rate of anaesthetic is inversely proportional to the square root of the time the anaesthesia lasts. A numerical panel gives information on the following: injection time, injected anaesthetic volume per minute, cumulative quantity of liquid anaesthetic injected. The syringe is set in such a manner as to face upwards to prevent the development of bubbles. A rapidly stable alveolar concentration is obtained, proving Lowe right.