Pupillary Reactions During Ether and Chloroform Anesthesia After Morphine.

In the course of anesthesia by ether and chloroform in the dog, the pupil dilates at 2 stages, in the period of excitement and in the period of deep narcosis. If there is violent excitement the intermediary constriction is not observed. It is commonly held that the primary dilatation is a reflex phenomenon (inhibition of the oculomotor or stimulation of the sympathetic or both). There is no clear statement, however, whether the dilatation of the pupil in the stage of deep narcosis is the result of asphyxia or the direct effect of the anesthetic. While studying the response of the vagus nerve to morphine during ether and chloroform anesthesia, it was observed that in deep ether narcosis, the pupils of the dog under the influence of morphine were widely dilated, while in deep chloroform narcosis under the same conditions, the pupils were constricted. These observations seemed of interest in their bearing upon the mechanism of the pupillary changes produced by ether and chloroform. Twelve experiments were then performed to check and extend these observations and the results are the subject of the present report.

Ether and chloroform were administered by inhalation with the open cone method. The pupils were measured under constant conditions of light for any given experiment. Both eyes were examined; the pupils were found equal in all except one instance. Electrocardiographic records of the heart rate were taken at frequent intervals, making it possible in this way to correlate simultaneous effects upon the vagus and oculomotor nerves. The condensed protocols of the experiments with 2 dogs serve to illustrate the general results. The size of the pupils is expressed in percentage of the diameter of the iris. The stage of anesthesia is designated as “light” when voluntary movements as well as corneal conjunctival reflexes are present; as “deep” when these have disappeared; as “partial recovery” when the eye reflexes have reappeared; as “recovery” when voluntary movements begin.