OBSERVATIONS ON CYCLOPENTANE AS AN ANESTHETIC AGENT

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Abstract
The anesthetic properties of cyclopentane, obtained in a pure state from petroleum, were studied. Young adult Swiss mice were anesthetized in a test jar by evaporating measured quantities of volatile agents. Provision was made for the absorption of exhaled CO2. The anesthetic index (ratio of concn. of agent for respiratory arrest to concn. for surgical anesthesia) for ether on 33 mice was 2.07 as compared to 1.56 for cyclopentane on 65 mice. Most mice went to sleep with about 8% cyclopentane, and respiratory arrest occurred with about 12%. Induction of anesthesia with cyclopentane was rapid, especially when the concn. was 8% and above. Recovery was also rapid, varying from 35 to 145 seconds, when concns. of 7-13% were used. Respiratory arrest occurred before cardiac arrest; however, great difficulty was encountered in resuscitating mice with respiratory arrest. During the induction of dogs, more excitement occurred with cyclopentane than with ether. Cyclopentane, like cyclopropane, sensitized the conduction system of the heart to epinephrine, although the irregularities of cardiac rhythm were less striking than with cyclopropane. Electrocardiographs studies on dogs, given dibenamine, followed in several hours by the injn. of epinephrine under cyclopentane and cyclopropane anesthesia, revealed no irregularities of rhythm, except for slight sinus tachycardia. Because of its relatively low anesthetic index, the pronounced excitement even during rapid induction, and the occasional death at low concns., cyclopentane is not recommended as an anesthetic agent.