ETHER ANESTHESIA: CONCENTRATIONS IN THE INSPIRED AIR AND IN THE BLOOD REQUIRED FOR ANESTHESIA, LOSS OF REFLEXES AND DEATH

¹ From the Department of Pharmacology, Vanderbilt University School of Medicine Nashville, Tennessee

1. A method for the preparation of a continuously flowing ether-air mixture is described.

2. Three methods for quantitating ether in air mixtures are compared.

3. The thermal conductivity method of gas analysis has been successfully used with ether mixtures.

4. The concentration of ether in arterial blood reaches a maximum within 30 to 60 minutes after the animal has been inspiring a constant mixture.

5. The concentration of ether in the arterial blood is approximately the same as in the venous blood after thirty to forty-five minutes on a fixed concentration.

6. Increased ventilation does not increase the concentration in the blood after the first thirty minutes.

7. With a gradually increasing concentration of ether in the inspired air, the distribution ratio of the ether between inspired air and blood is 1:10 (incomplete equilibration).

8. After forcing ether at a high concentration and then rapidly reducing it the distribution ratios of 1:13.5 to 1:14.5 are observed.

9. The distribution ratio in vitro is 1:14.5 at 37°.

10. Anesthesia with rigidity is observed at blood ether concentration of 90 mgm. per 100 cc. (average, 11 dogs); anesthesia with relaxation is observed with blood-ether concentrations of 113 mgm. per 100 cc. (average, 21 dogs).

11. The knee jerk is abolished by a concentration of 143 mgm. per 100 cc. (average, 20 dogs); the lid reflex is lost at a concentration of 150 mgm. per 100 cc. (average, 21 dogs).

12. The respiratory reflex is abolished by a blood ether concentration of 187 mgm. per 100 cc. (average, 20 dogs).

13. For satisfactory anesthesia a concentration of 4 to 4.5 per cent ether in the inspired air is desirable; this confirms the values given by Henderson (11) but is considerably higher than those of Ronzoni.