Effect of Carbon Dioxide on Ether Anesthesia.

Abstract

In anesthesia, more especially where there is any significant amount of rebreathing, it is evident that the patient is inhaling a gas mixture containing considerable amounts of CO_2. As was established long ago and as has again been shown by Leake and Waters, 1 30 to 40% of CO₂ has distinct anesthetic properties. It, therefore, seems possible that in anesthesia where the patient is breathing fairly high percentages of CO₂, this gas may be acting synergistically or additively with the anesthetic given, and exerting an appreciable anesthetic action. It also seems reasonable that if such be the case, CO₂ might be administered simultaneously with other anesthetics with the object not only of stimulating the respiration but also to act as an adjuvant to them.

To test these views we have studied the effect of CO₂ on ether anesthesia in some 50 experiments on 11 full grown white rats with the following results:

Moderately deep anesthesia∗ almost invariably resulted from the inhalation for 30 minutes of air containing 3.5 to 3.8% ether and CO₂ of from 1 to 2% (arising from the rat's metabolism). Less than 3.5% of ether with similar low percentages of CO₂ caused incomplete anesthesia, except that, in one experiment, fairly complete anesthesia was obtained with 3.32% ether with 1% CO_2. Attempts to obtain a like result with similar percentages in the same rat and in several others failed in any of 5 such experiments.