NARCOSIS INDUCED BY CARBON DIOXIDE AT LOW ENVIRONMENTAL TEMPERATURES

¹ From the Department of Pharmacology, University of Wisconsin, Madison

A reversible state of narcosis having certain characteristics of both hibernation and anesthesia may be induced and maintained for many hours in the rat and dog by sudden exposure at 5°C. to concentrations of CO₂ of 5 per cent or greater. In this state the rat has a body temperature of 16-20°C., a heart rate of 30-100 per minute, and a respiratory rate of 1-20 per minute. When the rat is respiring 11% CO₂ at 5°C. the CO₂ content of the blood may reach 110 volumes per cent and the plasma pH a level of 7.07. A similar state may be induced in the rabbit by 20% CO₂ and cold but it is not reversible because of the fatal pulmonary edema.

Rats are rendered more susceptible to this state by fasting, prolonged (three weeks) exposure to 10% O₂, or by administration of small doses of depressant drugs.

Repeated narcotization by this method at intervals of several days; acclimatization to cold or to CO₂ for several days; or previous thyroid feeding; renders the rat partially or completely resistant to the narcosis induced by 11% CO₂ at 5°C.

A state of depression somewhat similar to, but not identical with, that described above may be produced in rats by exposure to low oxygen tensions (10%) or to high oxygen tensions (4 atmospheres) at an environmental temperature of 5°C.

It is believed that these experiments furnish additional evidence to support the view that a sudden and well marked increase in the tissue tension of CO₂ produces a definite, if temporary, decrease in the total oxidative metabolism and a parallel reduction in activity of certain body tissues including some portions of the nervous system.

This article has been cited by other articles:

				P. W. WILLARD, R. C. YERKES, and S. M. HORVATH Respiratory Gas Exchange: Experiments in Rats Induced into Cardiac Arrest by Various Procedures Arch Surg, May 1, 1962; 84(5): 525 - 532. [Abstract] [PDF]