The effects of three vaporizable fire extinguishing agents on myocardial metabolism and cardiovascular dynamics in the anesthetized dog

Thirty-four mongrel dogs were divided into five groups: (1) six O 2 controls; (2) eight exposed to 27–75% CBrF 3 in O 2; (3) four exposed to 27–75% N 2 in O 2; (4) nine exposed to 4–12% bromochlorodifluoromethane in O 2; and (5) seven exposed to 0.3–1.0% chlorobromomethane in O 2. Dogs were anesthetized and instruments for cardiovascular dynamic and myocardial metabolic monitoring through thoracotomies were implanted. Thirty-eight variables reflecting cardiovascular dynamics and myocardial metabolism were monitored before, during, and after 45-min exposures to the respective compounds. The results of the exposures to the halogenated alkanes were compared with the results from the O 2 experiments except where significant differences were detected between O 2 and N 2 exposures reflecting effects of oxygen exclusion, in which cases the results of the corresponding fluorocarbon exposures were compared with the results from the N 2 exposures. The most significant observation was the elevation of the coronary sinus blood PO 2 and O 2 content during exposure to CBrClF 2 or CH 2BrCl. Both of these variables increased in magnitude progressively during the exposures. The persistence of the effect postexposure was greater for CBrClF 2 than for CH 2BrCl. Exposure to CBrF 3, CBrClF 2, or CH 2BrCl may result in disturbances of myocardial energy metabolism that are connected to myocardial performance. Based on the concentration to which dogs must be exposed to elicit such responses, CBrF 3 was least effective and CH 2BrCl was most effective. The CBrClF 2 was intermediate between the two but closer to the CH 2BrCl than to the CBrF 3.