Part II 



CARDIOVASCULAR FUNCTIONS IN DEEP HYPOTHERMIA 



HENRY E. D'AMATO 



In the preparation of this paper it was not the intention of the anthor to review 

 exhaustively all published material pertaining to the general subject. Such treat- 

 ment would require a monograph. Rather, it was intended that this paper should 

 constitute a brief demonstration, by means of published data, of the observed major 

 alterations in the dynamic functions of the mammalian heart and peripheral vessels. 

 Unless otherwise stated, the paper will ignore the occurrence and consequences of 

 all cardiac arrhythmias. Also, unless otherwise stated, all departures from normal 

 which are observed in deep hypothermia are completely reversible upon rewarming. 



Heart rate and arterial pressure. The profound bradycardia which is charac- 

 teristic of the dog in deep hypothermia is shown in figure 1. The graph was drawn 

 from the tabulated data of Hook and Stormont.^ The figure illustrates the marked, 

 progressive slowing of the heart rate from 160 beats per minute at a rectal tempera- 

 ture of 38° C, to about 20 beats per minute at 18° C. 



Hegnauer, Schriber and Haterius- recorded the pulse rate of dogs at shorter inter- 

 vals throughout the cooling process and obtained the average curve shown in figure 2. 

 At corresponding temperatures the heart rates of figures 1 and 2 are almost identical. 



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DEEP RECTAL TEMPERATURE 



Pig. 1. — Heart rate in hypotlicrmia. (From Hook and Storniont, Am. J. Physiol. B3: 334, 1941.) 



146 



