38 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



but in the tissue. The resting skeletal muscle has lost some potassium and main- 

 tained its sodium and bromine concentration, whereas the working heart muscle 

 has given up even more potassium and has taken up some bromine. 



Because of the increased ventricular irritability in hypothermia and in anoxia 

 normo- and hypothermic animals were subjected to acute anoxia by stopping the 

 respirator for three minutes. After this period blood and skeletal muscle samples 

 were taken again and the other auricle was amputated. The results { fig. 2 ) indicate 

 that the change from good oxygenation (dark column) to hypoxia (light column) 

 does not alter the plasma concentration of sodium and bromine in normothermic 

 (dotted line) and hypothermic (solid line) animals, but is accompanied by a slight 

 rise in potassium. The electrolyte concentration of the skeletal muscle at both tem- 

 peratures is not afifected by anoxia, except for a slight rise in bromine content at 

 normal temperature. In the heart muscle, however, anoxia causes a marked loss of 

 potassium in a normothermic and a less pronounced loss of potassium in the hypo- 

 thermic dog. This loss of potassium from the heart muscle during anoxia is accom- 

 panied by an increase in sodium content in the normothermic animal only. 



The changes of intra- and extracellular electrolyte transfer can be shown more 

 distinctly bv establishing a potassium to sodium ratio (fig. 3). During hypothermia 

 the skeletal muscle is able to maintain this ratio fairly w^U. whereas the heart muscle 

 undergoes a reduction of the K/Na ratio. During anoxia at normal body tempera- 

 ture the K/Na ratio of the skeletal muscle is decreased, but is maintained during 

 hypothermia. The same phenomenon in greatly exaggerated form occurs in the heart 

 muscle where anoxia causes a severe shift of the K/Na ratio in favor of sodium 

 at normal body temperature and a slighter shift during hypothermia. 



CPS/UL OR GM. 



CPS INJECTED/GM BODY WT 

 4 



PLASMA 



^■NORMAL 38*C. 



^Z3 ANOXIC 23* C. 



X - STATISTICALLY SIGNIFICANT 



MUSCLE 



AURICLE 



Fig. 2. — Changes in c(Miccntratiiins of K, Na and Wx from normal oxyocnalion to ano.xia. 



