334 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



Swan et al.,^ and Osborn^° on the other hand found that the serum potassium level 

 decreased in their hypothennic dogs. 



The work of Osborn^° on pH and bicarbonate levels in relation to fibrillation and 

 on ECG are of fundamental importance, and, together with the observation of 

 Swan et al.,^ that hyperventilation reduces or abolishes spontaneous fibrillation, 

 helped in directing closer attention to electrolyte balances. 



Electrolyte levels and differences in the coronary circuit have been measured. -° 

 Three groups of hypothermic dogs were considered for mutual comparisons and 

 for comparisons with their own status prior to hypothermia. These groupings, 

 which have already been considered in relation to ventricular thresholds and the 

 nature of terminal heart action are: (1 ) hypothermic, normocapneic dogs (none of 

 which fibrillate spontaneously), (2) hypothermic, acidotic dogs which fibrillate 

 terminally, and (3) acidotic hypothermic nonfibrillators. Dogs artificially respired 

 during cooling for pH control were automatically in group 1. whereas the grouping 

 of the acidotic (spontaneously respiring) hypothermic dogs w^as made on the basis 

 of terminal cardiac action. 



Coronary venous samples were taken from the great circumflex vein both at 

 normal temperature and after cooling to 24°. After each sample the chest was 

 closed and the pneumothorax reduced, permitting spontaneous respiration in groups 

 2 and 3, and cooling was continued to terminus. 



The electrolytes measured in all samples were sodium, chloride, potassium, cal- 

 cium, magnesium and hydrogen ions (pH). Summaries of the coronary A-V dif- 

 ferences are given in tables I and II. Table I contains the means (and standard 



TABLE I 



Coronary A-V Electrolyte Differences in mEq. per Liter in Twenty-six Dogs Prior to 

 Subjection to Immersion Hypothermia 



Total 



, ' , 



pH Ca K Na CI Mg 



Group 1 +0.01 —0.2 +0.10 —2.0 —3.0 —0.20 



8 normocapneic non-fibrillators (±0.02) (±0.24) (±0.10) (±2.0) (±L6) (±0.08) 



Group 2 +0.02 —0.1 0.0 —5.0 —0.5 —0.20 



10 hypercapneic fibrillators (±0.01) (±0.18) (±0.13) {±2.2) (±1.2) (±0.12) 



Group 3 +0.03 —0.2 +0.12 —6.0 0.0 —0.20 



8 hypercapneic mm-fibrillators (±0.01) (±0.22) (±0.18) (±2.4) (±2.0) (±0.04) 



TABLE II 



Coronary A-V Electrolyte Differences in mEq. per Liter, Measured in Three Groups of 



Hypothermic Dogs at 24° C. 



Total 



pH Ca K Na CI Mg 



Group 1 +0.03 —0.2 —0.1 —3.0 +2.0 —0.2 



8 normocapneic non-fil)rillat()rs (±0.01) (±0.15) (±0.16) (±1.^) (±1.5) (±0.04) 



Group 2 +0.08 +0.4 —0.2 —3.0 0.0 0.0 



10 hypercapneic ril)rillal()rs (±0.04) (±0.34) (±0.59) (±2.6) (±0.97) (±0.11) 



Group 3 +0.03 —0.1 0.0 —3.0 +1.5 —0.3 



8 hypercapneic non-ril)rillat()rs (±0.01) (±0.16) (±0.18) {±2>2) (±1.8) (±0.07) 



