MYOCARDIAL BALANCE OF POTASSIUM 



HENRY SWAN 



We have tried to study the ])ruhlem of the myocardial l)alance of potassium in the 

 intact animal. In order to do this we have attempted to collect the coronary outflow 

 by catheters passed down through one of the jugular veins to the coronary sinus 

 and securely tied by a suture. The catheter continues into the jugular vein, so during 

 most of the experiment the circulation is intact. A side arm is provided so at any 

 time the flow of the coronary sinus blood can be measured by draining it into a basin 

 and timing it with a stop watch. 



After the experiment the animal is killed and the heart weighed. We assume 

 approximately 46 per cent of the heart weight is left ventricle. The estimate that 

 70 i)er cent of the arterial flow of the left ventricle comes out the coronary sinus 

 then allows us to compute volume in terms of flow per gram of tissue per unit 

 of time. 



Our results parallel those of Dr. Taylor and Dr. (lollan. In the perfused heart, 

 in contrast to the perfused skeletal muscle, there was very little loss of potassium 

 with cooling. 



We find under these conditions that the potassium balance of the heart is positive 

 throughout the experiment (Table I). In this experiment the animals are cooled to 

 30° C, and there is no support of respiration. In our laboratory, the respiration 

 slows and we consistently have a fall in pH under these conditions as respiratory 

 acidosis develops. 



There is no parallelism in our data, however, between the pH and the positive 

 myocardial balance in the intact animal. As seen in the second line, in the control 

 warm situation, the animal appears to be in very slight positive potassium balance 

 in so far as the myocardium is concerned. ( )n first exposure to 30° C, the positive 

 potassium balance increases, and it is still raised one hour later. On warming, the 

 animal maintains a positive balance but not as great. 



There is a similar positive balance for i)hosph()rus. I ])resent figure 1 merely to 

 show that the animal appears to have a positive balance of both potassiuiu and phos- 

 phorus at about the same rate at all of the temperatures. These data are means of 

 eight animals. In our lal)oratory, at 30° C, the mildlv acidotic dog shows positive 

 balance of i)otassium in the myocardium. 



TABLE I 



Myocardial Balances 

 (Means and standard deviation of 8 dogs) 



Contiol 



Arterial pH 7..V± .00 



K (yitEq./Min./lOO gni. ) 2.82±1.98 



P (AiEq./Min./lOO gni. ) ().70±1.68 



42 



