DRUGS AND INTERNAL COOLING— DAMMANN axd MULLER 



437 



cent oxygen througli a cannula tied into the trachea. jNIccIianical ventilation was 

 begun at least 30 minutes before the animals were cooled. The respirator rate was 

 15 per minute in Exj^eriments 1, 2, 3, .\ 7 and M. hi all other experiments the 

 respirator rate was maintained at 30 per minute. 



Extracorporeal cooling was accomplished by means of a modified Dale-Schuster 

 pump. Blood was i)umped from the inferior vena cava via one femoral vein through 

 8 feet of plastic tubing immersed in cold water and was then returned to the animal 

 via the other femoral vein. Approximately 150 cc. of dextran solution was needed to 

 prime the pump. Electrocardiograms (leads I and 11 or I and III) and femoral 

 arterial pressures were frequently recorded. Recordings were made synchronously 

 on three channels of a Sanborne Poly-Viso oscillograph. Arterial pressures were 

 obtained from a femoral artery by means of a Sanborne electromanometer. All 

 temperatures were obtained by means of a mercury thermometer inserted approxi- 

 mately 20 cm. into the rectosigmoid. 



In most cases, cooling was continued until ventricular fibrillation or cardiac arrest 

 occurred. In a few experiments, rewarming was carried out by replacing the cold 

 water surrounding the plastic tubing with water of 35-40° C. 



The following are typical protocols : 



Series I. — Blocked Dogs, Rapid, Extracorporeal Coolixg 



Ventricular 

 Expt. tachycardia 



no. r C.) 



1 31.7 



2 33.5 



3 — 



9 27.1 



12 26.3 



13 24.0 



14 29.4 



20 26.5 



22 29.5 



Lowest 



recorded 



temp. 



(°C.) 



29.5, VF 

 27.0, VF 

 24.5, VF 

 22.5, VF 

 16.0, CA 

 23.7, VF 

 22.4, VF 

 . 25.5, VF 

 24.0, VF 



Rate of 



cooliiiR 



decrement 



per IS niin. 



(°C.) 



5.6 

 3.0 

 3.0 

 5.0 

 2.3 

 3.8 

 4.1 

 2.8 

 2.6 



Series II. — Non-Blocked Dogs, Rapid, Extracorporeal Cooling 



Ventricular 

 Expt. tachycardia 



no. r C.) 



5 20.7 



7 25.9 



8 



10 



16 . 



17 



Continued — next page 



