April 21, 1922] 



SCIENCE 



435 



SUMMARY OF RESULTS SHOWING PERrTJSION TIME TOR 1 C.C. OF PHYSIOLOGIC SODIUM CHLORID SOLUTION 

 IN RELATION TO BLOOD PRESSURE IN MUSCLE INJURY SHOCK 



kept at a constant pressure by connecting the 

 injection burette with a large bottle containing 

 air at a constant pressure as indicated by a 

 mercury manometer. A side tube on the 

 burette connected with a bottle of noi-mal saline 

 solution served to reiill the burette to the 

 original level after each perfusion. In making 

 a determination of the perfusion rate, about 

 3 C.C. of fluid was allowed to run into the artery 

 while the time was being recorded mth a stop 

 watch. Such a determination required but a 

 few seconds, and immediately after the clip on 

 the main trunk was removed, thus allowing the 

 part to receive its natural blood supply. 



Cats, anesthetized with ethyl carbamate 

 (urethane), were used. Shock was produced 

 by the method described by Cannon.* The 

 muscles of the right leg only were crushed, 

 those of the left being left intact for the inflow 

 measurements. In a few instances in which 

 perfusion was interfered with by small clots 

 forming in the vessels, the experiments were 

 discarded. The condition of the vessels was 

 tested by inflow determinations after death, 

 when, if there is no obstruction, the rate of 

 inflow is greatly increased. A blood pressure 

 record was obtained from the right carotid by 

 means of a mercury manometer. 



A summary of the results is given in the 

 table. The figures represent the time in sec- 

 onds for the entrance of 1 c.c. of fluid, and in 

 each case they are the average for at least 

 three determinations. Frequently at the be- 



4 Cannon: Arch, of Surg., 1922, IV: 7. 



ginning of an experiment .the readings indi- 

 cated considerable variation in vascular tone, 

 necessitating a number of observations to deter- 

 mine the control rate. Invariably there was a 

 gradual increase in the time ((. e., decrease in 

 the rate) of inflow after muscle injury, usually 

 starting within the first hour and reaching a 

 maximum in from two to four hours. After 

 this a dilation occuiTed which continued until 

 the death of the animal and was accompanied 

 by a further fall in blood pressure. As already 

 stated, the perfusion rate was still further 

 increased after death. A curve showing the 

 general relation between the blood pressure and 

 the tone of the blood vessels during the devel- 



HnSei 



MO - leg crushed 



Wood Pressure 



too 



T^rfudion Time 



J L 



rtoors 



Curve plotted from the averages of six experi- 

 ments showing the relationship between the per- 

 fusion rate and the blood pressure in muscle 

 injury shock. As the blood pressure falls, there 

 is a slowing of the perfusion rate, indicating 

 an increased tone of the arterioles. 



