Fat Emboli and Shock. 



35 



as characteristic of shock, do not occur when oil as such or in 

 emulsion is injected intravenously. The only similarity consists 

 in the fact that the mean arterial pressure falls. The pressure in 

 the left auricle falls, but in the pulmonary artery and right auricle 

 rises markedly. This can be interpreted to mean only that the 

 failure of the systemic pressure is due to pulmonary emboli, a 

 fact verified by microscopical examination of the lungs by Pro- 

 fessor Ewing. As the venous and pulmonary arterial pressure 

 changes are just the reverse of those found in shock, it is pref- 

 erable, for academic as well as for therapeutic reasons, to dis- 

 tinguish circulatory failure produced by fat emboli from that due 

 to surgical shock. 



Although pulmonary embolism is apparently primarily re- 

 sponsible for the failure of arterial pressure when fat is injected 

 intravenously, the fact that some of the oil passes through the 

 pulmonary vessels and produces emboli in the systemic circuit 

 (Bissell (2) ; Warthin (3) ; preparations kindly examined by Pro- 

 fessor Ewing) raises the question whether such systemic emboli 

 may not produce circulatory failure similar to that found in shock. 

 To test this possibility, oils as such and in emulsions were directly 

 introduced into the arterial circulation via the left brachial artery, 

 thus avoiding pulmonary emboli. The effects of such injections 

 were variable, depending apparently on where the fat emboli 

 lodged. In some experiments large quantities of oil could be 

 injected without any apparent effect on the arterial pressure 

 In one case 24 c.c. of oil in emulsion and 8 c.c. as neutral oil were 

 injected without any effect on the arterial pressure. In other 

 cases the injection of oil produced a slight rise of arterial pressure, 

 after which the pressure gradually recovered to normal. In a 

 third group of cases the arterial pressure after a slight initial rise 

 fell rapidly and the animal died within a few minutes. Electro- 

 cardiograms showed that in these cases the heart was not fibril- 

 lating but that the impulses were distributed in a normal manner 

 to the last. Death was evidently due to respiratory failure 

 brought about by fat emboli of the medulla. The pressure in 

 the right auricle rose markedly, due to the cardiac failure following 

 asphyxia. In none of these cases did the circulation fail as it 

 does in shock. 



