FLOW OF BLOOD IN MESENTERIC VESSELS 



I44I 



species are exceedingly sensitive to abdominal trauma. 

 In the human, portal flow is usually estimated on the 

 assumption (from studies with the dog) that two- 

 thirds to three-fourths of the total hepatic flow as 

 determined by the Bromsulfalein technique (800- 

 850 ml/min m 2 ) is derived from the portal vein. On 

 this basis, the portal venous flow is 530 to 640 ml per 

 min per m 2 , somewhat less than 20 per cent of the 

 cardiac output. 



PARTITION OF TOTAL BLOOD FLOW 



Major Organs 



Two investigators, Burton-Opitz and Sapirstein, 

 have measured the blood flow through all the major 

 mesenteric organs. The former measured gastric 

 flow (29) by placing a stromuhr in the gastrosplenic 

 vein, ligating the pancreatic and splenic branches. 

 Ligation of the gastroduodenal and pyloric veins 

 presumably forced all the gastric venous drainage 

 through anastomotic channels into the stromuhr. 

 He obtained a mean flow of 0.25 ml per min per g 

 of stomach in dogs with a mean arterial pressure of 

 85 mm Hg. In another group of animals (27) he 

 placed the stromuhr in the common mesenteric vein 

 thus obtaining the blood flow through all the intestine 

 except the duodenum which is drained by the pan- 

 creaticoduodenal vein. At a mean arterial pressure 

 of slightly less than 100 mm Hg, the mean flow was 

 0.31 ml per min per g of intestine. His measurements 

 of pancreatic blood flow (31) were more difficult to 

 make as this organ is supplied and drained by num- 

 erous vessels. He placed the stromuhr in the gastro- 

 duodenal artery, ligated the right gastroepiploic 

 artery, and so obtained the flow through the superior 

 pancreaticoduodenal artery. This vessel supplies the 

 body of the pancreas and a portion of the duodenum. 

 The head of the pancreas receives arterial blood by 

 way of the inferior pancreaticoduodenal, a branch of 

 the cranial (superior) mesenteric, and the tail of the 

 organ by way of branches of the splenic artery. In 

 two animals he was able to separate the body of the 

 pancreas from the duodenum and so obtained the 

 pancreatic flow alone. The mean flow was 0.8 ml 

 per min per g at 1 10 mm Hg. To measure the splenic 

 blood flow, Burton-Opitz placed the stromuhr in the 

 splenic vein (28). In 10 animals, he obtained a 

 mean flow of 0.58 ml per min per g at an arterial 

 pressure of 98 mm Hg. 



From Burton-Opitz' data, the weights of the 



stomach, intestine, pancreas, and spleen in a 15-kg 

 dog can be estimated as 250, 500, 50, and 70 g, 

 respectively. The total blood flows through the same 

 organs would be 60, 155, 40, and 40 ml per min, 

 respectively, and the partition of the total mesenteric 

 flow about 20, 55, 13, and 13 per cent. In Sapirstein's 

 study (114) the partition of blood flow was determined 

 directly. He obtained values of 13, 72, 8, and 7 per 

 cent for the same organs. 



The discrepancies in these two sets of data may 

 be due to one or more of several factors. As stated 

 earlier, Sapirstein's dogs were much smaller than 

 those of Burton-Opitz. In the former the weight of 

 the intestines was greater in relation to the weights 

 of the other mesenteric organs than in the latter. 

 Further, Sapirstein's dogs were anesthetized with 

 sodium pentobarbital and presumably had arterial 

 pressures 30 to 40 mm Hg higher. Finally, the meas- 

 urement techniques used may have resulted in er- 

 roneous values for one or more organs in the study. 

 It is possible that the resistance offered by the stro- 

 muhr to the intestinal venous outflow may have 

 caused Burton-Opitz to underestimate the propor- 

 tion of the total flow that passed through the gut. 

 On the other hand, Sapirstein's method may result 

 in either an underestimate or an overestimate of 

 flow through an organ. His assumption that con- 

 stancy of isotope content with time in all organs im- 

 plies identical extraction ratios is not wholly justified. 

 It is probably not too much in error as the extraction 

 ratio for radiopotassium in the first few seconds after 

 injection is nearly one for all organs. However, isotope 

 constancy can be observed in the presence of different 

 extraction ratios if the potassium ion concentrations 

 of the organs differ, as they do. 



In order to compare the data of Burton-Opitz 

 and Sapirstein for any one organ with data obtained 

 by other investigators, it is desirable to express the 

 flows per unit weight of organ. Also, an attempt must 

 be made to normalize the values to some kind of 

 average animal. For Burton-Opitz' results this can 

 be done by correcting to an arterial pressure of 

 1 30 to 1 40 mm Hg, assuming that the flow increases 

 linearly with arterial-venous pressure difference. 

 The following values are thus obtained : stomach, 

 0.4; intestine, 0.4; pancreas, 1.0; and spleen, 0.8 

 ml per min per g of tissue. Sapirstein's values for the 

 same organs are 0.4, 0.7, 1.0, and 0.6, respectively. 

 These values were obtained by taking the cardiac 

 output to be 170 ml per min per kg. If Sapirstein's 

 distribution is applied to 1 5- or 20-kg animals with 

 a cardiac output of 125 ml per min per kg, his values 



