1442 



HANDBOOK OF PHYSIOLOGY ^ CIRCULATION II 



would all be reduced by some 25 per cent; that is, 

 with the exception of the intestine, they would be 

 lower than those of Burton-Opitz. 



Of the other workers who have measured gastric 

 blood flow, Boenheim (18) collected the venous 

 drainage directly and obtained a mean flow of 0.26 

 ml per min per g at the very low arterial pressure 

 of 60 mm Hg. Lim et al. (94) perfused with a donor 

 dog an isolated surviving stomach and collected the 

 venous outflow to find a mean value of 0.34 ml per 

 min per g at a perfusion pressure of 100 mm Hg. 

 Recently, Salmon et al. (112) used a method similar 

 to that of Boenheim's in dogs with blood pressures of 

 130 to 150 mm Hg and obtained a mean flow of 

 0.37 ml per min per g. 



The literature contains widely varying values for 

 the blood flow through the intestines. Selkurt et al. 

 (119) measured mesenteric venous outflow in dogs 

 anesthetized with sodium pentobarbital and having 

 pressures of 1 30 mm Hg or more. They found a mean 

 flow of 8.7 ml per min per kg body wt which is 

 equivalent to about 0.2 ml per min per g organ. 

 In a later study with a rotameter, Selkurt (120) 

 obtained flows 50 per cent or higher, but no body- 

 weights were given so direct comparison cannot be 

 made. 



A large number of measurements of venous outflow 

 from segments of small intestine have been made in 

 the writer's laboratory in the past few years. These 

 were innervated and denervated segments, in situ, 

 in dogs weighing 1 2 to 20 kg, anesthetized with 

 sodium pentobarbital and having arterial pressures 

 of 1 20 to 1 50 mm Hg. Although there was a large 

 variation in values from segment to segment, the 

 mean flows were about 0.6 ml per min per g, being 

 slightly higher in the upper jejunum than in the 

 lower ileum. These values were obtained with a 

 venous pressure of zero. When the venous pressure 

 was elevated to 10 mm Hg, the flow was generally 

 reduced by 10 to 15 per cent. 



Brodie and co-workers (23, 24) measured the 

 blood flow through small intestinal segments 

 plethysmographically and obtained a mean value of 

 0.4 ml per min per g. Neely & Turner (103) used a 

 somewhat similar technique, measuring weight 

 changes following venous occlusion to find 0.28 ml 

 per min per g. Results of such studies as these two 

 must be considered in light of the prompt rise in 

 intestinal vascular resistance which follows an acute 

 rise in venous pressure [see, for example, Selkurt & 

 Johnson (122) and Johnson (85)]. 



Selkurt et al. (121) artificially perfused segments of 



ileum and obtained flows with an arterial-venous 

 pressure difference of 130 mm Hg of about 0.25 ml 

 per min per g. This is much lower than flows ob- 

 tained with similar preparations in this writer's 

 laboratory. In our early work, very low flows were 

 frequently obtained; however, more normal flows of 

 0.5 to 0.6 ml per min per g were usual in later ex- 

 periments. The cause of the vasoconstriction in 

 intestinal segments which follows arterial cannulation 

 is not known to this writer, but it seems to be generally 

 prevented by topical application of procaine at the 

 site of the cannulation. This vasoconstriction can at 

 times be so intense as to reduce blood flow to less 

 than 0.05 ml per min per g. 



Geber (54) has recently placed an electromagnetic 

 flowmeter on cannulae placed in the arterial circuit 

 of segments of dog's intestine and obtained very 

 high flows. His values were duodenum, 1 .38; jejunum, 

 0.98; ileum, 0.82; and colon, 0.73 ml per min per g. 

 It is difficult to believe that these values are not falsely 

 high. If correct, the intestinal venous outflow would 

 be equal to or greater than the total portal venous 

 flow as measured by most workers. It is possible that 

 Geber trimmed the mesentery from the intestinal 

 segments before weighing them. In some animals, 

 this would reduce the segment weight by 25 to 50 

 per cent, and thus result in high estimates of the 

 perfusion rates. 



Several investigators have attempted to measure 

 the blood flow through the cranial mesenteric artery 

 of the dog. Trapold (132) using a Shipley rotameter 

 and Deal & Green (38) using an electromagnetic 

 flowmeter found flows in the range of 10 to 60 ml per 

 min, the average being less than 2 ml per min per kg 

 body wt. This is a surprisingly low value; with the 

 exception of the flow through the relatively small 

 caudal mesenteric artery, the cranial artery supplies 

 the same tissues as are drained by the common mesen- 

 teric vein. It is possible that manipulation of the 

 mesenteric artery may result in vasoconstriction just 

 as does cannulation of the intestinal arteries. Cull 

 et al. (36) obtained higher flows in the cranial mesen- 

 teric artery (120 ml/min in dogs of unspecified 

 weights), but these are still significantly lower than 

 would be expected. Grodins et al. (71) used a thermo- 

 stromuhr to obtain mesenteric artery flows of a 

 more expected value of 1 2 ml per min per kg. Meyer 

 (100) ligated the gastroduodenal and caudal mesen- 

 teric arteries and collected venous outflow from that 

 part of the gut supplied by the cranial artery (je- 

 junum, ileum, and proximal portion of the colon). 

 He obtained flows of the same order as those of 



