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The influence of segmental small intestinal ischemia on the central circulation and on the regional blood flow to consecutive segments of the small intestine in the rat was investigated with the microscphere method. Ischemia was established by ligating 11 arterial mesenteric end arcades, corresponding to one quarter of the total length of the small intestine. The blood supply to different organs and central circulatory variables were determined before, and 10 min, 30 min, 2 h and 14 days after the establishment of the ischemia. After 10 min of ischemia, there was an increase of the blood flow to the segments distal to the ischemic region but after 30 min, this blood flow was the same as the control flow. The central circulatory variables weere not affected. After 2 h of ischemia, the blood supply to both the ischemic and the non-ischemic part of the small intestine had deteriorated considerably. Thus, the vascular resistance in the ischemic segments and the segments surrounding it was increased. Cardiac output was reduced by about 50%. In the experimental group investigated 14 days after establishment of the ischemia, the mortality rate was about 50%. In the survivors, the intestinal blood supply had returned to normal.

Radioactive test substances were infused slowly into the duodenum of conscious rats via a permanent catheter starting 2, 12 and 24 h after a standardized laparotomy. Two differently labelled but otherwise identical test substances were used. The first test substance (125I-PVP) was infused for 4 h, the second (131I-PVP) for the remaining 1 h of the 5-hour infusion period. Immediately after the infusion the animals were killed, and the radioactivity emanating from each isotope was recorded from the excised bowel specimen. The bowel length passed by the border zone and the degree of overlap between the labels in this zone were taken as measures of propulsion and mixing, respectively. Propulsion and mixing were uninfluenced by laparotomy as measured 2--17, 12--17 and 24--29 h after laparotomy. The present findings indicate that laparotomy is not followed by a disturbance in the capability of the small bowel to transport and mix chyme, at least when no high demands with respect to chyme volume are required.

The influence of continuous intravenous infusion of dopamine on gastric evacuation, small bowel propulsion and mixing was studied in the rat. The study revealed no influence of dopamine infusion on gastrointestinal transport mechanisms.