In nine dogs under pentobarbital anesthesia, electromagnetic flow transducers were implanted around the ascending aorta, brachiocephalic artery, superior mesenteric artery, and iliac artery. A catheter to measure arterial pressure was implanted into the thoracic aorta. After full recovery, hemodynamic variables were measured daily in conscious dogs in five sets of recordings: control, during anticipation of food, during actual food intake, and 1 hour and 3 hours after completion of ingestion. During food intake there was a generalized sympathomimetic stimulation characterized by a significant increase in cardiac output with a peak of 142%, heart rate (176%), arterial blood pressure (147%), while the ratio of flow in the superior mesenteric artery to cardiac output decreased from 8.9% to 7.6% (P<0.05). Flow in the brachiocephalic artery increased during food intake to 196% and that in the iliac artery dropped to 75.4%. The possibility was discussed that a certain level of sympathomimetic stimulation may signal the diminishing or ending of ingestion. During digestion (at 1 and 3 hours after ingestion), there were no significant changes in cardiac output, heart rate, and mean arterial blood pressure, whereas the flow in the superior mesenteric artery increased to 133% and mesenteric regional resistance decreased to 82%, and flows in the brachiocephalic and iliac arteries decreased to 86.5% and 74.6%, respectively. The ratio of flow in the superior mesenteric artery to cardiac output increased to 8.9% and 12.5% in the third hour. These results indicate that a redistribution of blood flow occurs during digestion with a preference for the vascular bed of the superior mesenteric artery.
This study demonstrated a significant reduction in common femoral venous flow during laparoscopic cholecystectomy coincident with pneumoperitoneum and reverse Trendelenburg's position. Intermittent sequential pneumatic compression reversed that effect, returning peak systolic velocity to normal.
In addition to its role in absorbing nutrients, the intestinal mucosa provides an important barrier against toxins and bacteria in the bowel lumen. This study evaluated changes in rat jejunal permeability and histology after total parenteral nutrition (TPN) or TPN supplemented with glutamine. Lactulose and mannitol were used to measure jejunal permeability, and fixed stained histologic specimens were used to measure mucosal dimensions. After the insertion of central venous catheters, 18 male rats were randomly divided into three groups: CHOW, saline infusion with a standard laboratory rat diet ad libitum; TPN; and GLN, 2% L-glutamine-supplemented TPN. The TPN and GLN groups received isocaloric, isovolumic, and isonitrogenous feedings. After 7 days of infusion, a laparotomy was performed, and lactulose and mannitol were instilled into the lumen of a 25-cm ligated segment of jejunum. Urine was collected for 5 hours and assayed for lactulose, mannitol, and creatinine. The jejunum was harvested, and wet weight, villus height, mucosal thickness, and villus width were measured. Intestinal permeability to lactulose and the lactulose to mannitol ratio significantly increased after TPN compared with CHOW, and these effects were prevented with the addition of glutamine to the TPN solution. Jejunal villus height and mucosal thickness significantly decreased following TPN but were not significantly different from CHOW when glutamine was added to the TPN solution. These data suggest that TPN was associated with increased jejunal permeability and that glutamine, when added to the TPN solution, prevented this effect. In addition, glutamine reduced TPN-associated atrophy of the jejunum.
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