Studies on small intestinal obstruction. V. Blood circulation in moderately distended small bowel

Feline small-bowel circulation was studied during in vitro homologous perfusion of denervated intestine upon artificial distension to 20 mmHg for a 60-minute period. Delayed compliance was observed, and distension evoked contractile bowel activity; each bowel contraction was accompanied by a decrease in blood-flow rate, whereas bowel relaxations coincided with augmentations of flow. Artificial distension diminished blood flow, denoting a 50-60% increase of regional vascular resistance, and elicited variable capillary filtration coefficient (CFC) responses, on the average a 45-50% reduction of the perfused capillary surface area, but did not affect the oxygen consumption rate. After release of the distension, the enhancement of vascular resistence persisted and even increased, whereas CFC returned to control level. Control experiments involving homologous perfusion but no artificial distension also featured some resistence augmentation and CFC reduction. The effects of homologous perfusion on bowel haemodynamics and viability are discussed; though the experimental procedure may occasion some degree of haemodynamic impariment, present observations and previous reports suggest that bowel viability is not significantly affected. It is concluded from the present study that a sustained and moderate distension of nonobstructed feline small bowel, perfused in vitro, involves no threat to the microcirculation or the viability of the bowel.