Studies on small intestinal obstruction.

Abstract

The results of the present study can be summarised by the following answers to the framed questions: (I) Simple small-bowel obstruction in the cat entails predominantly a distension of the intestine, whereas the sustained intraluminal pressure is rather modest, between 5 and 10 mmHg. Spontaneous bowel activity is still present after 72 hours and responds to pharmacologic stimulation (II) Haemodynamic and microcirculatory evaluation in vitro shortly after release of an in vivo obstruction reveals no difference between obstructed and non-obstructed intestine; after decompression, thus any impairment of bowel "viability" caused by obstruction is rapidly ameliorated. (III) A moderate distension of short duration increases regional vascular resistance in non-obstructed intestine but compromises neither capillary filtration rate nor oxygen consumption. Upon a further and considerable distension, both haemodynamic and microcirculatory variables deteriorate in parallel; at an intraluminal pressure of 100mmHg, 30% of the blood flow and probably less than 15% of the perfused capillary surface area are preserved. Thus, the intestinal microcirculation is not interrupted until an 'unphysiologic' distention is applied. (IV) After release of an in vivo obstruction, a considerable distension produces the same circulatory responses as those recorded in non-obstructed intestine, whereas a moderate distension compromises the capillary function in obstructed but not in non-obstructed intestine; it is suggested that this is mainly the result of enhanced bowel-wall distensibility in obstruction. (V) A moderate and sustained distension occasions a 50-60% resistance augmentation in non-obstructed bowel and a 45-50% reduction of the perfused capillary surface area but does not compromise the oxygen uptake; thus, moderate distension involves no threat to bowel microcirculation or 'viability'. The experimental procedure per se entails some degree of resistance augmentation and CFC reduction during a 3-hour perfusion; however, no changes appear during the initial stage, i.e., corresponding to the period of artificial distension...