Biomedical subjects

U Ohman

Publications and source records attributed to U Ohman.

At least 55 records · Page 3Linked to original sources

PubMed1975

Studies on small intestinal obstruction.

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...

Animals↗

PubMed1975

Studies on small intestinal obstruction. I. Intraluminal pressure in experimental low small bowel obstruction in the cat.

Intra-intestinal pressure was recorded with open-tip catheters in experimental low small-bowel obstruction in the cat. At zero time the pressure was 2-4 mmHg. After 72 hours sustained intraluminal pressure ranged mainly between 5 and 10 mmHg. Long periods of inactivity alternated with short bouts of spontaneous bowel activity. During activity the pressure rose to about 20 mmHg. In motility responses elicited by cholecystokinin, momentary pressure waves amounting to 40-50 mmHg were recorded. The result of simple mechanical obstruction is predominantly a bowel distension, whereas the magnitude of sustained intraluminal pressure is rather modest. Possible effects of distension on intestinal microcirculation are discussed.

Animals↗

PubMed1975

Studies on small intestinal obstruction. II. Blood flow, vascular resistance, capillary filtration, and oxygen consumption in denervated small bowel after obstruction.

Intestinal circulation was studied during in vitro perfusion of denervated small intestine of the cat shortly after release of an in vivo small-bowel obstruction. Blood flow, vascular resistance, capillary filtration, and oxygen consumption were determined. No significant differences were demonstrated between obstructed and non-obstructed intestines. The presently studied facets of small-bowel microcirculation thus exhibit a virtually normal function 30 minutes after decompression of a bowel obstruction. The pertinent literature affords evidence that a distension impairs bowel viability; it would seem that this impairment is rapidly ameliorated following decompression of the bowel.

Animals↗

PubMed1975

Studies on small intestinal obstruction. III. Circulatory effects of artificial small bowel distension.

Feline small-bowel circulation was studied during in vitro homologous perfusion of denervated intestine, following artificial and successive elevation of the intraluminal pressure. The specimens were inflated with nitrogen in 20 mmHg increments to the 100 mmHg level. Each pressure level was maintained for a 10-minute period. After deflation the specimens were studied for a further 60 minutes. Blood flow, vascular resistance, capillary filtration, and oxygen consumption were significantly affected by the distension. In the post-distension period flow rate and vascular resistance remained on levels differing significantly from the control values, whereas capillary filtration and oxygen consumption reverted immediately to levels not differing from the control values. It is concluded that, in isolated and denervated small intestine of the cat, an elevated intra-intestinal pressure affects the consecutive vascular sections in a similar manner, probably by simple mechanical compression. Flow rate is reduced less than capillary filtration, suggesting an opening of short-circuiting shunts in the bowel wall. In the post-distension phase vascular resistance remains elevated, while the exchange circulation is rapidly and completely restored, suggesting an extensive closure of the short-circuiting shunts.

Animals↗

PubMed1975

Studies on small intestinal obstruction. IV. Circulatiory effects of artificial small bowel distension after obstruction.

Feline small-bowel circulation was studied during in vitro homologous perfusion of denervated intestine shortly after release of an in vivo small-bowel obstruction. Blood flow, vascular resistance, capillary filtration, and oxygen consumption were determined. A previous study demonstrated that any microcirculatory impairment accompanying obstruction was rapidly ameliorated after decompression of the bowel. In the present study the specimens were distended in 20 mmHg increments to the 100 mmHg level. Each pressure level was maintained for a 10 minute period. After deflation the specimens were studied for a further 60 minutes. The results indicate that the microcirculation of the previously obstructed intestine reacts to a considerable distension in essentially the same way as does that of non-obstructed intestine. Certain findings suggest, however, that, by way of enhanced distensibility, an obstruction may render the capillary bed more susceptible to a moderate in crease in intra-intestinal pressure, an increase that in itself does not reduce the capillary filtration rate in non-obstucted intestine.

Animals↗

PubMed1975

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.

Animals↗

PubMed1975

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

Feline small-bowel circulation was studied during in vitro homologous perfusion of denervated intestine after in vivo obstruction. The bowel specimens showed delayed compliance and, when compared with non-obstructed specimens, enhanced distensibility. Bowel specimens investigated during continuous distension had a normal regional vascular resistance and a normal capillary filtration coefficient (CFC) but a somewhat decreased oxygen utilization; artificial distension to 20 mmHg caused a resistance enhancement and a profound (80-90%) reduction of CFC but did not prevent oxygen consumption from attaining normal levels. An artificial distension occasions an augmentation of regional vascular resistance, whereas the distension caused by intestinal obstruction does not; the significance of this observation is discussed. Bowel specimens investigated after intra-operative decompression showed normal vascular resistance, normal CFC and normal oxygen consumption; artificial distension to 20 mmHg produced a resistance enhancement and a moderate (40-50%) reduction of CFC; oxygen consumption was not affected. Thus, an intra-operative decompression involves no augmentation of regional vascular resistance and seems to increase the ability of the capillary bed to withstand, with retained function, a renewed distension. After release of the distension, flow reduction and resistance enhancement persisted, whereas CFC returned to basal values in both groups of specimens; oxygen consumption remained on stable levels. It is emphasized that the persisting augmentation of resistance observed after decompression of the bowel is related to the in vitro situation, whereas in vivo intra-opertive decompression of obstructed bowel seems to involve no consequences of this kind. Some experiments featured fluid output to the gut lumen in the post-distension period; this observation is discussed. A normal rate of oxygen utilization accompanied the profound reduction of perfused capillary surface area noted in obstructed gut upon a moderate additional distension; possible mechanisms underlying this finding are discussed. It is concluded from the present study that a simple small-bowel obstruction, although not per se involving any serious threat to the bowel viability, renders the gut wall vulnerable to any further increment of distension or ischaemia. It is suggested that this is mainly the result of enhanced distensibility in the wall of the obstructed gut.

Animals↗

PubMed1974