Experimental studies on Damage Control Surgery and Intraabdominal Hypertension
Abstract: Damage control surgery (DCS) offers an alternative to the traditional surgical management of complex or multiple injuries in critically injured patients. If a patient survives the initial phase of DCS, complications may occur, one of these being intraabdominal hypertension (IAH) and it´s potential development into the abdominal compartment syndrome.The indications for DCS have been widened and DCS principles can be applied in situations where time and resources are essential factors. The DCS principles of rapidly controlling intestinal spillage have not been evaluated. The aim of the studies in Papers I and II was to evaluate the principles of spillage control of intestinal contents according to the DCS concept and more specifically the effects of early rapid control of multiple bowel perforations on cardiovascular and pulmonary function compared with conventional small bowel resections in an animal model with abdominal trauma. In Paper I the animal model using anaesthetised pigs included a gunshot wound to the abdomen which caused multiple small bowel injuries. Haemorrhagic shock was combined with the gunshot wound in Paper II. The results presented in Paper I showed a significant reduction in rise in systemic vascular resistance and pulmonary vascular resistance, and a trend towards higher cardiac output and lower oxygen consumption in the bowel ligation group. In Paper II the results show a longer persistence of lactic acidaemia in the bowel ligation group. The aim of the study in Paper III was to assess visceral (intestinal, gastric and renal) microcirculation parallel with central haemodynamics and respiratory function during stepwise increases in intraabdominal pressure. In Paper IV we studied mucosal barrier function and morphology in the small bowel and colon of the pigs which were subjected to IAH. The IAP in anaesthetised pigs was increased stepwise using CO2 inflation, by 10 mm Hg at 10-minute intervals up to 50 mm Hg, and followed by exsufflation (Paper III). The microcirculation was selectively studied using a 4-channel laser Doppler flowmeter (Periflex 5000, Perimed, Sweden). The mucosal tissues were mounted in modified Ussing chambers for assessment of barrier function (E.coli K12 uptake and 51Cr-EDTA permeability) (Paper IV). The results showed that the microcirculation of the small bowel mucosa and colon mucosa was significantly less affected compared to the seromuscular layers. The microcirculation of gastric mucosa, renal cortex and the seromuscular layer of small bowel and colon were significantly reduced with each increase. Cardiac output (CO) decreased significantly at IAP levels above 10 mm Hg and the respiratory function data showed an increasing airway pressure and a concomitant reduction in thoracic compliance. Transmucosal passage of E. coli was increased three-fold in the small bowel after ACS with a significant correlation to the degree of mucosal microcirculatory reperfusion after exsufflation. 51Cr-EDTA permeability was unaffected. Bacterial passage in the colon was unchanged, whereas 51Cr-EDTA permeability after ACS increased by up to 181% of baseline and was correlated to significant histopathological changes in the mucosa.In Paper I we have demonstrated that early rapid control of multiple bowel perforations in a model with moderate shock resulted in less impairment of SVR and PVR than conventional resection and anastomosis. The use of DCS principles, however, had no beneficial effect on cardiovascular function when haemorrhagic shock was combined with abdominal missile trauma (Paper II), on the contrary bowel ligation was followed by more prolonged lactic acidosis than conventional repair. The studies in Paper III and IV indicate that the microcirculation of intestinal mucosa and especially small bowel mucosa seem better preserved in response to intraabdominal hypertension caused by CO2 insufflation than other intraabdominal microvascular beds. The short term ACS in this model caused morphological changes in the intestinal mucosa, and mucosal barrier dysfunction. The response pattern concerning barrier function changes after CO2 insufflation differs between small bowel and colonic mucosa. The small bowel mucosa showed increased bacterial passage, and the colonic mucosa an increase in paracellular permeability and secretory response.
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