ObjectivesTo determine changes in the absorption of lactulose and mannitol in patients undergoing laparotomy following blunt or penetrating trauma and to correlate any changes in permeability with the severity of injury.DesignNonrandomized study within patient control.PatientsConsecutive patients admitted to the trauma unit following blunt or penetrating trauma with intra-abdominal injuries warranting emergent celiotomy and jejunal access.InterventionsIntestinal permeability was measured in 18 patients within 48 hrs posttrauma by the bolus infusion into the jejunum of nonmetabolized probe molecules, lactulose (molecular weight of 342) and mannitol (molecular weight of 182). Because several patients did not tolerate the bolus infusion, a 3-hr continuous infusion of the probe molecules was used in the last eight patients entered into the study. Intestinal permeability was reassessed before discharge or on days 10 to 12.Measurements and Main ResultsThere was a decrease in urinary lactulose excretion and the lactulose/mannitol ratio between the initial posttrauma measurement and the follow-up permeability measurement using both the bolus infusion (lactulose: initial 0.13 +/- 0.032 vs. follow-up 0.047 +/- 0.012 mmol/6 hrs, p <or=to .05; lactulose/mannitol: initial 0.067 +/- 0.012 vs. follow-up 0.044 +/- 0.012, p = .11) and the continuous infusion (lactulose: initial 0.044 +/- 0.013 vs. follow-up 0.014 +/- 0.002 mmol/2 hrs, p <or=to .05; lactulose/mannitol: initial 0.055 +/- 0.020 vs. follow-up 0.015 +/- 0.007, p <or=to .05). Urine excretion of mannitol was not significantly different between posttrauma and follow-up measurements of intestinal permeability, regardless of the technique used to infuse the lactulose and mannitol. Although the decrease in lactulose and the lactulose/mannitol ratio was significant, only one third of the patients had dramatically increased permeability at the initial measure. Abdominal Trauma Index and Injury Severity Score did not correlate with urinary lactulose excretion or the lactulose/mannitol ratio. Patient tolerance of jejunal administration of lactulose and mannitol was better, using a 3-hr continuous infusion of a dilute solution compared with bolus infusion.ConclusionsIntestinal permeability is increased in the first 48 hrs posttrauma and decreases with recovery. Although one third of the patients had highly increased lactulose/mannitol ratios posttrauma, severity of injury, assessed by common scoring techniques, did not correlate with the degree of permeability. Tolerance to jejunal administration of lactulose and mannitol is improved with a slow infusion of a dilute solution over a 3-hr period compared with bolus administration.(Crit Care Med 1995; 23:660-664)