ABSTRACT
OBJECTIVE: Nitric oxide (NO) mechanisms have been shown to modulate fasting small intestinal motility in humans, but a role in the regulation of human postprandial small intestinal motility has not been assessed. The aim of this study was to evaluate the effect of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) on the regulation of small intestinal nutrient transit and postprandial small intestinal motility in healthy humans. MATERIAL AND METHODS: Seven healthy male volunteers (18-27 years) underwent antroduodenal manometry recordings for 4 h on 2 occasions after intraduodenal instillation of a 500 KJ [120 Kcal] test meal. The meal was administered 15 min after the commencement of a 60-min intravenous infusion of L-NMMA (4 mg kg-1 h-1) or saline (0.9%). Studies were separated, performed in randomized order and >3 days apart. The frequency and amplitude of duodenal pressure waves together with time to return of fasting motility (phase III) was determined. On each day, small intestinal transit was measured using a lactulose breath test. RESULTS: The test meal interrupted fasting small intestinal motility in all subjects. The time to recurrence of fasting motility following its postprandial disruption was similar (L-NMMA versus saline 1.6+/-0.2 h versus 1.9+/-0.1 h; p>0.05). Duodenocaecal transit was delayed by infusion of L-NMMA compared with saline (L-NMMA versus saline 92.1+/-3.9 min versus 66.4+/-6.4 min; p<0.005). Infusion of L-NMMA significantly increased the frequency (L-NMMA versus saline 50.4+/-6.6 versus 34.8+/-5.5 waves per 30 min; p<0.05) and amplitude (L-NMMA versus saline 20.4+/-1.5 versus 15.5+/-1.1 mmHg; p<0.01) of duodenal pressure waves. CONCLUSIONS: These data suggest that endogenous NO may play a role in the regulation of small intestinal nutrient transit by regulating small intestinal motility in healthy individuals.
Subject(s)
Gastrointestinal Transit/drug effects , Gastrointestinal Transit/physiology , Intestine, Small/physiology , Nitric Oxide/metabolism , omega-N-Methylarginine/administration & dosage , Adolescent , Biological Transport/drug effects , Biological Transport/physiology , Breath Tests , Humans , Infusions, Intravenous , Intestine, Small/drug effects , Male , Manometry/methods , Myoelectric Complex, Migrating/physiology , Nitric Oxide/analysis , Postprandial Period , Reference Values , Risk Assessment , Sensitivity and Specificity , Single-Blind MethodABSTRACT
To study the simultaneous variations of end-tidal CO2 pressure (PetCO2) and aortic blood flow (ABF) during modifications of tissue perfusion, continuous noninvasive hemodynamic monitoring and continuous recording of PetCO2 were performed on 30 patients under general anesthesia and artificial mechanical ventilation. The 30 patients underwent orthopedic surgery on one of the lower limbs using a hemostatic tourniquet. Deflation of the pneumatic tourniquet resulted in a rise of ABF up to 39% (P<0.001), a rise of PetCO2 up to 17% (P<0.001), and a drop of total vascular systemic resistance (TVSR) of 59% (P<0.001). In all cases, the gradient of Paco2-PetCO2 showed mean variations of 1.2±0.5 mmHg. According to these results, the observed variations can not be explained by an alteration of the Ventilation/Perfusion (Vo/Q) ratio alone. It may be suggested that tissue hypoperfusion produced by a tourniquet generates CO2 and other metabolic products accumulation in tissues, which are removed during reperfusion. This would be expected to produce parallel increases in ABF and PetCO2. If the results are confirmed with further studies, rapid variations of PetCO2 during anesthesia may provide a noninvasive means of assessing the quality of global tissue perfusion.
