Assessment of gastric mucosal perfusion during simulated hypovolemia in healthy volunteers

We described here an original device for laser Doppler (LD) flowmetry measurements of gastric mucosal perfusion, which was used here in healthy volunteers. A modified nasogastric tube containing the LD probe was inserted. Aspiration via a catheter, fixed in parallel to the probe, held the probe against the gastric wall. This new device was used to assess gastric mucosal perfusion in seven volunteers during simulated hypovolemia induced by lower body negative pressure (LBNP) application. The LBNP consisted of three successive levels of depression (-10, -20, and -30 mm Hg). Although mean arterial pressure remained unchanged during negative pressure application, there was a significant decrease in cardiac output (transthoracic electrical impedance) at each stage of LBNP. In contrast, gastric mucosal perfusion decreased significantly only at higher level of sympathetic stimulation corresponding to unloading of both cardiopulmonary and arterial baroreflexes (-30 mm Hg). It may be hypothetized that local vascular mechanisms exist to maintain gastric mucosal perfusion during moderate sympathetic stimulation induced by selective unloading of cardiopulmonary receptors. In the healthy volunteers studied, we found that LD flowmetry is a valuable tool to evaluate gastric mucosal perfusion when the probe is maintained in a constant position by the technique described here.