Neither inhalative nor intravenous application of carbon monoxide modifies gastric mucosal oxygenation

This study was designed to compare the effects of different ways of administering carbon monoxide (intravenous and inhalative) on gastric mucosal oxygenation in a canine model of hemorrhage. Six chronically instrumented dogs were repeatedly anesthetized and randomized to each of the following protocols: In a first series the animals were ventilated either with 100 ppm carbon monoxide (CO) or without followed by hemorrhage and re-transfusion. In a second series a saturated CO solution was infused, compared to normal saline, again followed by hemorrhage and re-transfusion. In a control series, animals received either CO-saline or saline without any further intervention. Microvascular oxygenation of the gastric mucosa (mu HbO(2)) was assessed continuously by tissue reflectance spectrophotometry. Cardiac output was measured intermittently and oxygen delivery (DO2) was calculated. The application of CO, inhalative and intravenous, increased carboxyhemoglobin levels without effect on mu HbO(2). Hemorrhage reduced mu HbO(2) in all groups, paralleled by a reduction in DO2 without any differences between groups related to the application of CO. Neither intravenous nor inhalative application of CO alters mu HbO(2) during physiological conditions or during hemorrhage. Thus, independent of the application way, low dose CO does not seem to modulate regional mucosal oxygenation in cytoprotective concentrations.