Gastric tonometry

Background The gut is one of the most susceptible organs to hypoperfusion during conditions of trauma or stress. More than three decades ago, Price and colleagues removed 15 percent of the blood volume from healthy volunteers, causing a 40 percent reduction in splanchnic blood volume. In this study, cardiac output (CO), blood pressure (BP), and heart rate (HR) did not change from baseline. A more recent study was conducted by Hamilton-Davies and associates, in which 25 percent of the blood volume was removed from six healthy volunteers. Gastric mucosal perfusion, as measured by saline gastric tonometry, was the first variable to decline (in five of the six subjects). Stroke volume (SV) also decreased; however, routinely measured cardiovascular variables such as HR, BP, and CO did not change significantly enough from baseline values to cause suspicion of a hypovolemic state. These studies suggest that during periods of hypovolemia, the gut vasoconstricts, thus shunting blood toward “more vital organs,” such as the heart and brain. Gut hypoperfusion can progress to ischemia, which may result in complications that take place many hours and days following an episode of hypovolemia.