The gastric tonometer. A valuable monitor of splanchnic perfusion?

Minimally invasive assessment of the adequacy of perfusion of the gastrointestinal tract has become clinically feasible with the availability of the gastric tonometer. This modified nasogastric tube permits calculation of the pH of the gut mucosal cells; a low tissue pH may indicate tissue hypoxia due to regional hypoperfusion. Such regional hypoperfusion is often undetected by other monitors and, if it occurs intra-operatively, may result in a poor outcome following major surgery. In critical illness, the splanchnic area seems to be particularly vulnerable to hypoperfusion and such a regional oxygen deficit is implicated in the causation of organ dysfunction/failure. Recent studies have begun to define the circumstances in which splanchnic tissue acidosis develops and several therapies have been proposed to reverse the regional oxygen deficit. This review seeks to clarify whether or not the tonometer is a valuable addition to our current monitoring aids.