The Gastrointestinal Tract and Critical Illness

The gastrointestinal tract has long been known to be particularly sensitive to alterations in regional blood flow that result from critical illness. 1 Arvidsson D. Rasmussen I. Almqvist P. et al. Splanchnic oxygen consumption in septic and hemorrhagic shock. Surgery. 1991; 109: 190-197 PubMed Google Scholar Gastrointestinal ischemia has been implicated in the pathogenesis of multiple systems organ failure (MSOF). 2 Meakins J.L. Marshall J.C. The gut as the motor of multiple system organ failure. in: Marston A. Bulkley G.B. Fiddian-Green R.G. Splanchnic ischemia and multiple organ failure. Edward Arnold Publishers LTD, London England1989: 339-348 Google Scholar The ischemia has been postulated to result in a permeability defect allowing translocation of bacteria and bacterial products into the portal circulation. 3 Dahn M.S. Lange P. Lobdell K. et al. Splanchnic and total body oxygen consumption differences in septic and injured patients. Surgery. 1987; 101: 69-80 PubMed Google Scholar Inadequate liver perfusion causes hepatocyte and Kupffer cell dysfunction interfering with the clearance of bacteria and their products. 4 Marick P.E. Gastric intramucosal pH: a better predictor of multiorgan dysfunction syndrome and death than oxygen-derived variables in patients with sepsis. Chest. 1993; 104: 225-229 Abstract Full Text Full Text PDF Scopus (285) Google Scholar The systemic inflammatory response syndrome with eventual end organ damage is the final outcome. Shock can usually be diagnosed at the bedside by hypotension, altered mental status, reduced urinary output, and lactic acidosis. More subtle organ ischemia, however, may go undetected. For some time, intensivists have searched for a measure of the adequacy of oxygen delivery at the cellular level. The Swan-Ganz catheter gives a rough estimate of global oxygen delivery, but it sheds little light on the adequacy of oxygen delivery to specific organs and cells. Gastric tonometry was developed in an attempt to diagnose occult gastrointestinal ischemia. 5 Clark C.H. Gutierrez G. Gastric intramucosal pH: a non-invasive method for the indirect measurement of tissue oxygenation. Am J Crit Care. 1992; 1: 53-60 PubMed Google Scholar A saline filled balloon inflated in the stomach is thought to be a tonometer that provides a reasonable estimate of the Pco2 in the wall of the stomach. This Pco2 and the arterial bicarbonate level are then used in the Henderson-Hasselbalch equation to calculate “intramucosal pH” (pHi). The utility and role of pHi in diagnosing gastrointestinal ischemia remains controversial.