Use of thermography to predict intestinal viability and survival after ischemic injury: a blind experimental study

Reactive hyperemia is a characteristic of viable ischemic tissue that has been revascularized. In 14 normal dogs, segments of bowel were made ischemic for periods of 2--8 hours. Thermograms and surface temperature measurements of exposed ischemic and nonischemic segments were obtained before and every 5 minutes for 30 minutes after revascularization. Thermograms demonstrated uniform reactive hyperemia throughout the segments ischemic for 2--3 hours; hyperemia with some nonuniform, patchy areas in segments ischemic for 3--7 hours; and no hyperemic response in segments ischemic for 8 hours. All five dogs demonstrating uniform hyperemia survived and the bowels were found to be histologically normal. Four of the six dogs showing hyperemia with some nonuniform areas survived, but all six showed areas of transmural damage with fibrosis and scarring histopathologically. The three dogs with no hyperemic response died of pathologically proved bowel infarction. Our results indicate that thermograms can document the degree and extent of reactive hyperemia. Thermograms, therefore, may be an important aid in assessing bowel viability during surgery.