The Viability Index: A survival score for perfusion patients

The Oxygen Pressure Field Theory predicts the development of a lethal corner (LC) within each capillary unit caused by a pathologic or iatrogenic reduction of perfused capillary density. The theoretical LC is defined by anoxic and/or hypercapnic tissues within individual capillary units. The LC configuration is theoretical, but tissues that are, for any reason, partially anoxic and/or hypercapnic can be detected using the corrected anion gap and the venoarterial carbon dioxide gradient of the blood. These two values are combined to yield a 'Viability Index' (VI). The VI is predictive of morbidity and mortality in patients prior to the initiation of extracorporeal support, can guide the perfusionist in designing a strategy that employs tactics more likely to result in a successful outcome among perfusion patients, and is helpful in assessing the status of patients whose vital signs are artificially sustained by extracorporeal perfusion support.