Session 2: Viability Index Scoring For Critical Cardiopulmonary and Extracorporeal Support Patients

The Hypercapnic Lethal Corner

The effect of shock and ischemia on the intracellular pCO2 of various organs.  Data complied from Johnson and Weil, 1991.

A meta-analysis published by Johnson and Weil demonstrates the effect of shock on intracellular pCO₂. Shock was initiated by hypoxia, reduced blood flow or absolute ischemia in the various experiments.  The baseline tissue pCO₂ averaged 50 mmHg, followed by a 3.6 fold increase to 188 mmHg during shock.  The pCO₂ increase is smaller in non-essential muscles, stomach and gut.  But, in essential organs such as the brain, kidneys and heart, the intracellular pCO₂ increase can be enormous. These experiments give some idea about the magnitude to which the intracellular CO2 concentration can rise during shock. However, this kind of direct assessment of intracellular pCO₂ in the clinical setting is impractical.  If tissue pCO₂ measurements could be made directly on specific organs such as the brain or heart, these would only reflect a local or regional effect.  The only practical method to assess intracellular pCO₂ is to measure the venoarterial CO₂ gradient as suggested by the Krogh model.