Hepatic, renal, and cerebral tissue hypercarbia during sepsis and shock in rats

Earlier observations had indicated profound increases in the carbon dioxide tension of the myocardium, gastric wall, liver parenchyma, and renal cortex in the setting of extreme low-flow states of cardiac arrest and resuscitation, hemorrhagic shock, and anaphylactic shock. In venous blood draining the intestines, kidneys, and pelvic viscera, significant increases in PCO2 have also been observed during septic shock. In the present study, we investigated hepatic, renal, and cerebral cortical tissue carbon dioxide tension during intra-abdominal sepsis and shock in Sprague-Dawley rats. Peritonitis was induced by cecal ligation and fecal spillage. Over an interval of 320 +/- 60 minutes, we measured progressive reduction in mean aortic pressure from 152 +/- 11 mm Hg to 25 +/- 8 mm Hg and a decline in cardiac index from 492 +/- 75 ml/kg/min to 169 +/- 57 ml/kg/min. These hemodynamic deficits were accompanied by increases in liver tissue PCO2, from 58 +/- 4 mm Hg to 110 +/- 27 mm Hg (p = 0.006), in renal tissue PCO2, from 38 +/- 7 mm Hg to 115 +/- 24 mm Hg (p < 0.001), and in cerebral cortical tissue CO2, from 59 +/- 6 mm Hg to 108 +/- 16 mm Hg (p = 0.001). Arterial blood lactate content increased from 0.8 to 5.26 +/- 0.2 mmol/L (p = 0.001). Increases in blood lactate content preceded the changes in tissue PCO2 in each of these organs. These studies demonstrate that tissue hypercarbia is a more general phenomenon of low flow states, including that of circulatory shock associated with septic peritonitis.