Increased ileal-mucosal-arterial PCO2 gap is associated with impaired villus microcirculation in endotoxic pigs

Objective:To investigate whether an increased ileal-mucosal-arterial PCO2 g ap (Delta PCO2) during hyperdynamic porcine endotoxemia is associated with impaired villus microcirculation, Design: Prospective, randomized, controlled, experimental study. Setting: Animal research laboratory. Animals: Twenty-two domestic pigs. Interventions: After baseline measurements, anesthetized and ventilated pig s received continuous i.v. endotoxin (ETX, n = 12) for 24 h or placebo (SHA M, n = 10). Measurements and results: Before, as well as 12 and 24 h after, the start o f endotoxin or saline portal venous blood now (Q,v, ultrasound flow probe) and lactate/pyruvate ratios (LIP), the ileal-mucosal-arterial Delta PCO2 (f iberoptic sensor) and bowel-wall capillary hemoglobin Or saturation (%Hb-O- 2-cap, remission spectrophotometry) were assessed together with intravital video records of the ileal-mucosal microcirculation (number of perfused/het erogeneously perfused/unperfused villi) using orthogonal polarization spect ral imaging (CYTOSCAN A/R) via an ileostomy At 12 and 24 h endotoxin infusi on, about half of the evaluated villi were heterogeneously or unperfused wh ich was paralleled by a progressive significant increase of the ileal-mucos al-arterial Delta PCO2: and portal venous LIP ratios? whereas Q(PV) as well as both the mean % Hb-O-2-cap and the %Hb-O-2-cap frequency distributions remained unchanged. By contrast, in the SHAM-group, mucosal microcirculatio n was well-preserved, and none of the other parameters were influenced. Conclusions: We conclude that an increased ileal-mucosal-arterial Delta PCO 2 during porcine endotoxemia is related to impaired villus microcirculation . A putative contribution of disturbed cellular oxygen utilization resultin g from ''cytopathic hypoxia" may also assume importance.