Subcutaneous oxygen tensions provide similar information to ileal luminal CO2 tensions in an animal model of haemorrhage shock

Objectives: The cutaneous and splanchnic circulations undergo early vasocon striction in shock. Methodological problems and insufficient information on subcutaneous carbon dioxide partial pressures limit the usefulness of prev ious studies on splanchnic and subcutaneous gas tensions in shock. Little c omparative data exist on the responses of these tissues to shock and resusc itation. We therefore compared continuous subcutaneous PO2 (PO2sc) and PCO2 (PCO2sc) with simultaneous continuous gut luminal PCO2 (PCO2gi) in an anim al model of haemorrhagic shock and resuscitation. Design: Prospective observational study. Setting: Intensive care laboratory in a teaching hospital. Subjects: Five anaesthetised rats. Interventions: Electrochemical-fiberoptic gas sensors inserted into Silasti c tubing placed in the subcutaneous tissue and in the ileal lumen measured PCO2sc, PO2sc and PCO2gi continuously in five anaesthetised rats. After ste ady state conditions, hypotension [mean arterial blood pressure (MAP) 40 mm Hg] was induced by controlled haemorrhage. The rats were allowed to remain hypotensive for 15 min and then resuscitated with shed blood and crystalloi ds. Arterial plasma lactate concentrations were measured at defined periods during the study. Measurements and main results: Hypovolaemia resulted in a significant decre ase in PO2sc (P < 0.01) and a significant increase in PCO2gi and PCO2sc (P < 0.05). These values returned to baseline with resuscitation. PO2sc appear ed to respond to haemorrhage earlier than PCO2gi and PCO2sc (P = 0.02). PO2 sc was inversely correlated with PCO2gi (r(2) 0.7, P < 0.001). There were n o significant changes in arterial plasma lactate concentrations. Conclusions: In our rat model, subcutaneous oxygen tension provided similar information to ileal luminal PCO2 and was more rapidly responsive than sub cutaneous carbon dioxide tensions and arterial lactate during evolving haem orrhagic shock and resuscitation.