Hepatic artery (HA) occlusion and portal vein (PV) occlusion are the most common vascular complications after liver transplantation with an impact on mortality and retransplantation rates. The detection of severe hypoperfusion may be delayed with currently available diagnostic tools. Hypoperfusion and anaerobically produced lactic acid lead to increases in tissue carbon dioxide. We investigated whether the continuous assessment of the intrahepatic and intra-abdominal partial pressure of carbon dioxide (PCO2) could be used to detect and distinguish HA and PV occlusions in real time. In 13 pigs, the HA and the PV were fully occluded (n = 7) or gradually occluded (n = 6). PCO2 was monitored intrahepatically and between loops of small intestine. The hepatic and intestinal metabolism was assessed with microdialysis and PV as well as hepatic vein blood samples, and the results were compared to clinical parameters for the systemic circulation and blood gas analysis. Total HA occlusion led to significant increases in hepatic PCO2 and lactate, and this was accompanied by significant decreases in the partial pressure of oxygen and glucose. PV occlusion induced a significant increase in intestinal PCO2 (but not hepatic PCO2) along with significant increases in intestinal lactate and glycerol. Gradual HA occlusion and PV occlusion caused steady hepatic and intestinal PCO2 increases, respectively. Systemic clinical parameters such as the blood pressure, heart rate, and cardiac output were affected only by PV occlusion. In conclusion, even gradual HA occlusion affects liver metabolism and can be reliably identified with hepatic PCO2 measurements. Intestinal PCO2 increases only during PV occlusion. A combination of hepatic and intestinal PCO2 measurements can reliably diagnose the affected vessel and depict the severity of the occlusion, and this may emerge as a potential real-time clinical monitoring tool for the postoperative course of liver transplantation and enable early interventions. Liver Transpl, 2012. © 2012 AASLD.