Best Abstract Price to researcher from the Interventional Centre

Anesthesiologist and PhD student Søren Pischke was awarded an Abstract Price at the 2009 Autumn Meeting of the Norwegian Anesthesiology Society. The abstract describes researh work performed at the Interventional Centre and is presented here: Hepatic and intestinal PCO2 measurement for real-time detection of hepatic artery and/or portal vein occlusion.
Liver ischemia is a potentially life-threatening condition occurring in the course of liver transplantation, liver surgery and circulatory shock. Following liver transplantation hepatic artery (HA) stenosis and portal vein (PV) obstruction occur in 3 – 12 % of the patients, and more frequently in children than adults. Today, standard of care is Doppler ultrasound and liver enzyme assessment daily. Accordingly, detection of severe hypoperfusion may be delayed. Continuous monitoring of intrahepatic and intestinal PCO2 may be an opportunity for early detection of ischemia as tissue CO2 increases during ischemia by HCO3 buffering anaerobically produced lactic acid.
Blood flow reduction in either HA, PV or both leads to alterations in intermediary metabolism in the liver. Intrahepatic and intestinal CO2 measurement as a marker for anaerobic metabolism detects these changes and enables correct diagnosis of the affected vessel.

In ten pigs inflatable vascular occluders and ultrasound devices measuring blood flow were placed around the HA and PV. Blood sampling catheters were placed in the PV, hepatic vein and carotid artery. IscAlert™ (diameter < 1 mm) and Neurotrend® sensors measuring real-time PCO2 conductimetrically and PCO2, PO2 and pH optically, respectively, as well as microdialysis probes were placed in the liver. IscAlert™ sensors were placed between loops of small intestine reflecting intestinal PCO2 and microdialysis probes in the intestinal lumen. Subjects were assigned to either full occlusion of the HA and PV followed by gradual occlusion of both or to gradual occlusion of HA and PV followed by total occlusion of both.

Gradual as well as full occlusion of HA and PV led to significant increases of intrahepatic PCO2. This was accompanied by a significant decrease of PO2 and pH both intrahepatically and in the hepatic vein, but not in arterial blood. Microdialysis revealed minor elevation of lactate and glycerol during HA occlusion and significant elevation during occlusion of the PV or both. Intestinal PCO2 rose significantly upon occlusion of the PV accompanied by a significant rise of lactate and glycerol in the intestinal lumen.

Even a gradual occlusion of one vessel leads to detectable changes in liver metabolism. Intrahepatic PCO2 measurement reliably identifies these changes. Intestinal PCO2 increases only during PV occlusion, likely reflecting venous ischemia in the intestine. A combination of intrahepatic and intestinal PCO2 measurement reliably diagnoses the affected vessel, depicts the severity of the occlusion and emerges as a clinical tool enabling early intervention.