Microvascular perfusion and resistance in extracorporeal cardiopulmonary bypass under hypothermia with high-dose narcotic anesthesia--animal model.

Microvascular perfusion of the liver, kidney (cortex and medulla), pancreas and spleen was measured by laser-Doppler flowmetry under hypothermia in extracorporeal cardiopulmonary bypass, to determine the effectiveness of high-dose fentanyl in improving the microcirculation of these visceral organs. Twenty-four mongrel dogs in two groups were monitored by arterial catheter, Swan-Ganz catheter and laser-Doppler flowmeter. Cardiopulmonary bypass was carried out to induce hypothermia to 20 degrees C through the cannulation of inferior vena cava and aorta. Microvascular perfusion was measured by either needle or suturable probes of laser-Doppler flowmeter in liver, kidney (cortex and medulla), pancreas and spleen. With high-dose of fentanyl (100 micrograms/kg), decrease of microvascular perfusion in liver, pancreas and kidney (cortex and medulla) was less than the control group, especially at 20 degrees C. Notably, the trend of these changes had its unique pattern in each organ due to their own specific anatomical and physiological characteristics, while spleen did not show significant difference in both groups. In summary, high-dose of fentanyl improved the hepatic, renal and pancreatic microvascular perfusion, in agreement with our previous observation, might protect the function of these visceral organs from the damage of microvascular ischemia under hypothermia in the extracorporeal cardiopulmonary bypass.