Background and objective Serum hyaluronate is thought to be an indicator of derangement in hepatocellular integrity, and the change in serum hyaluronate is a useful indicator in various liver disorders. We assessed the changes in serum hyaluronate in patients undergoing coronary artery bypass graft surgery. Methods Eleven patients scheduled for elective coronary artery bypass graft surgery were studied. An oximetry oxygen saturation catheter was inserted into the right hepatic vein to permit monitoring of hepatic venous oxygen saturation. Perioperative measurements included: haemodynamic variables; systemic oxygen delivery and uptake; arterial, mixed venous and hepatic venous oxygen saturation; arterial and hepatic venous plasma concentrations of lactate, arterial ketone body ratio (ratio of acetoacetate to 3-hydroxybutyrate); and arterial and hepatic venous hyaluronate were measured. Results Arterial and hepatic venous hyaluronate increased during cardiopulmonary bypass compared with the prebypass period. These increases returned to prebypass values after the cessation of bypass (hepatic venous hyaluronate value at the prebypass period: 26 13 ng mL ±1 , during bypass: 77 40 ng mL ±1 ; 1 h after bypass: 57 42 ng mL ±1 ; 6 h after bypass: 32 15 ng L ±1 , 24 h after bypass; 62 21 ng mL ±1 ; mean SD, P < 0.05). The arterial and hepatic venous hyaluronate during cardiopulmonary bypass was correlated with total bilirubin and hepatic venous lactate concentrations 6 h after bypass (arterial hyaluronate at cardiopulmonary bypass period vs. total bilirubin at 6 h after bypass; r 0.793, P 0.0036, hepatic venous hyaluronate during bypass vs. that at 6 h after bypass; r 0.795, P 0.0035). Conclusions Hepatocellular integrity might be disturbed during cardiopulmonary bypass when propofol anaesthesia is used.