Reticuloendothelial function following cardiopulmonary bypass: laboratory and electron microscopy findings

Several studies on the effects of cardiopulmonary bypass (CPB) on the reticuloendothelial system (RES) function have been performed previously, but different results have been reported. This study was carried out to determine the effect of CPB on RES function in a canine model simulating clinical CPB. Nine dogs undergoing surgery with CPB were compared with an identical number of dogs subjected to thoracotomy without CPB. A lipid emulsion test was performed in all dogs before and after the surgical procedure to measure RES phagocytic index, i.e., phagocytic function. Kupffer cell iron uptake under conditions of iron loading following CPB was examined histologically, and any ultrastructural changes in the Kupffer cells were observed by electron microscopy. In both groups, the RES phagocytic index showed a significant decline after surgery. However, a comparison of the two groups revealed that there was a significantly greater decrease in the CPB group (P < 0.05). Moreover, histologic evidence of iron uptake in Kupffer cells was strongly suppressed in the CPB group. Electron microscopy of the Kupffer cells showed that the number of phagosomes, especially deformed erythrocytes, increased after CPB. These findings suggest that RES function is significantly impaired following CPB, and an increase in the amount of material, especially deformed erythrocytes, to be processed by the RES is responsible, in part, for the depressed RES phagocytic function. The prevention of hemolysis during CPB may preserve the RES function following CPB.