Hansen (A-56) notes that brain bilirubin concentrations are increased by hyperosmolality and hypercarbia, and that previous studies have not addressed the question of whether increased brain bilirubin under different conditions is due to effects on the entry into or clearance of bilirubin from brain. In a study, he hypothesized that the kinetics of increased brain bilirubin concentration would differ in respiratory acidosis (hypercarbia) and hyperosmolality. Forty-four young adult male Sprague-Dawley rats were sacrificed at various time periods following infusion with bilirubin.

The following are the blood bilirubin levelsð Þ mmol=L of 11 animals just prior to sacrifice 60 minutes after the start of bilirubin infusion:

Controls Hypercarbia Hyperosmolality 30 48 102 94 20 118 78 58 74 52 74 Source: Data provided courtesy of Dr. Thor Willy Ruud Hansen.