HYPEROSMOLALITY(HO) AUGMENTED REGIONAL BRAIN BILIRUBIN DEPOSITION(RBBD) IN NEWBORN PIGLETS(P)

This study was designed to explore the mechanisms of previously shown enhanced bilirubin brain deposition in urea induced HO. 28 2-4 day old P were infused with bilirubin(B)to raise & maintain serum B(SB) to approximately 8mg/dl. 14 P served as isoosmotic controls(C),7 P received urea infusions to raise serum osmolality to 330mOsm//L(HO330)& 7 P to 375mOsm/L(HO375). During 60 min of HO, SB was similar among the 3 groups(7-9mg/dl). Serum unbound B(UB) was also similar between HO330&C. In contrast, UB was 2.7-fold higher in HO375 vs C(p<0.01). Microsphere measured regional brain blood flow(RBBF)was similar in cerebrum(CE), thalamus(TH),midbrain(MB),cerebellum(CB),& brainstem(BS)among the 3 groups. RBBD & brain albumin content(BA, 125-I-albumin) are:We conclude that marked HO(375mOsm/L) resulted in enhanced RBBD probably due to HO-related increase in UB & opening of the blood-brain barrier(BBB) to B. Furthermore, opening of the BBB to B may be more pronounced in the CE than in the other regions studied.