BLOOD-BRAIN BARRIER PERMEABILITY (BBBP) FOLLOWING ASPHYXIA AND HYPOTENSION IN PIGLETS

Abstract

Asphyxia (A) and hypotension (H) may alter BBBP and cause cytotoxic edema in piglets (P). 2-4 day old spontaneously breathing P underwent A for 1 hour by exposure to 15% CO₂, 12% O₂ and balanced nitrogen resulting in pH=6.6±0.2, PaO₂=34±3mmHg and PaCO₂=70±6mmHg, M±SD. During the last 20 min of A, superimposed hemorragic H by phlebotomy (blood removed=30±9 ml/kg), resulted in a fall in mean arterial blood pressure to 29±10 mmHg. BBBP to ²⁴Na and ¹⁴C- mannitol was measured as the permeability X surface area product (PS). BBBP, brain water and brain electrolytes were determined 10 min (acute A&H) or 24 hours (post A&H) after A&H. Compared to age matched controls, A&H resulted in the following changes:

M±SD, ^*p<0.05 compared to age matched C, ND:not determined Brain water & electrolytes were similar in all groups. PS for ²⁴Na and M was decreased following acute A&H. Na/M values were similar in acute A & H vs C indicating a lack of change in the endothelial "pore" size. The decrease in PS may indicate a reduction in Na and M transport and/or more likely a reduction in brain endothelial capillary surface area.

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