Blood–Brain Barrier Function Following Drug-induced Hypotension in the Dog

Abstract

To examine the effects of hypotension induced either with trimethaphan (TMP) or nitroprusside (NTP) on blood-brain barrier (BBB), penetration of [the protein-bound dye] Evans blue (EB) was observed in dogs anesthetized with halothane. Dogs given TMP were divided into 2 groups: group 1, 7 dogs were rendered hypotensive to mean cerebral perfusion pressure (CPP) of 45 mm Hg for 45 min and then of 30 mm Hg for 45 min; group 2, 3 dogs were examined 3 days after arterial hypotension identical to that in group 1. Dogs given NTP were divided into 4 groups: group 1, 7 dogs were rendered hypotensive with NTP (at dose < 1 mg/kg) identical to the TMP-group 1; group 2, 3 dogs were examined as the TMP-group 2; group 3, 7 dogs were rendered hypotensive to CPP 45 mmHg for 45 min; group 4, 7 dogs were rendered hypotensive with NTP (at dose > 1 mg/kg) identical to the NTP-group 1. In all dogs, the dorsal cortical surface and standardized serial coronal sections were examined for evidence of EB penetration. The mean EB penetration score (.+-. SEM [standard error of the mean]) for TMP-groups 1 and 2 was 12 .+-. 6, 0 .+-. 0, respectively, and for NTP-groups 1, 2, 3 and 4 was 105 .+-. 14, 30 .+-. 7, 6 .+-. 6, and 125 .+-. 26, respectively. Apparently, dysfunction of the BBB in the NTP group was more pronounced than in the TMP group.