Falling Intracranial Pressure: An Important Element in the Genesis of Intracranial Hemorrhage in the Beagle Puppy

Abstract

To study the role of extravascular intracranial pressure (ICP) in the genesis of intracranial hemorrhage in the beagle puppy, we measured ICP in animals on the day of birth, untreated 3-day-old controls, and 3-day-old animals treated from birth with prolactin. Baseline ICP varied substantially in all 3 groups. Only 8% of this variability was attributable to variability in mean arterial pressure and central venous pressure. ICP was lower in the 3-day-old controls, animals at high risk for intracranial hemorrhage after a hypovolemic/hypotensive insult followed by rapid volume expansion, than in the other groups which are at lower risk. Administration of a hyperosmolar insult, intraperitoneal glycerol, to animals whose ICP was relatively high promptly lowered ICP. After this treatment, the risk of intracranial hemorrhage was markedly increased in these previously low-risk groups. We conclude that the normal neonatal decrease in brain water content and the consequent fall in ICP substantially increase the risk of intracranial hemorrhage in the beagle puppy, a model which appears similar in pathophysiology to hemorrhage in the preterm human infant.