Experimental intracranial hypertension following cisternal injection of various blood components.

Intracranial pressure (ICP) was recorded in 30 dogs which underwent cisternal injection of blood, serum, red blood cells (RBC). RBC ghosts, oxyhemoglobin or bilirubin. The amount of injection was 8-10 ml of blood or an equivalent volume of blood components. Blood or RBC showed a sustained ICP of 15 to 25 mmHg, and RBC ghosts caused a slight transient rise of ICP. In contrast, oxyhemoglobin or bilirubin induced marked intracranial hypertension up to 60-80 mmHg which was associated with frequent pressure waves. Histological examination disclosed aseptic meningitis at the base of the brain and inflammatory changes in the floor of the fourth ventricle after the injection of oxyhemoglobin or bilirubin. It is suggested that the breakdown products of RBC might be causative factors of the intracranial hypertension following subarachnoid hemorrhage.