Cerebral arterial flow dynamics during aneurysm haemorrhage.

A case of intraoperative early rupture of an infraclinoid aneurysm is reported with data showing the specific dynamics of cerebral arterial flow during aneurysm haemorrhage. Internal carotid artery flow and arteriial blood pressure were recorded throughout the surgical procedure. The rupture took place during preparations for dural opening at a mean blood pressure of 160 mmHg and at a low intracranial pressure of 5 to 6 mmHg. The dura became instantly tight, and was non-pulsatile within 10 seconds. The parietal epidural pressure rose rapidly to 110 mmHg. There was a brief initial increase in flow as the haemorrhage started, followed by a marked reduction within seconds. End-diastolic blood flow arrest was observed at this stage, demonstrating the self-limiting effect of a subarachnoid haemorrhage. This impaired cerebral perfusion pressure, or transmural pressure, is discussed with regard to the risk of cerebral damage as well as the beneficial effect in the staunching of haemorrhage. Carotid artery flow showed a moderately impaired autoregulation and an increased vascular resistance suggesting a no-reflow phenomenon subsequent to these events.