Intracranial pressure changes following primate subarachnoid haemorrhage

Area of Science:

• Neurology
• Neurosurgery
• Physiology

Background:

• Subarachnoid hemorrhage (SAH) is a critical condition affecting cerebral hemodynamics.
• Understanding the immediate physiological responses to SAH is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the effects of induced intracranial arterial avulsion and subsequent subarachnoid hemorrhage on cerebral perfusion pressure and intracranial pressure in a closed-skull baboon model.
• To analyze the systemic circulatory responses and the occurrence of differential intracranial pressures following SAH.

Main Methods:

• Subarachnoid hemorrhage was induced via avulsion of a small intracranial artery in 29 anesthetized baboons.
• Intracranial pressure (ICP) was monitored using extradural transducers.
• Systemic arterial pressure and cerebral blood flow were measured continuously.

Main Results:

• An immediate significant fall in cerebral perfusion pressure (CPP) was observed in most animals post-hemorrhage, reaching zero in 9 cases.
• A systemic pressor response occurred in 18 animals, but CPP remained low.
• Differential ICP was noted in 11 of 19 cases, with higher pressure ipsilateral to the hemorrhage, often appearing rapidly and persisting.
• Arrest of bleeding was not primarily mediated by zero perfusion pressure.

Conclusions:

• The study highlights the complex and often inadequate physiological responses to SAH, characterized by initial CPP reduction and persistent differential ICP.
• The findings suggest that mechanisms other than complete pressure arrest are involved in hemorrhage containment.
• Further research is warranted to elucidate the mechanisms behind differential pressures and bleeding arrest in SAH.