What does loss of normal cerebral auto-regulation after cardiac arrest depend on?

The loss of normal cerebral auto-regulation after cardiac arrest primarily depends on mean arterial pressure. Cerebral auto-regulation is the mechanism by which the brain maintains a constant blood flow despite fluctuations in systemic blood pressure. When a cardiac arrest occurs, the body's ability to maintain adequate blood pressure may be compromised, resulting in impaired cerebral auto-regulation.

In a healthy state, the brain can adjust its vascular resistance to maintain blood flow between a specific range of mean arterial pressures. However, after cardiac arrest, the mean arterial pressure may fall outside this range, leading to inadequate perfusion of brain tissue. This situation can critically influence the brain's ability to function and recover.

Other factors, such as intracranial pressure or heart rate variability, do not directly dictate the loss of this regulatory mechanism as prominently as mean arterial pressure does. While changes in cerebral blood volume might affect overall cerebral circulation, the immediate response related to cerebral auto-regulation centers on the pressures at which the brain is able to effectively receive blood supply.