Autoregulation

Autoregulation is the ability of an organ’s blood vessels to maintain a relatively constant blood flow despite changes in the driving blood pressure. When blood pressure rises or falls within a certain range, the vessels in the organ automatically constrict or dilate to compensate, keeping perfusion stable.

The brain has particularly powerful autoregulatory capacity. Cerebral autoregulation normally maintains stable brain blood flow across a mean arterial pressure (MAP) range of roughly 60 to 150 mmHg. Outside this range, blood flow becomes pressure-dependent: at very low pressures, the brain is underperfused; at very high pressures, it may be overperfused and at risk of oedema.

Autoregulation is critically important in the care of cardiac arrest survivors. After a period of cardiac arrest and resuscitation, the brain has often suffered hypoxic injury, and cerebral autoregulation may be impaired or lost entirely. This means the brain’s blood flow becomes entirely dependent on systemic blood pressure rather than self-regulated. In this state, maintaining an adequate blood pressure (via fluids, vasopressors, and careful monitoring) becomes essential to ensure the injured brain receives sufficient oxygen delivery during recovery.

Research in post-cardiac arrest care has explored whether autoregulation monitoring (using near-infrared spectroscopy or arterial pressure-based methods) can identify an optimal blood pressure target for individual patients, guiding critical care management and potentially improving neurological outcomes. This is an active area of clinical investigation. The coronary circulation and kidneys also have significant autoregulatory capacity, relevant to managing blood pressure and organ perfusion after arrest.