Treatment targets based on autoregulation parameters in neurocritical care patients.

Abstract

This review summarizes the physiological basis of autoregulation-oriented therapy in critically ill patients, with a particular emphasis on individual targets based on parameters that describe autoregulation of cerebral blood flow. The concepts of optimal cerebral perfusion (CPPopt) and arterial pressures (ABPopt), which both take advantage of continuous measures of cerebral autoregulation, recently have been introduced into clinical practice. It is hypothesized that if both pressures are used as individual targets and followed, the incidence and severity of dysautoregulation will diminish sufficiently to improve outcomes across the spectrum of acute neurological illnesses. These parameters have not been tested in randomized trials. However, a Phase II trial for CPPopt in Traumatic Brain Injury (COGITATE) is underway. Clinical series suggest that delirium following cardiac surgery may be reduced if blood pressure is actively regulated above the lower limit of autoregulation. In traumatic brain injury, using CPPopt as a single target allows monitoring of the upper and lower limits of autoregulation that provide a well tolerated 'corridor' for treatment. Pilot studies in which ABPopt is monitored in preterm newborns suggest fewer haemorrhagic events if blood pressure is closer to its optimal target. Brain imaging studies suggest worse tissue outcomes when blood pressure is below ABPopt. Targeted control of brain and systemic blood pressures to optimize cerebral autoregulation is of substantial interest to the neurocritical care and anaesthesia community, as this strategy may help to avoid secondary brain insults associated with ischemia or hyperaemia. The same strategy can be used outside the ICU (e.g. cardiac surgery, or in stroke patients after mechanical thrombectomy); this requires further research.