Optimal cerebral perfusion pressure: are we ready for it?

Cerebral perfusion pressure (CPP)-oriented therapy and the Lund concept lie on opposite ends of the CPP scale, in the management of head injury. Optimization of CPP by monitoring cerebral vascular pressure reactivity is an alternative approach that may reconcile these two divergent approaches, preventing both injurious hypotension and hypertension with an individualized CPP target.

Indices describing cerebral vascular reactivity or cerebral blood flow autoregulation, derived from intracranial pressure, near-infrared spectroscopy, or transcranial Doppler are reviewed in this manuscript.

Indices of cerebrovascular reactivity and autoregulation typically converge to a U-shape curve when viewed as a function of CPP, with the best reactivity metrics indicating optimal CPP. In a retrospective study of prospectively collected data from head-injured patients, Steiner et al. demonstrated that a greater distance between averaged over total monitoring time-CPP and optimal CPP, correlated with unfavourable outcome. A recent study of 300 head-injured patients (2003-2009) showed that hypotension below optimal CPP was associated with greater mortality rate, while hypertension above optimal CPP was associated with an increase in severe disability.

Pilot studies indicating feasibility of autoregulation-oriented CPP optimization have been performed in adult and paediatric traumatic brain injury, aneurysmal subarachnoid haemorrhage, and in patients undergoing cardiothoracic surgery. It remains to be prospectively demonstrated whether optimal CPP management is able to improve outcome.