Cerebral Perfusion Pressure Based Management of Traumatic Brain Injury

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Cerebral perfusion pressure (CPP) is the difference between mean arterial pressure (MAP) and intracranial pressure (ICP). Traditionally, management of traumatic brain injury (TBI) depended mainly on ICP control strategies. Based on the evidence that cerebral ischemia plays a major role in causing poor neurological outcome in traumatic brain injury (TBI) and cerebral blood flow autoregulation is shifted rightward in these patients, Rosner and colleagues suggested a treatment protocol that advocated maintaining a CPP higher than 70 mmHg, by controlling intracranial hypertension and increasing MAP by using hypervolemia and vasoactive agents, if required. Following the initial studies that showed better outcomes than other contemporary series, a number of studies tried to define the critical CPP in TBI. The threshold values suggested by these studies varied widely between 50 mmHg and higher than 70 mmHg. While there is no controversy about the adverse effects of low CPP, the major concerns in CPP-based therapy are a possible increase in brain oedema with a decrease in intracranial compliance and the systemic complications associated with the interventions used to achieve high CPP. There is no major evidence to suggest that high CPP increases ICP or decreases intracranial compliance. One major randomized trial comparing CPP-based and ICP-based strategies showed a major reduction in the incidence of cerebral ischemia with cerebral blood flow (CBF)-targeted therapy. But the same study also documented a five-fold increase in acute respiratory distress syndrome in patients managed by CPP-based strategy, and similar outcomes between the treatment groups. Following this, the brain trauma foundation (BTF) lowered the suggested CPP threshold to 60 mmHg from its original recommendation of 70 mmHg. Current research is focusing on the possibility of defining the optimal CPP for any given patient based on more objective measures of cerebral oxygenation, metabolism and CBF autoregulation. Critical thresholds of CPP in children remain ill-understood.