Physiological Brain Monitoring

Several techniques are available for global and regional brain monitoring that provide an assessment of cerebral perfusion, oxygenation, and metabolic status, and early warning of impending brain hypoxia and ischemia (Supplemental Digital Content 1, http:// links.lww.com/ASA/A397). Some monitoring modalities are well established, whereas others are relatively new to the clinical arena and their indications are still being evaluated; all have advantages and disadvantages (Table 1). The general indications for intracranial monitoring are summarized in Table 2. Monitoring of several physiological variables simultaneously (multimodal monitoring) has enabled a move away from rigid physiological target setting to an individually tailored, patient-specific approach toward management after acute brain injury. The pathophysiology of acute brain injury is complex and involves the interrelation between changes in cerebral blood flow (CBF), cerebral oxygen and glucose delivery and utilization, and electrophysiological derangements, with substantial regional and temporal heterogeneity. Although intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are crucially important and are routinely monitored, they do not provide an assessment of the adequacy of cerebral perfusion. Therapeutic targets and choice of therapy are therefore best determined by multimodal monitoring.