Management of Arterial Blood Pressure

Acceptable blood pressure limits should similarly be agreed on at the beginning of a neurosurgical procedure. One of the prominent themes of contemporary neurosurgery is that CPP should be maintained at normal or even high-normal levels after acute central nervous system insults and during most intracranial neurosurgical procedures. This concept has evolved from the growing appreciation that CBF is frequently perilously low in some brain regions after acute neurologic insults, in particular, head injury (see additional discussion in the later section "Head Injury") and SAH. ^{[28] [38] [45]} Two additional factors should be considered. The first is that the autoregulatory response to decreasing blood pressure may not be intact throughout the brain. Figure 53-7 depicts the ischemic hazard that attends the circumstance of a low resting CBF and absent autoregulation even at blood pressure levels considered safe when autoregulation is intact. In addition, there is the appreciation that maintenance of arterial pressure is also relevant to brain compressed under retractors^[32] because the effective perfusion pressure there is lowered by increased local tissue pressure.

Although little other than anecdotal data support the notion, we believe that an aggressive attitude toward blood pressure support should be extrapolated to patients

Figure 53-7 Normal and absent autoregulation curves. The "absent" curve indicates a pressure-passive condition in which cerebral blood flow (CBF) varies in proportion to cerebral perfusion pressure. This curve is drawn to indicate subnormal CBF values during normotension as have been shown to occur immediately after both head injury^[28] and subarachnoid hemorrhage.^[45] The potential for modest hypotension to cause ischemia is apparent.