Monitoring of cerebral autoregulation in head-injured patients

Background and Purpose Disturbed cerebral autoregulation has been reported to correlate with an unfavorable outcome after head injury. Using transcranial Doppler ultrasonography, we investigated whether hemodynamic responses to spontaneous variations of cerebral perfusion pressure (CPP) provide reliable information on cerebral autoregulatory reserve. Methods We studied 82 patients with head injury daily. Waveforms of intracranial pressure (ICP), arterial pressure, and transcranial Doppler flow velocity (FV) were captured during 2-hour periods. Time-averaged mean FV (FVm) and the FV during cardiac systole (FVs) were resolved. The correlation coefficient indices between FVm and CPP (Mx) and between FVs and CPP (Sx) during spontaneous fluctuations of CPP were calculated during 3-minute epochs and averaged for each investigation. Results Mx and Sx correlated with CPP (r=-.34,P=<.002; r=-.2, P=NS, respectively), with ICP (r=.46, P<.0001; r=.34, P<.003, respectively), with admission Glasgow Coma Scale score (r=-.34, P<.0025; r=-.38, P<.0008, respectively), and with outcome after head injury (r=.41, P<.0002; r=.48, P<.00009, respectively). In patients who died, cerebral autoregulation was severely disturbed during the first 2 days after injury. Conclusions Indices derived from spontaneous fluctuations of FV waveform and CPP describe cerebral vascular pressure reactivity. They correlate with outcome after head injury and therefore may be used to guide autoregulation-oriented intensive therapy.