EVALUATION OF HEMODYNAMIC-RESPONSES IN HEAD-INJURY PATIENTS WITH TRANSCRANIAL DOPPLER MONITORING

Transcranial Doppler (TCD) can monitor middle cerebral artery (MCA) ve locity which can be recorded simultaneously with other physiologic par ameters such as end tidal (Et) CO2, arterial blood pressure and intrac ranial pressure (ICP), in head injured patients. Relative changes in M CA velocity can be used to reflect relative MCA blood flow changes dur ing ICP waves, and also to evaluate cerebral autoregulation, CO2 react ivity and hemodynamic responses to mannitol and barbiturates. The util ity and practicality of short intervals of TCD monitoring to evaluate hemodynamic resposnes, was evaluated in a group of 22 head injured pat ients (average Glasgow coma score 6). During ICP A waves, MCA velocity always decreased during the peak of the wave, and during ICP B waves, fluctuated synchronously with the ICP. Dynamic cerebral autoregulatio n,and reactivity to CO2, were reduced within 48 hours of admission. Im paired cerebral autoregulation within 48 hours of admission did not co rrelate with outcome at 1 month. Mannitol infusion caused an increase in MCA velocity (15.4 +/- 7.9%) which was significantly correlated to the impairment of dynamic autoregulation (r = 0.54, p < 0.0001). The M CA velocity response to a test dose of barbiturates was significantly correlated to the ICP (r=0.61, p<0.01) response as well as to the CO2 reactivity (r=0.37, p<0.05). Continuous MCA velocity monitoring using TCD may be useful in evaluating a variety of hemodynamic responses in head injury patients and may replace more cumbersome cerebral blood fl ow techniques which have been used in the past for these purposes.