重症脳障害患者の連続的TCDモニタリングの意義―頭蓋内圧亢進, 脳虚血, 脳機能障害との関連から―

抄録

To clarify the significance of transcranial Doppler (TCD) monitoring for detection of raised intracranial pressure (ICP), cerebral ischemia, and neuronal dysfunction in comatose patients with severe brain damage, vasoreactive correlations during hyperventilation (HV) and changes in cerebral perfusion pressure (CPP) were evaluated by continuous monitoring of TCD in the middle cerebral artery, jugular bulb oxygen saturation (SjO₂), end-tidal CO₂partial pressure, ICP and CPP, and quantitative EEG (qEEG) . TCD and gEEG (total and spectral power bands) were monitored in a total of 32 cases of severe head injury, CPP in 26, and SjO₂in 16 for 7 days (mean) . Peak systolic, mean, and end-diastolic velocity (Vs, Vm, Vd), pulsatility index (PI), resistance index, and cerebrovascular resistance (CVR=CPP/Vm) were evaluated. a) CO₂reactivity (ΔVm/ΔCO₂, ΔSjO₂/ΔCO₂) and correlations with ICP and SjO₂were compared within ischemic, normal, and hyperemic groups, based on minimal SjO₂during HV. b) Effects of CPP changes were correlated with gEEG. a) HV: 1) No significant differences in TCD parameters and ΔVm/ΔCO₂were observed among the three groups. However, ΔSjO₂/ΔCO₂was significantly high in the order of ischemic>normal> hyperemic groups. 2) Close correlations of ICP with Vm and CVR were identified. 3) Significant correlations of SjO₂with CVR, Vm, Vs, and PI were observed frequently in the ischemic group. b) CPP: 1) In cases of close correlation between CPP (<60 mmHg) and Vm, there were significant correlations between all gEEG power bands and Vm. 2) Loss of gEEG was observed in four cases of Vm<36 cm/s, Vd=0, and PI>2.74. Continuous TCD monitoring is useful for the early detection of decreased cerebral circulation and increased CVR associated with intracranial hypertension, cerebral ischemia, and neuronal dysfunction, but not always for easy interpretation of the underlying pathophysiology in patients with severe brain damage.