2010 年 33 巻 2 号 p. 201-209
Objective: The intracranial pressure (ICP) monitoring has been recommended in Japan Society of Neurotraumatology (JSNT) Guidelines, and the cerebral perfusion pressure (CPP) oriented therapy has been performing to prevent the secondary ischemic brain damage in many institutions for the management of severe head injury. Although the optimal CPP value is recommended as over 60 – 70 mmHg in JSNT guidelines, there is no clear evidence. To determine the optimal CPP level in severely head-injured patients, the cerebral perfusion and brain metabolism were measured with microdialysis.
Methods: In severe head injury patients (GCS≦8), the value of ICP and CPP were monitored hourly for 7 days. Glucose, lactate, pyruvate, glycerol, and glutamate in dialysate were analyzed hourly with the microdialysis method. And the lactate/pyruvate (L/P) ratio which indicated the degree of ischemic brain damage was calculated in each case. Moreover, the values of these biochemical parameters were compared between groups divided by CPP value.
Results: The value of glucose was highest in the group of 71 – 80 mmHg of CPP group. The value of lactate, glycerol, and glutamate decreased according with the increasing of CPP value. When the CPP value decreased below 60 mmHg, the value of lactate, glycerol, and glutamate increased abruptly. These result suggests that the optimal CPP level seemed to be over 60 mmHg. However, with the evaluation of the optimal CPP value by analyzing the relationship between CPP and L/P ratio, the optimal value was different individually in each case. In addition, the pressure reactivity index (PRx) and the CPP/glucose slope, which should express the degree of impaired autoreguration, also varied in each case.
Conclusion: Our study suggested that the optimal CPP level is different in each case, and the variously impaired autoregulation is one of the factors which largely affect optimal CPP value. The direct monitoring of cerebral perfusion and brain metabolism with the microdialysis method might be useful to determine the optimal CPP levels in severely head-injured patients.
