Background: Clinical investigations of brain death are supposed to prove absence of cerebral perfusion. However, only limited data are available documenting intracranial pressure (ICP) and cerebral perfusion pressure (CPP) during the development of brain death. Our study presents additional data to understand the course of ICP and CPP in patients developing brain death.
Material and methods: We analyzed retrospective data of 18 patients with ICP monitoring during the development of brain death due to primary brain lesions. ICP and CPP values were continuously measured between two clinically defined time points: 1. non-reactive and widened pupils, 2. brain death determination. We analyzed ICP and CPP at the above-mentioned end points. Additionally, we investigated maximum ICP and minimal CPP values between these time points.
Results: Patients developed fixed and dilated pupils with a median of 38 h before brain death determination. During brain death determination median ICP and median CPP were 103.5 and -2.5 mmHg, respectively. Maximum ICP before brain death determination was significantly higher and minimal CPP values were significantly lower compared to the time point of brain death. During the investigation period all patients experienced ICP values >95 mmHg and CPP < 10 mmHg. All but one patient had documented CPP values of ≤0 mmHg. This single patient had a minimum CPP of 8 mmHg with a maximum ICP of 145 mmHg.
Conclusion: Cerebral perfusion pressure during brain death determination may be positive in some patients. Our results showed variable values of ICP and CPP. However, extremely elevated ICP values before or during brain death in combination with low CPP values suggest absence of cerebral perfusion. The occurrence of positive CPP values during brain death determination therefore depends on the time point at which brain death determination is performed.
Keywords: Brain death; CPP; Fixed pupils; Herniation; ICP; Intensive care; Monitoring.
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