Cerebral haemodynamic tests in ventilated traumatic brain injured patients: A correlative study with intracerebral microdialysis and clinical outcome.

摘要

Cerebral haemodynamic status defined as cerebral vasoreactivity to carbon dioxide and pressure autoregulatory response, have been shown to be affected after traumatic brain injury (TBI) and correlate with the neurological condition and clinical outcome. Therefore, it is important to have a reliable method to determine the cerebral haemodynamic status in brain-injured patients. Blood flow velocity (BFV) measurement by transcranial Doppler ultrasonography (TCD) has been shown to give accurate indication of changes in cerebral blood flow (CBF). Transient hyperaemic response (THR) test with TCD measurement to assess the BFV response of middle cerebral artery to a brief compression of the ipsilateral carotid artery, provides a simple method for repeated assessment of the cerebrovascular autoregulatory reserve in brain injured patients. However, the test has not been validated systematically against classical assessment tests using TCD and gold standard CBF measurement.;The goal of intensive care management for TBI is to provide them with a favourable physiological and metabolic environment for recovery of the injured-compromised cells. The development of clinical intracerebral microdialysis has enabled documentation of the metabolic derangement that provides more understanding of the mechanism of brain damage. Continuous measurement of both neurochemical and physiological parameters including CPP defined as mean arterial blood pressure (ABP) minus intracranial pressure, BFV and CBF, enables study of the relationship between metabolic events and physiologic changes. Clinical management of patients with TBI has emphasized on maintaining an optimal cerebral perfusion pressure (CPP). This critical CPP can then be defined by TCD, CBF as well as the metabolic measurements.;The aims of this thesis are (1) to validate the non-invasive TCD and its haemodynamic tests with a more involved gold standard CBF measurement using stable xenon-enhanced computerized tomography. (2) To correlate the cerebral haemodynamic abnormalities with the patterns of neurochemical disturbance detected by intracerebral microdialysis. (3) To investigate the possibility to reverse or minimized the cerebral haemodynamic abnormalities and metabolic derangement by treatment. (Abstract shortened by UMI.)