Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in common carotid blood flow (CCF) and resistance index (RI), calculated from velocity waveforms by a noninvasive pulsed Doppler technique, were measured during apneic episodes and voluntary breath holding in five sleep apnea patients (SA) and during breath holding in five normal subjects (N). During apneic episodes averaging 27 s, CCF was reduced by 9% and RI increased by 4%, both trends being related to apneic duration. Internal carotid artery measurements in one SA indicated more dramatic changes in blood flow and RI than noted in CCF. During breath holding, CCF decreased significantly in SA but not in N, and RI showed a smaller reduction in SA. These changes in CCF and RI during sleep apnea are similar to those noted in anesthetized dogs where vasomotor waves and associated apneas were induced by elevating intracranial pressure. Previously reported recordings of ventilatory and systemic cardiovascular responses in SA are similar to these recordings in dogs, and it is therefore proposed that vasomotor responses to intermittent cerebral ischemia and hypercapnia may be the principle event in SA and periodic breathing only a secondary consequence of the prevailing autonomic dysfunction.
 ...
PMID:Sleep apnea and autonomic cerebrovascular dysfunction. 310 21

Cerebrovascular reserve capacity (CVR) describes how far cerebral perfusion can increase from a baseline value after stimulation. Measurement of cerebral blood flow (CBF) can be done by PET or SPECT. Noninvasive and easily performed transcranial Doppler sonography (TCD) is mostly used as indirect perfusion measurement. Stimulation of cerebral perfusion is often done by CO2 inhalation or acetazolamide injection. Alternative stimuli are breath holding or cerebral activation by hand-gripping. Normal values for these tests are presented. The hemodynamic effect of stenoses of the internal carotid artery (ICA) can be estimated using CVR. The relevance of CVR is discussed controversially, since cerebral infarction due to stenosis of arteries supplying the brain is probably mostly of embolic, not hemodynamic origin. The indication for carotid artery surgery according the NASCET and ECST investigations takes into account only the degree of the stenoses and not the CVR. According to recent studies, the risk of cerebral infarction in these patients is considerably higher with reduced CVR. Therefore, CVR can be used as an additional parameter if the indication for surgery is not defined, especially in asymptomatic carotid artery stenosis. It seems also possible to identify patients who might profit from an extra-intracranial bypass operation and high-risk patients for cerebral ischemia with cerebral microangiopathy. Furthermore, the risk of cerebral infarction during carotid artery surgery and also during heart surgery can be estimated using CVR. More studies with a higher number of patients are needed to confirm the potential predictive diagnostic value of CVR in order to establish CVR measurement as part of a routine diagnostic neuroangiologic program.
 ...
PMID:[Cerebrovascular reserve capacity]. 1224 57