Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is important to know the effects of anaesthetics on cerebral blood flow and cerebral metabolism to enable appropriate selection of agents for the brain injured patient. Thiopental possesses favourable cerebrovascular and metabolic properties but has not been shown to improve outcome in head injured patients. Propofol has properties similar to thiopental. Its rapid metabolism as well as its ability to reduce intracranial pressure and its antiemetic properties render it a very favourable drug. Despite controversies surrounding the effects of short-acting narcotics on intracranial pressure, they continue to be used because they provide stable haemodynamic conditions when used with care. Isoflurane is currently advocated as the best inhalational agent for neuroanaesthesia because of its lesser effects on cerebral blood flow and intracranial pressure. The effects of nitrous oxide on cerebral blood flow and intracranial pressure appear to vary according to the background anaesthetic used. Nitrous oxide is still widely used in most neuroanaesthetic practices, as its effects can be blunted by barbiturates, narcotics and/or hypocapnia. There is no convincing human study on the cerebral protective properties of anaesthetic agents although mild hypothermia has been shown experimentally to offer significant protection against global and focal ischaemia.
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PMID:Cerebrovascular and cerebral metabolic effects of commonly used anaesthetics. 771 Feb 26

We studied the mechanisms underlying CO(2)-dependent DC potential shifts, using epicranial, epidural, epicortical, intraventricular, and intraparenchymal (intraneuronal, intraglial, and field) recordings in ketamine-xylazine-anesthetized cats. DC shifts were elicited by changes in artificial ventilation, causing end-tidal CO(2) variations within a 2-5% range. Hypercapnia was consistently associated with negative scalp DC shifts (average shift -284.4 microV/CO(2)%, range -216 to -324 microV/CO(2)%), whereas hypocapnia induced positive scalp DC shifts (average shift 307.8 microV/CO(2)%, range 234 to 342 microV/CO(2)%) in all electrodes referenced versus the nasium bone. The former condition markedly increased intracranial pressure (ICP), whereas the latter only slightly reduced ICP. Breakdown of the blood-brain barrier (BBB) resulted in a positive DC shift and drastically reduced subsequent DC responses to hypo-/hypercapnia. Thiopental and isoflurane also elicited a dose-dependent positive DC shift and, at higher doses, hypo-/hypercapnia responses displayed reverted polarity. As to the possible implication of neurons in the production of DC shifts, no polarity reversal was recorded between scalp, various intracortical layers, and deep brain structures. Moreover, the membrane potential of neurons and glia did not show either significant or systematic variations in association with the scalp-recorded CO(2)-dependent DC shifts. Pathological activities of neurons during spike-wave seizures produced DC shifts of significantly smaller amplitude than those generated by hyper-/hypocapnia. DC shifts were still elicited when neuronal circuits were silent during anesthesia-induced burst-suppression patterns. We suggest that potentials generated by the BBB are the major source of epicortical/cranial DC shifts recorded under conditions affecting brain pH and/or cerebral blood flow.
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PMID:Nonneuronal origin of CO2-related DC EEG shifts: an in vivo study in the cat. 1505 89