Anaesthesia
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The role of vascular tone in determining cerebral perfusion pressure is increasingly being appreciated. It has been suggested that zero flow pressure, the arterial pressure at which blood flow ceases, represents the effective downstream pressure of the cerebral circulation. Nitrous oxide is a cerebral vasodilator and may therefore decrease zero flow pressure and increase cerebral perfusion pressure. ⋯ We studied eight healthy volunteers at normocapnia and studied the effects of the inhalation of nitrous oxide 50% on estimated cerebral perfusion pressure and zero flow pressure using transcranial Doppler ultrasonography. We found that nitrous oxide 50% significantly increased estimated cerebral perfusion pressure (p = 0.03), whilst decreasing zero flow pressure (p = 0.01). These results suggest that the vasomotor effects of nitrous oxide predominate in determining the effective downstream pressure of the cerebral circulation in healthy individuals.
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A survey of the members of the Neuroanaesthesia Society of Great Britain and Ireland was conducted to examine issues arising from the management of long cases. Replies were received from 47% of neuroanaesthetists. ⋯ These pressures are likely to increase as the European Working Time Directive reduces the availability of trainees, and because of expansion in neurosurgery and neuroradiology. Similar concerns are likely to extend into other anaesthetic specialties with long-duration cases and may apply to our surgical colleagues.
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Letter Case Reports
Incorrect assembly of non-return valve of an Oxylog ventilator.