Noninvasive estimation of cerebral perfusion pressure and zero flow pressure in healthy volunteers: the effects of changes in end-tidal carbon dioxide.

Unlabelled: Zero flow pressure (ZFP) in the cerebral circulation is defined as the arterial pressure at which flow ceases. Noninvasive methods of estimating cerebral perfusion pressure (CPP) and ZFP using transcranial Doppler ultrasonography have been described. There is a paucity of normal physiological data related to changes in estimated CPP (eCPP) and ZFP induced by changes in carbon dioxide (CO(2)).

A comparison of the transient hyperemic response test and the static autoregulation test to assess graded impairment in cerebral autoregulation during propofol, desflurane, and nitrous oxide anesthesia.

Unlabelled: The transient hyperemic response (THR) test has been used to assess cerebral autoregulation in anesthesia and intensive care. To date it has not been compared with the static autoregulation test for assessing graded changes in cerebral autoregulation. We compared the two tests during propofol, desflurane, and nitrous oxide anesthesia.

The effects of nitrous oxide and oxygen on transient hyperemic response in human volunteers.

Unlabelled: The aim of this study was to determine the effects of breathing 100% oxygen or 50% nitrous oxide in oxygen on the indices of cerebral autoregulation derived from the transient hyperemic response (THR) test in human volunteers. Data were analyzed from nine healthy subjects. Middle cerebral artery (MCA) blood flow velocity (FV) was measured by transcranial Doppler ultrasound, and the THR test was performed using 10-s compression of the common carotid artery.

The effects of sevoflurane and nitrous oxide on middle cerebral artery blood flow velocity and transient hyperemic response.

Unlabelled: We studied the effects of sevoflurane, with and without nitrous oxide, on the indices of cerebral autoregulation (transient hyperemic response ratio and the strength of autoregulation) derived from the transient hyperemic response (THR) test. Twelve patients (ASA physical status I or II) aged 18-40 yr presenting for routine non-neurosurgical procedures were recruited. The middle cerebral artery blood flow velocity was continuously recorded using transcranial Doppler ultrasonography.

Factors affecting assessment of cerebral autoregulation using the transient hyperaemic response test.

The transient hyperaemic response in the middle cerebral artery blood flow velocity on the release of brief compression of the ipsilateral common carotid artery has been validated as an indicator of cerebral autoregulation. We evaluated, in three stages, the effect of experimental factors such as duration of compression of the common carotid artery and magnitude of the decrease in blood flow velocity during common carotid artery compression on the transient hyperaemic response. In stage 1, 13 healthy volunteers underwent six transient hyperaemic response tests each; two tests each for either 3, 6 or 10 s duration of compression of the common carotid artery.