Abstract
Although severe hypovolemia can lead to hypotension and neurological decline, many patients with neurosurgical disorders experience a significant hypovolemia while autonomic compensatory mechanisms maintain a normal blood pressure. To assess the effects of normotensive hypovolemia upon cerebral hemodynamics, transcranial Doppler ultrasound monitoring of 13 healthy volunteers was performed during graded lower-body negative pressure of up to -50 mm Hg, an accepted laboratory model for reproducing the physiological effects of hypovolemia. Middle cerebral artery flow velocity declined by 16% ± 4% (mean ± standard error of the mean) and the ratio between transcranial Doppler ultrasound pulsatility and systemic pulsatility rose 22% ± 8%, suggesting cerebral small-vessel vasoconstriction in response to the sympathetic activation unmasked by lower-body negative pressure. This vasoconstriction may interfere with the autoregulatory response to a sudden fall in blood pressure, and may explain the common observation of neurological deficit during hypovolemia even with a normal blood pressure.
Original language | English (US) |
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Pages (from-to) | 961-966 |
Number of pages | 6 |
Journal | Journal of neurosurgery |
Volume | 76 |
Issue number | 6 |
DOIs | |
State | Published - 1992 |
Externally published | Yes |
Keywords
- hypovolemia
- lower-body negative pressure
- sympathetic nervous system
- transcranial Doppler ultrasound
ASJC Scopus subject areas
- Surgery
- Clinical Neurology