Changes in somatosensory evoked potentials and local cerebral blood flow rate in experimental subarachnoid hemorrhage.

ABSTRACT:Cerebral blood flow (CBF) and central conduction time (CCT) were recorded from 58 subarachnoid hemorrhage patients and from 49 age-matched controls. CBF was calculated following Xenon inhalation and CCT was determined from somatosensory evoked potentials (SSEP's) following median nerve stimulation. Each patient had a CT scan on the day of admission which was graded from I-IV. CBF, CCT and neurological grade (Hunt and Hess classification) were concomitantly recorded 1, 4, 7 and 14 days after subarachnoid hemorrhage. Mean CBF was highest in patients with neurological grades I and II (48.6 ± 12.3 and 48.1 ± 10.3 ml/lOOgm/min respectively) and lowest in patients with neurological grade IV (37.3 ± 9.6 ml/lOOgm/min). Patients in neurological grade I or II had mean CBF and CCT measurements that were significantly different from those obtained from patients in neurological grade IV (P < 0.05). Neurological grade and CT scan grade correlated with CBF (P < 0.0001) better than CCT (P = 0.015). Unexpectedly low CBF's from patients in neurological grades II and III (< 37 and < 31 ml/lOOgm/min respectively) failed to significantly prolong CCT suggesting CCT is unable to detect marginal ischemia. A significant correlation between CBF and CCT occurred only when CBF was < 30 ml/lOOgm/min (R = 0.75, P = 0.05). It appears that prolonged CCT is associated with a drop in CBF only when CBF drops below a certain threshold.

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Changes in local cerebral blood flow following profound systemic hypotension

Journal of Neurosurgery ◽

10.3171/jns.1976.44.2.0215 ◽

1976 ◽

Vol 44 (2) ◽

pp. 215-225 ◽

Cited By ~ 14

Author(s):

Francis W. Gamache ◽

Ronald E. Myers ◽

Esteban Monell

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Flow Rate ◽

Rank Order ◽

Blood Flow Rate ◽

Rapid Onset ◽

Border Zone ◽

Local Cerebral Blood Flow ◽

Content Type ◽

The Brain

✓ The authors studied local cerebral blood flow in monkeys rendered hypotensive by infusion of a ganglionic blocking agent. Application of the 14C-antipyrine method demonstrated that the blood flow: 1) normally varies reproducibly from one structure to another within the brain; 2) appears at its lowest level in all structures during the early minutes of a rapid-onset hypotension; 3) maintains the same general rank order of blood flow rate during hypotension as was present during normotension; and 4) returns to supranormal levels immediately following the rapid restoration of blood pressure. The values for local cerebral blood flow remain close-to-normal in some animals and diminish significantly in others during late recovery from hypotension. The close-to-normal values accompany uncomplicated recoveries while the diminished values appear in those animals which became neurologically depressed. Areas of the brain considered predisposed to hypotensive injury did not exhibit depressions in blood flow rate during hypotension more markedly than did other brain areas. The present results are interpreted as strong evidence against the “border zone” hypothesis.

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