Measurement of Regional Cerebral Blood Volume by Emission Tomography

“…where AI is brain 1'C radioactivity concentration, A2 is blood ~1C radioactivity concentration, CF is the factor used in the cross calibration of the Therascan PET scanner and the well counter used to measure ~1C radioactivity in blood samples, f is the ratio of the mean cerebral small-vessel hematocrit to large-vessel hematocrit (an average value of 0.85 has been used in this study 22 ), and dj and d2 are the densities of blood and brain, respectively (d~ = 1.05, dz = 1.05). 22 Baseline and post-mannitol infusion data were compared using paired t-tests with the Bonferroni method for muRiple comparisonY Values of t which yielded p < 0.05 were considered statistically significant.…”

Section: Discussionmentioning

confidence: 99%

Effects of rapid mannitol infusion on cerebral blood volume

Ravussin¹,

Archer²,

Tyler³

et al. 1986

Journal of Neurosurgery

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Positron emission tomography was used to study the effect of a rapid infusion of mannitol on cerebral blood volume (CBV) in five dogs and in three human subjects. The ability of mannitol to reduce intracranial pressure (ICP) has always been attributed to its osmotic dehydrating effect. The effects of mannitol infusion include increased osmolality, total blood volume, central venous pressure (CVP), and cerebral blood flow, and decreased hematocrit, hemoglobin concentration, serum sodium level, and viscosity. Mannitol's ability to dilate the cerebral vasculature, either directly or indirectly, and thus to transiently increase ICP, is a subject of controversy. By in vivo labeling of red cells with carbon-11, the authors were able to demonstrate an early increase in CBV in dogs of 20%, 27%, and 23% (mean increase, p less than 0.05) at 1, 2, and 3 minutes, respectively, after an infusion of 20% mannitol (2 gm/kg over a 3-minute period). The animals' muscle blood volume increased by 27% (mean increase, p less than 0.05) 2 minutes after infusion. In the human subjects, lower doses and a longer duration of infusion (1 gm/kg over 4 minutes) resulted in an increase in CBV of 8%, 14% (p less than 0.05), and 10% at 1, 2, and 3 minutes, respectively, after infusion. In dogs, ICP increased by 4 mm Hg (mean increase, p less than 0.05) 1 minute after the infusion, before decreasing sharply. The ICP was not measured in the human subjects. Hematocrit, hemoglobin, sodium, potassium, osmolality, heart rate, mean arterial pressure (MAP), and CVP were measured serially. Results of these measurements, as well as the significant decrease in MAP that occurred after mannitol infusion, are discussed. This study demonstrated that rapid mannitol infusion increases CBV and ICP. The increase in muscle blood volume, in the presence of a decreased MAP and an adequate CVP, suggests that mannitol may have caused vasodilation in these experiments.

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“…[5][6][7] Many studies have been conducted to evaluate hemodynamic and/or metabolic status in these patients, but the results are conflicting. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] We used positron emission tomography (PET) to assess the regional cerebral hemodynamics and metabolism in patients with severe symptomatic ICA stenosis before and after CEA.…”

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confidence: 99%