Middle cerebral O₂ delivery during the modified Oxford maneuver increases with sodium nitroprusside and decreases during phenylephrine.
Middle cerebral O₂ delivery during the modified Oxford maneuver increases with sodium nitroprusside and decreases during phenylephrine.
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改良牛津演习期间,中脑 O2 输送量随着硝普钠的增加而增加,而随着去氧肾上腺素的增加而减少。
DOI:
10.1152/ajpheart.00114.2013
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发表时间:
2013
期刊:
影响因子:
--
通讯作者:
Schwartz,ChristopherE
中科院分区:
文献类型:
--
作者:
Stewart,JulianM;Medow,MarvinS;DelPozzi,Andrew;Messer,ZacharyR;Terilli,Courtney;Schwartz,ChristopherE
The modified Oxford maneuver is the reference standard for assessing arterial baroreflex function. The maneuver comprises a systemic bolus injection of 100 μg sodium nitroprusside (SNP) followed by 150 μg phenylephrine (PE). On the one hand, this results in an increase in oxyhemoglobin and total hemoglobin followed by a decrease within the cerebral sample volume illuminated by near-infrared spectroscopy (NIRS). On the other hand, it produces a decrease in cerebral blood flow velocity (CBFv) within the middle cerebral artery (MCA) during SNP and an increase in CBFv during PE as measured by transcranial Doppler ultrasound. To resolve this apparent discrepancy, we hypothesized that SNP dilates, whereas PE constricts, the MCA. We combined transcranial Doppler ultrasound of the right MCA with NIRS illuminating the right frontal cortex in 12 supine healthy subjects 18–24 yr old. Assuming constant O2consumption and venous saturation, as estimated by partial venous occlusion plethysmography, we used conservation of mass (continuity) equations to estimate the changes in arterial inflow (ΔQa) and venous outflow (ΔQv) of the NIRS-illuminated area. Oxyhemoglobin and total hemoglobin, respectively, increased by 13.6 ± 1.6 and 15.2 ± 1.4 μmol/kg brain tissue with SNP despite hypotension and decreased by 6 ± 1 and 7 ± 1 μmol/kg with PE despite hypertension. SNP increased ΔQaby 0.36 ± .03 μmol·kg−1·s−1(21.6 μmol·kg−1·min−1), whereas CBFv decreased from 71 ± 2 to 62 ± 2 cm/s. PE decreased ΔQaby 0.27 ± .2 μmol·kg−1·s−1(16.2 μmol·kg−1·min−1), whereas CBFv increased to 75 ± 3 cm/s. These results are consistent with dilation of the MCA by SNP and constriction by PE.
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