The effect of phenylephrine on arterial and venous cerebral blood flow in healthy subjects

• Published in: Clinical physiology and functional imaging Vol. 31; no. 6; pp. 445 - 451
• Main Authors: Ogoh, Shigehiko, Sato, Kohei, Fisher, James P., Seifert, Thomas, Overgaard, Morten, Secher, Niels H.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2011; Blackwell
• Subjects: Adrenergic alpha-1 Receptor Agonists - administration & dosage; Adult; Analysis of Variance; Arteries; Biological and medical sciences; Blood; Blood flow; Blood Flow Velocity - drug effects; Blood Pressure - drug effects; Carotid Artery, Internal - diagnostic imaging; Carotid Artery, Internal - drug effects; Carotid Artery, Internal - physiology; Cerebrovascular Circulation - drug effects; Denmark; frontal lobe oxygenation; Fundamental and applied biological sciences. Psychology; Humans; Imaging; Infusion; Infusions, Intravenous; internal carotid artery; internal jugular venous; Jugular Veins - diagnostic imaging; Jugular Veins - drug effects; Jugular Veins - physiology; Male; Middle Cerebral Artery - drug effects; Middle Cerebral Artery - physiology; middle cerebral artery mean blood velocity; near-infrared spectroscopy; Oxygen - blood; Oxygen Consumption - drug effects; Phenylephrine - administration & dosage; Physiology; Polyethylenes; Regional Blood Flow - drug effects; Spectroscopy, Near-Infrared; sympathetic nerve activity; Ultrasonography, Doppler, Color; Vasoconstriction; Vasoconstriction - drug effects; Vasoconstrictor Agents - administration & dosage; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Young Adult; Sympathetic nerve; Agonist; Frontal lobe; near-infrared spectroscopy; Central nervous system; Middle cerebral artery; α1-Adrenergic receptor; sympathetic nerve activity; internal jugular venous; Encephalon; Blood vessel; Phenylephrine; internal carotid artery; Human; Regional blood flow; Venous blood; frontal lobe oxygenation; Velocity; Arterial blood; Vertebrata; Mammalia; middle cerebral artery mean blood velocity; Carotid; α-Adrenergic receptor agonist; Circulatory system; Hemodynamics; Oxygenation
• ISSN: 1475-0961; 1475-097X; 1475-097X
• DOI: 10.1111/j.1475-097X.2011.01040.x

Summary Aim:  Sympathetic regulation of the cerebral circulation remains controversial. Although intravenous phenylephrine (PE) infusion reduces the near‐infrared spectroscopy (NIRS)‐determined measure of frontal lobe oxygenation (ScO2) and increases middle cerebral artery mean blood velocity (MCA Vmean), suggesting α‐adrenergic‐mediated cerebral vasoconstriction, this remains unconfirmed by evaluation of arterial and venous cerebral blood flow. Methods:  We determined ScO2, MCA Vmean, and right internal carotid artery (ICA) and internal jugular venous (IJV) blood flow (duplex ultrasound) during infusion of PE in eight supine young healthy men [26 (3) years, 177 (7) cm and 74 (8) kg; mean (SD)]. Results:  Compared with saline, during infusion of PE, mean arterial pressure increased 26 ± 3% (mean ± SE) and MCA Vmean by 4·8 ± 1·9% (P<0·05), while ScO2 decreased by 13·7 ± 3·7% (P<0·05) with no significant changes in the arterial oxygen or carbon dioxide tensions. ICA blood flow did not change significantly in response to PE administration (351 ± 12 versus 373 ± 21 ml min−1; P = 0·236), while IJV blood flow increased (443 ± 57 versus 507 ± 58 ml min−1; P = 0·023). Conclusions:  These findings confirm that PE induces a reduction in ScO2 measured by NIRS and causes an increase in MCA Vmean indicative of cerebral arterial vasoconstriction, although ICA was preserved and IJV increased. These results suggest that a decrease in ScO2 during infusion of PE reflects an altered cerebral contribution of arterial versus venous blood to the NIRS signal, although we cannot rule out that an effect of PE on skin blood flow is important.