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NEUROSURGICAL ANESTHESIOLOGY

Central Hypervolemia with Hemodilution Impairs Dynamic Cerebral Autoregulation

Yojiro Ogawa, DDS, PhD^*, Ken-ichi Iwasaki, MD, PhD^*, Ken Aoki, PhD^*, Shigeki Shibata, MD, PhD, Jitsu Kato, MD, PhD, and Setsuro Ogawa, MD, PhD

From the Departments of *Hygiene and Space Medicine and Anesthesiology, Nihon University School of Medicine, Tokyo, Japan.

Address correspondence and reprint requests to Ken-ichi Iwasaki, MD, PhD, Associate Professor, Department of Hygiene and Space Medicine, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-Ku, Tokyo 173-8610, Japan. Address e-mail to kiwasaki{at}med.nihon-u.ac.jp.

Abstract

BACKGROUND: Frequent changes in the perioperative central blood volume could affect cerebral autoregulation through alterations in sympathetic nerve activity, cardiac output, blood viscosity, and cerebral vasomotor tone. However, the effect of dynamic cerebral autoregulation has not been studied during acute wide-ranging changes in central blood volume, especially with respect to central hypervolemia with hemodilution.

METHODS: We evaluated dynamic cerebral autoregulation during central hypovolemia and central hypervolemia with hemodilution using spectral and transfer function analysis between mean arterial blood pressure (MBP) and cerebral blood flow (CBF) velocity variability in 12 individuals. Rapid changes in central blood volume were achieved using two levels of lower body negative pressure (–15 and –30 mm Hg) and two discrete infusions of normal saline (15 mL/kg and total 30 mL/kg). We then estimated changes in central blood volume as central venous pressure (CVP) and/or cardiac output using impedance cardiography.

RESULTS: Steady-state CBF velocity and cardiac output decreased at –30 mm Hg lower body negative pressure (changes of CVP approximately –4 mm Hg) or were increased by each saline infusion (changes of CVP 4–6 mm Hg), without a significant change in MBP. However, transfer function gain (magnitude of transfer) between MBP and CBF velocity variability significantly increased only after saline infusion, suggesting an increased magnitude of transfer from MBP oscillations to CBF fluctuations during central hypervolemia with hemodilution.

CONCLUSION: Our results suggest that, although steady-state CBF velocity changes under both central hypervolemia and hypovolemia, only hypervolemic hemodilution impairs dynamic cerebral autoregulation.

This article has been cited by other articles:

				E. A. M. Frost Neurosurgical Anesthesia and Critical Care, Vol. 25, No. 3 in Anesthesiology Clinics Anesth. Analg., May 1, 2008; 106(5): 1595 - 1596. [Full Text] [PDF]

				J. K. Shoemaker Hemodilution Impairs Cerebral Autoregulation, Demonstrating the Complexity of Integrative Physiology Anesth. Analg., November 1, 2007; 105(5): 1179 - 1181. [Full Text] [PDF]

Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999