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Anesth Analg 2000;91:140-144
© 2000 International Anesthesia Research Society

NEUROSURGICAL ANESTHESIA

Hypothermia Attenuates the Vasodilatory Response of Pial Arterioles to Hemorrhagic Hypotension in the Cat

Katsuyoshi Kishi, MD, Masahiko Kawaguchi, MD, Koukichi Kurehara, MD, Satoki Inoue, MD, Takanori Sakamoto, MD, Toshi Einaga, MD, Katsuyasu Kitaguchi, MD, and Hitoshi Furuya, MD

Department of Anesthesiology, Nara Medical University, Nara, Japan

Address correspondence and reprint requests to Katsuyoshi Kishi, MD, Department of Anesthesiology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. Address e-mail to kishi{at}sikasenbey.or.jp

We investigated the effect of hypothermia on the vasodilatory response of pial arterioles to hemorrhagic hypotension. The cranial window technique was combined with microscopic video recording in an experiment involving 20 cats anesthetized with pentobarbital. The animals were randomly assigned to either a normothermic or a hypothermic group (32°C). Mean arterial pressure (MAP) was reduced in stepwise increments of 10 mm Hg (from 100 to 50 mm Hg) by blood withdrawal. The diameter of small (50–100 µm) and large (100–200 µm) pial arterioles was measured. In the normothermic group (n = 9), small and large arterioles dilated at a MAP of 60 and 50 mm Hg, and at a MAP of 70, 60, and 50 mm Hg, respectively, compared with baseline values obtained at a MAP of 100 mm Hg. In contrast, in the hypothermic group (n = 11), vasodilation of either small or large arterioles was absent. The percentage diameter of small and large arterioles (percentage of control) was significantly lower at a MAP of 70, 60, and 50 mm Hg in the hypothermic group than the normothermic group. Our in vivo study demonstrates that hypothermia impairs autoregulatory vasodilation of pial arterioles in response to hemorrhagic hypotension.

Implications: Deliberate mild hypothermia has been proposed as a means of providing cerebral protection during neurosurgical procedures. Our results suggest that cerebral blood flow autoregulation in response to hemorrhagic hypotension may be impaired during hypothermic conditions, indicating the importance of maintaining perfusion pressure during hypothermic therapy to prevent cerebral ischemia.






Lippincott, Williams & Wilkins 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 HighWire Press
Copyright © 2000 by the International Anesthesia Research Society.