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CARDIOVASCULAR ANESTHESIA

Isoproterenol Enhances Myofilament Ca²⁺ Sensitivity During Hypothermia in Isolated Guinea Pig Beating Hearts

Yuri Nakae, MD PhD^*, Satoshi Fujita, MD PhD, and Akiyoshi Namiki, MD PhD^*

*Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo, Japan; and Department of Anesthesia, Hokkaido Keiaikai Minami 1-jyo Hospital, Sapporo, Japan

Address correspondence and reprint requests to Yuri Nakae, MD, PhD, Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226-0509. Address e-mail to ynakae{at}mcw.edu

Isoproterenol is often required to treat acute left ventricular dysfunction during separation from cardiopulmonary bypass for cardiac surgery. We hypothesized that heart rate and intracellular Ca²⁺ concentration ([Ca²⁺]_i) homeostasis may be important factors when isoproterenol improves the cardiac function during hypothermia. Accordingly, we investigated the effect of isoproterenol on the cardiac functional variables, [Ca²⁺]_i, and myofilament Ca²⁺ sensitivity under spontaneous beating during hypothermia. Intact guinea pig hearts were perfused with a modified Krebs-Ringer solution (baseline) and Krebs-Ringer solution containing isoproterenol (1 nM) at 37°C, 32°C, and 27°C while all cardiac variables and [Ca²⁺]_i were recorded. Isoproterenol increased developed left ventricular pressure (LVP), maximum rate of increase in LVP, and coronary inflow at 27°C, and it also increased heart rate and maximum rate of decrease in LVP at each temperature (P < 0.05). Isoproterenol produced a leftward shift of the curve of developed LVP as a function of available [Ca²⁺]_i at 32°C and 27°C (P < 0.05), without changing available [Ca²⁺]_i. Isoproterenol improves the cardiac function, especially systolic ventricular function, by enhancement of myofilament Ca²⁺ sensitivity under spontaneous beating during hypothermia in intact guinea pig hearts.

IMPLICATIONS: Enhancement of myofilament Ca²⁺ sensitivity is involved in the improvement of cardiac function by isoproterenol under spontaneous beating during hypothermia.

This article has been cited by other articles:

				G. R. Stier and E. W. Verde The postoperative care of adult patients exposed to deep hypothermic circulatory arrest. Seminars in Cardiothoracic and Vascular Anesthesia, March 1, 2007; 11(1): 77 - 85. [Abstract] [PDF]

				R. P. Katra, E. Pruvot, and K. R. Laurita Intracellular calcium handling heterogeneities in intact guinea pig hearts Am J Physiol Heart Circ Physiol, February 1, 2004; 286(2): H648 - H656. [Abstract] [Full Text] [PDF]

				Y. Nakae, S. Fujita, and A. Namiki Modulation of Myofilament Ca2+ Sensitivity by {delta}- and {kappa}-Opioid Agonists in Intact Guinea Pig Hearts Anesth. Analg., March 1, 2003; 96(3): 733 - 739. [Abstract] [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