High-dose remifentanil increases blood pressure and heart rate mediated by sympatho-activation in conscious rats
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ORIGINAL ARTICLE
High-dose remifentanil increases blood pressure and heart rate mediated by sympatho-activation in conscious rats Tetsuro Shirasaka • Takeshi Yano • Takato Kunitake • Isao Tsuneyoshi
Received: 20 January 2012 / Accepted: 28 October 2012 / Published online: 7 November 2012 Ó Japanese Society of Anesthesiologists 2012
Abstract Purpose The ultra-short-acting l-opioid receptor agonist, remifentanil, is commonly used in clinical anesthesia; however, there are limited data about the hemodynamic effects of remifentanil itself without anesthetics. We investigated the effects of an ultra-short-acting l-opioid receptor agonist, remifentanil, on cardiovascular and sympathetic function in conscious rats. Methods The mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded during continuous intravenous (i.v.) infusion of remifentanil at a moderate-dose (0.25 and 0.5 lg/kg/min) and a high-dose (1.0 and 2.0 lg/kg/min) in conscious intact and sino-aortic denervated (SAD) rats. Baroreflex sensitivity was examined during remifentanil administration. Rats were administered saline or naloxone to assess the involvement of the l-opioid receptor in the remifentanilinduced responses. Results High-dose remifentanil induced biphasic changes in MAP and HR. Mediated by sympatho-activation, these parameters increased after briefly decreasing once. Subpressor-dose remifentanil enhanced baroreflex sensitivity. Changes in MAP, HR, and RSNA induced by remifentanil were inhibited by naloxone. Conclusions High-dose remifentanil decreases MAP and HR transiently and increases these parameters T. Shirasaka (&) T. Yano I. Tsuneyoshi Department of Anesthesiology and Intensive Care, Faculty of Medicine, University of Miyazaki, 5200 Kihara Kiyotake, Miyazaki 889-1692, Japan e-mail: [email protected] T. Kunitake Department of Integrative Physiology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan
mediated by the activation of sympathetic nerve activity in conscious rats. Keywords Remifentanil Opioid Sympathetic nerve activity Sinoaortic-denervated rats
Introduction Remifentanil is a relatively new, potent, and titratable ultra-short-acting l-opioid agonist [1]. Opioids and opiate receptors are located in specific brain nuclei known to regulate cardiovascular activity and to be involved in modulating sympathetic nervous system activity [2, 3] and baroreceptor reflex sensitivity [4]. Several studies have demonstrated that a combination of remifentanil and intravenous anesthetics has a dose-dependent cardiovascular depression with both bolus and continuous infusion [5–7]. Anesthesia is well known to profoundly affect the cardiovascular and autonomic nervous systems [8]. However, very few reports are available on the effects of remifentanil alone on the cardiovascular and sympathetic nerve activity (SNA) [9]. In this study, therefore, we investigated the effects of remifentanil on blood pressure (BP), heart rate (HR) and renal sympathetic nerve activity (RSNA)
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