The Utility of Remifentanil Compared with Nitroglycerin for Deliberate Hypotensive Anaesthesia throughout Tympanoplasty. Randomized and Observer-Blinded Clinical Trial
Middle ear Haemostasis is considered special issue for the anesthetist because even minimal bleeding diminishes vision in surgical site, prolongs the surgical time and increases the complications. Deliberate hypotension can be accomplished by diminishing blood pressure at a lower level (40-50%) of its basal value or intentionally and reversibly diminishing mean arterial blood pressure (MAP) to 60 mmHg and maintaining it during surgery. Нere was a variety of methods and drugs that can be used for deliberate hypotensive anaesthesia such as calcium antagonists, vasodilators, beta blockers, or by using anesthetic agents like inhalational drugs, opioids and propofol . Adverse side eوٴects associated with these medications include the possibility of cardiac arrhythmia and myocardial depression, vasodilators resistance, potential cyanide toxicity as with sodium nitroprusside and delayed recovery. Perfusion of the vital organs is considered a special adverse eوٴect of deliberate hypotensive anaesthesia, additionally; eوٴective hypotensive medications have concentration-dependent adverse eوٴects which can be decreased by additive agents. Perfect hypotensive drugs have to be easy to use and prescription with a short onset and oوٴset time without toxic metabolites, have little or no side eوٴects on vital organs, and have expecting and dose-dependent adverse effects.
Remifentanil is powerful and highly selective opioid with ultrashort acting µ- receptor agonist which has short onset time of about 1 min, rapidly provides a stable condition, rapidly metabolized by blood and tissue nonspecific esterases enzymes with short elimination halflife less than 10 min that is independent of dose, time of infusion, renal or hepatic function. Additionally, it has moderate anti-hypertensive action without reflex tachycardia or rebound hypertension.Nitroglycerin (NTG) is directly acting as a vasodilator agent and provides deliberated hypotensive anaesthesia since it has a rapid onset time, be easily titrated and short time of elimination. But, it leads to increase heart rate (HR) and congestion at the operative field leading to increase bleeding.