الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Laryngoscopy and intubation are associated with cardiovascular changes such as hypertension, tachycardia, dysrhythmias and even myocardial ischemia, as well as increased circulating catecholamines and may lead to cerebral hemorrhage.
Several techniques have been proposed to prevent or attenuate the haemodynamic responses following laryngoscopy and intubation, such as deepening of anaesthesia, pretreatment with vasodilators such as nitroglycerin, beta-blockers, calcium channel blockers and opioids.
Labetalol, which has selective alpha-1-adrenergic and nonselective beta-adrenergic receptor antagonist properties, has been shown to blunt hemodynamic responses immediately following laryngoscopy and tracheal intubation and in the immediate postoperative period. The previous studies have indicated that low doses (10 mg or 0.14 mg/kg) of labetalol may blunt the HR response, while a high dose (1 mg/kg) attenuates both HR and BP responses to laryngoscopy and intubation at the expense of post intubation hypotension.
Dexmedetomidine is the dextro enantiomer of medetomidine, the methylated derivative of etomidine, its specificity for the alpha-2 receptor is 8 times that of clonidine, with an alpha-2:alpha-1 binding affinity ratio of 1620:1 and its effects are dose dependently reversed by administration of a selective alpha-2 antagonist such as atipamezole .
The mechanism of action of Dexmedetomidine is unique and differs from currently used sedative drugs, Presynaptic activation of alpha-2A adrenoceptor in the locus ceruleus inhibits the release of nor-epinephrine and results in the sedative and hypnotic effects, Stimulation of alpha-2 adrenoceptors in this area terminates the propagation of pain signals leading to analgesia. Postsynaptic activation of alpha-2 receptors in the CNS results in decrease in sympathetic activity leading to hypotension and bradycardia.
The aim of this study was to compare some haemodynamic response to laryngoscopy and tracheal intubation using intravenous labetalol versus intravenous dexmedetomidine in controlled hypertensive patients.
The study was carried out in Alexandria Main University Hospital on sixty patients, ASA class II, controlled hypertensive of both sexes, scheduled for elective surgery under general anaesthesia with endotracheal intubation.
Patients were categorized into three equal groups (20 patients each):
• Group I: Patients received 10 ml saline 0.9% and also 50 ml saline 0.9 % injected intravenously.
• Group II: Patients received 0.4 mg/kg labetalol diluted in 10 ml syringe and 50 ml saline 0.9 % injected intravenously.
• Group III: Patients received 1µg/kg dexmedetomidine diluted in 50 ml saline syringe and 10 ml saline 0.9 % injected intravenously.