Dexmedetomidine Versus Lidocaine in Attenuating Airway Reflexes During Recovery of Thyroidectomy Patients

Intubation and extubation process are associated with cardiovascular and various airway responses leading to tachycardia, hypertension, arrhythmia, myocardial ischemia, cough induction, bronchospasm, increased bleeding, increased intracranial and intraocular pressure. Causes possibly include the presence of an endotracheal tube, uncleared secretions, and anesthetic gas. Furthermore, postoperative bleeding in thyroid surgery is still significant and is often associated with severe complications including cervical hematoma, reoperation and cardiac arrest. Extubation under deep anesthesia decreases cardiovascular stimulation and reduces the incidence of coughing and straining on the tube. Intratracheal local anesthetic instillation, I.V lidocaine, short acting opioids such as fentanyl and remifentanil, esmolol, labetalol, diltiazem and verapamil have been used to attenuate these hemodynamic and respiratory responses during extubation in the past but with certain limitations. Also "no stimulation" extubation technique avoids extubation under light anesthesia and ensures extubation only when consciousness is returned. It requires absolutely no stimulation during emergence and performing extubation only when the patient wakes up spontaneously and opens his eyes. Recently dexmedetomidine, a potent α2‐adrenoreceptor agonist has been used to facilitate extubation in surgical intensive care unit, but its role in the attenuation of hemodynamic and airway reflexes during extubation in general anesthesia is still under study. In this study the investigators are going to compare the effects of intravenous lidocaine and dexmedetomidine in inhibiting cough reflex during the recovery period after thyroid surgery.