Topical Bupivacaine Effect On The Response To Awake Extubation During Emergence From General Anesthesia
Topical Bupivacaine Effect On The Response To Awake Extubation During Emergence From General Anesthesia
-  Emergence from general anesthesia is often complicated by the ETT-induced emergence
 phenomena (EP), which include coughing, sympathetic stimulation, sore throat, increased
 bleeding from the surgical site, and increased intracranial and intraocular pressures.

 -  Techniques that have been used to help diminish coughing during emergence include "deep"
 extubation (removal of the endotracheal tube [ETT] while the patient is still in a deep
 plane of general anesthesia), administration of intravenous (IV) narcotics, or
 administration of IV lidocaine prior to emergence since systemic narcotics and lidocaine
 have antitussive properties. However, each of these techniques has limitations. A
 reliable technique for improving ETT tolerance while facilitating rapid and full
 emergence from general anesthesia would be desirable in many situations.

 -  Topical application of bupivacaine to the pharyngeal, laryngeal, and tracheal mucosa
 will attenuate or even abolish coughing as well as a hemodynamic response during
 extubation, thus result in increasing the patient's comfort and avoiding potential
 complications of extubation process.

 -  Up to the investigator's knowledge there is no study done to evaluate the effect of
 topical bupivacaine on the incidence of coughing and hemodynamic response during
 emergence from general anesthesia in patients undergoing elective thyroidectomy.
The process of manipulation of the airway during laryngoscopy, endotracheal intubation, and
 extubation is usually associated with exaggerated hemodynamic response including tachycardia,
 hypertension as well as increase intraocular and intracranial pressure[1,2]. The exact
 mechanism to these hemodynamic responses may be due to the release of catecholamine in the
 blood by stimulating the sympathetic nervous system during these stressful periods. Acute
 hemodynamic changes during extubation may lead to life-threatening myocardial ischemia,
 arrhythmias, pulmonary edema, acute heart failure, or cerebrovascular hemorrhage in high-risk
 patients and this can increase morbidity and mortality of the patients [3].

 Respiratory complications after tracheal extubation are three times more common than
 induction of anesthesia and intubation [4], as intratracheal tube induces laryngeal
 irritation that transmitted through rapidly acting receptors which are located throughout the
 trachea, involved in the cough reflex and subsequently lead to coughing and bucking that
 frequently occur during extubation and may lead to negative pressure pulmonary edema as well
 as, laryngeal edema and sore throat [5, 6].

 Various techniques have been applied to attenuate the hemodynamic responses and coughing
 during emergence and extubation. They include deep extubation, administration of intravenous
 (IV) short-acting narcotics, calcium channel blockers, and dexmedetomidine [7,8], as well as
 lidocaine which is considered one of the commonly used drugs either through IV route,
 endotracheal tube (ETT) cuff, or laryngotracheal route[1,9]. Concern about the use of these
 drugs includes respiratory depression, delayed emergence from anesthesia, postoperative
 nausea and vomiting, sedative effects, and short action time [10].

 Bupivacaine is a kind of sodium channel blocker local anesthetics used as topical anesthesia
 that suppresses cough by inhibiting the progression of the action potential in the tracheal
 touch-sensitive Aδ fibers (cough receptors)[10]. The plasma protein binding of bupivacaine
 exceeds 90%, whereas lidocaine protein binding is 65- 75%, [11] and it is well known that the
 duration of local anesthetics is influenced by their protein binding characteristics, as the
 affinity for plasma proteins corresponds to the affinity for protein binding at the sodium
 channel receptor site, that results in prolongation of the presence of the anesthetic effect
 at the site of action [12, 13].

 the investigators hypothesize that usage of topical bupivacaine may have an impact on
 decreasing incidence of coughing and alleviating hemodynamic response during awake extubation
 and emergence from general anesthesia in post-thyroidectomy patients.
Inclusion Criteria:

 Patient acceptance. BMI < 35kg/m2. ASA I and ASA II. Scheduled for elective thyroidectomy
 under general anesthesia

 Exclusion Criteria:

 Patient refusal. History or anticipated difficult intubation. Chronic respiratory disease
 such as chronic obstructive pulmonary disease or asthma.

 Recent respiratory tract infection in the last month, chronic cough, and current smoking.

 History of laryngeal or tracheal surgery or pathology. Patients with symptomatic gastric
 reflux. Patients with a known history of allergy to study drugs.