Topical Bupivacaine Effect On The Response To Awake Extubation During Emergence From General Anesthesia
Condition: Thyroid Diseases
MeSH terms: Thyroid Diseases
Study type: Interventional

Summary: 
      -  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.
    

Detailed description: 
      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.
    

Intervention name(s): normal saline 0.9%; Bupivacaine Hydrochloride
Intervention type(s): Drug; Drug
Intervention description(s): 5ml of normal saline 0.9% topically 15 min will be installed topically around the ETT using ordinary syringe before the expected end of the surgery, this will be followed by manual ventilation using about the double tidal volume for 6-8 times or more to get air bubbles distributed within the upper airway to anesthetize the oropharynx and spread around ETT to the adjacent mucosal structures (laryngopharynx, larynx, and upper part of the trachea) then the cuff will be inflated to the previous pressure and the patient will be mechanically ventilated as usual.; 5 ml of bupivacaine 0.5% will be installed topically around the ETT using ordinary syringe before the expected end of the surgery, this will be followed by manual ventilation using about the double tidal volume for 6-8 times or more to get air bubbles distributed within the upper airway to anesthetize the oropharynx and spread around ETT to the adjacent mucosal structures (laryngopharynx, larynx, and upper part of the trachea) then the cuff will be inflated to the previous pressure and patient will be mechanically ventilated as usual.
Intervention MeSH terms: Bupivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: The patients will be divided randomly by a computer-generated randomization table into two equal groups
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: topical bupivacaine; awake extubation; thyroidectomy; general anesthesia