the use of patient data in the present report was approved by the institutional review board of seoul national university hospital ( registration number : 1603 - 149 - 751 ) . the need for informed consent
a total of 20 patients ( age , 2080 years ) , who were scheduled for thyroidectomy under local anesthesia with mac between december 2015 and february 2016 , were retrospectively reviewed .
electronic medical records including anesthetic , operative , nursing , and outpatient clinic records were reviewed .
exclusion criteria were communication barriers such as dementia , a language barrier , mental retardation , sternotomy , lateral neck dissection or multiple procedures , locally invasive cancer , morbid obesity , history of sleep apnea , claustrophobia , or an anxiety disorder .
after standard ( electrocardiography , noninvasive arterial blood pressure , and pulse oximetry ) and bispectral index ( bis ; vistatm monitoring system ; aspect medical systems inc . , norwood , ma , usa ) monitoring were applied , 3 l / min was delivered to patients through a nasal prong , and end - tidal co2 was monitored with this equipment .
all of the patients were administered 0.010.02 mg / kg midazolam during surgical dressing and draping .
propofol and remifentanil were delivered using a target controlled infusion ( tci ) pump ( orchestra module dps , fresenius kabi , langenhagen , germany ) with initial concentrations of 0.3 g / ml and 0.5 ng / ml , respectively .
the level of sedation was closely observed and targeted by bis between 7090 and a ramsey sedation scale ( rss ) score of 23 .
we increased or decreased the drug concentration by 0.2 g / ml or 0.2 ng / ml on the tci pump , according to the patient 's response , to obtain the target sedation level .
the patients underwent the surgery in a supine position without extending the neck or using a back roll . after preparing the skin and surgical draping ,
the operator directly injected 1012 cc of 2% lidocaine plus 1 : 100,000 epinephrine anesthesia around the incision line and the anterior field using a 22 gauge spinal needle .
after the planned surgery was finished , the sedative drugs were stopped , respiration and the rss were checked by an attending anesthesiologist , and the patient was delivered to the post - anesthesia care unit ( pacu ) .
patients were discharged from the pacu if they achieved a modified aldrete score  9 . the total amount of administered sedatives such as propofol , remifentanil , or midazolam ; desaturation ( spo2 < 95% ) ; unexpected movements , such as coughing , swallowing , respiratory or limb motions , which interrupted the surgical procedure ; and any other patient complaints were checked .
after the surgery , the surgeon and patient were asked if they were satisfied with the anesthesia on a 3-point scale ( bad - so so - good ) .
postoperative data were collected during hospitalization and at the outpatient clinic 12 weeks after discharge .
the incidence of postoperative nausea and vomiting ( ponv ) and the use of analgesics or antiemetics were also determined .
postoperative analgesics / antiemetics were administered when the patients complained of postoperative pain / nausea ( numerical rating scale > 5 ) or when they required these drugs .
treatments of 1 g propacetamol , 400 mg ibuprofen , or 0.075 mg palonosetron were intravenously administered for pain / nausea control .
postoperative complications were defined as more than one of the following conditions : ponv , sore throat , transient / permanent vocal cord paralysis , voice color change , hematoma , hypocalcemia , or wound problems .
table 1 shows the patient characteristics ; 2 of the 20 patients were excluded due to incomplete intraoperative electronic medical records .
the mean duration of surgery was 70.0  24.2 min , and the mean duration of anesthesia was 87.5  25.4 min ( table 2 ) .
median intraoperative bis was 80.5 ( interquartile range [ q1-q3 ] , 8094 ) , and the median rss score was 2 ( q1-q3 , 13 ) .
four desaturation events occurred intraoperatively , but the patients soon recovered with respiration encouragement or elevation of the mandible in the surgical field without mask bagging or additional airway management .
postoperative complications were evaluated during hospitalization and at the outpatient clinic follow - up ( table 3 ) .
no patient received analgesics while in the pacu , but five patients required pain control on the ward . according to the nurse 's records , four patients complained of sore throat during hospitalization .
symptomatic hypocalcemia occurred in one patient , which was medically corrected during hospitalization without subsequent complications .
transient voice color change was observed in one patient who had recovered by the follow - up examination .
the major advantages of general anesthesia are total loss of awareness , stable operative field , and a controlled airway .
however , general anesthesia prolongs postoperative recovery and can lead to hemodynamic instability during anesthetic induction .
in contrast , local anesthesia with mac results in a faster postoperative recovery , no throat or vocal cord irritation , and avoidance of muscle relaxant use . however , it can be challenging to control the sedation level to meet the surgeons ' and patients ' requirements and while simultaneously maintaining proper oxygenation .
the ideal properties of sedative agents include rapid onset , easy titration , high clearance , and minimal side effects , particularly a lack of hemodynamic impairment or respiratory depression . however , no definitive data are available for sedative drugs used during thyroidectomy under local or regional anesthesia .
snyder et al . , reported about patients who received local anesthesia with mac and boluses of midazolam , propofol , or fentanyl citrate for supplemental analgesia .
another study administered incremental doses of midazolam and fentanyl citrate to patients under mac with regional anesthesia only when required .
this single or repeated bolus technique can induce an unstable plasma / effect - site concentration , consequently leading to variability in sedation level and hemodynamic instability . to overcome this problem , we selected tci , which results in a stable concentration of sedative agent at the effect site , and for which the sedation level can be easily changed . in early cases , we set the initial target propofol and remifentanil concentrations to 1.0 g / ml and 1.0 ng / ml , respectively , during surgical draping , but recurrent desaturation events were observed at this concentration . a transient decrease in mean blood pressure ( mbp ) > 20% compared to baseline mbp simultaneously occurred in one case .
therefore , we decreased the initial target concentration after several cases and found that an effect - site propofol concentration of 0.31.5 g / ml and that of remifentanil of 0.51.0 ng / ml produced a satisfactory level of sedation without disturbing hemodynamic stability in the other cases .
caution is needed when increasing the concentration of sedative according to surgical stimulation , as a small titration is essential to cope with the inter - individual pharmacodynamic effects of each drug .
although it is difficult to directly compare with sedation protocols used for other procedures , hhener et al .   used a similar sedation protocol as our protocol under regional anesthesia ( propofol effect - site concentration of 0.40.8 g / ml and 0.51.0 ng / ml for remifentanil ) .
in addition , we added a 0.010.02 mg / kg midazolam bolus before draping or surgical incision to provide anxiolysis and mild amnesia .
accordingly , previous reports noted that low - dose midazolam with propofol improves patient comfort and quality of the sedation without delaying recovery and made the operation easier than using propofol alone during sedation .
recent reports have demonstrated that both of general and local anesthesia with mac can be used for thyroidectomy due to similar clinical outcomes , perioperative complications , and patient satisfaction . although no significant differences were observed in the number of nausea episodes between the general and local anesthesia groups , the general anesthesia group required more antiemetics than the local anesthesia group .
moreover , patients receiving local anesthesia with mac spent less time in the pacu and daycare center , leading to early discharge .
we did not compare our cases with thyroidectomy under general anesthesia , so we can not be certain that local anesthesia with mac is superior to general anesthesia during thyroidectomy .
however , the incidence of postoperative complications was similar to that of general anesthesia or local anesthesia with mac compared to previous studies . local anesthesia with mac allows patients to avoid the undesirable side effects and risks of general anesthesia . in this report
, a 37-year - old female patient with myasthenia gravis safely underwent a planned thyroid lobectomy under local anesthesia with mac , and was discharged without any discomfort or perioperative complications 1 day after the surgery .
the neurologist recommended local anesthesia or preparing for mechanical ventilation after general anesthesia during a preoperative work - up because of the possibility of delayed recovery from the effects of muscle relaxants .
other reports have demonstrated that patients with a family history of malignant hyperthermia or toxic amiodarone - induced hyperthyroidism have safely received thyroid surgery under local anesthesia .
in addition , intraoperative voice monitoring is possible in patients receiving local anesthesia with mac , which may make it preferable for patients with professional voice demands such as singers , vocal trainers , or teachers .
the need for local anesthesia combined with mac is rising with development of minimally invasive techniques in the field of thyroid surgery , particularly in outpatient settings .
however , candidates for thyroid surgery under local / regional anesthesia with mac must be chosen carefully . in a previous review ,
some absolute and relative contraindications were suggested to help with local / regional anesthesia for thyroidectomy . in their criteria , a communication barrier , a technically challenging operative procedure , patient refusal , and allergy to local anesthetic drugs were considered as absolute contraindications for local / regional anesthesia .
morbid obesity , sleep apnea , obscure anatomy , anticipated difficult intubation , prior neck surgery , and limited neck extension were relative contraindications ; however , these patients can be candidates for local anesthesia with mac on a case - by - case basis .
although we followed these classic criteria , selection criteria can be broadened over the course of increasing experience of the surgeon and anesthesiologist .
reported cases over 16 years and included patients with substernal goiter , extensive cancer , and morbid obesity in the last 5 years .
in addition , any possible intraoperative events beyond adjusting the sedation level should be known .
not only pain , but a vague awareness of being in the operation theater , sense of pulling and pressure on the surgical field , and fear of a blinding field of vision with surgical drapes can be irritating to patients .
on the other hand , the surgeon must contend with occasional motion of the operative field due to movements by the patient such as swallowing , coughing , or respiratory motion under local anesthesia with mac .
conversion to general anesthesia is occasionally required due to unanticipated lymphadenectomy , nerve sacrifice or injury , a change in the operative plan due to local invasion of a tumor , patient discomfort / anxiety , or long duration of the procedure . having a prior consultation or conversation among the surgeon ,
patient and anesthesiologist might help the surgeon can be accustomed to those intraoperative incidents of sudden motion , the patient can understand and endure the minor discomfort , and the anesthesiologists can prepare the rapidly changing condition of operative field or patients .
however , we could not fully demonstrate whether local anesthesia with mac for thyroidectomy is superior to general anesthesia .
our case report neither had a sufficient number of subjects to make a definitive recommendation on this topic nor had a control group , but rather shows the possibility of this new anesthetic approach for thyroid surgery .
the positive experiences from this case report offer pilot data or a clinical protocol for further investigation of thyroidectomy under local anesthesia with mac . in conclusion ,
thyroid surgery in selected patients can be performed safely using local anesthesia with mac by experienced surgeons and anesthesiologists and may be a simple and reasonable alternative to general anesthesia .
 because the current trend favors minimally invasive surgery for thyroid disease , increasing interest has developed for thyroidectomy under local anesthesia with monitored anesthesia care ( mac ) . here 
 , we retrospectively reviewed 18 cases of thyroidectomy performed under local anesthesia with mac in a single center . 
 all of the procedures were performed by a single surgeon , using local lidocaine infiltration around the incisional site and propofol plus remifentanil target - controlled infusion . 
 sore throat ( 4/18 ) , hypocalcemia ( 1/18 ) , and transient voice color change ( 1/18 ) were observed , but the patients recovered during the follow - up period . 
 no cases of postoperative nausea and vomiting , hematoma , wound problems , or vocal cord paralysis were observed . local anesthesia with mac provided satisfactory sedation in most patients without conversion to general anesthesia . 
Case Report
Discussion