Discussion:
Anuwong (8) introduced transoral endoscopic surgery using conventional laparoscopic instruments via oral vestibule, through premandibular space with CO2 insufflation. First they used this approach in thyroidectomy patients (Transoral endoscopic thyroidectomy by vestibular approach:TOETVA). They reported that, TOETVA is safe and feasible, resulting in no visible scar thus ideal method for cosmetic results. In 2016, Sasanakietkul T, Jitpratoom P and Anuwong A [2] adapted Anuwong’s technique, which he introduced for TOETVA, to parathyroid surgery (primary hyperparatyrisidism or renal hyperparatyrisidism) using the inferior lip (Transoral endoscopic parathyroidectomy by vestibular approach:TOEPVA). They reported excellent cosmetic outcomes with feasible and safe surgical option.
While advances in surgical technique have been continued in parathyroid surgery, we have not been able to find recommendations regarding the anesthesia management of these cases in the literature. Up to date, there is no report is published about how we can manage these patients under general anaesthesia. Therefore, we want to share our anesthesia management in TOEPVA in the literature.
Transoral surgery can be considered as having three important stages in terms of anesthesia management. 1. Hydrodissection 2. Insufflations and 3. Surgical phase. While hydrodissection phase may cause an increase in sympathetic activity by diluated epinephrine solution used for hydrodissection; neck insufflations by carbon dioxide may cause sudden suppression of sympathetic activity. During the surgical phase, due to the surgical technique applied, absolute immobility of the case is very necesssary for anaesthetist and surgeon, to avoid serious events. The most important complications in surgical phase are pneumomediastinum and/or pneumothorax and recurrent laryngeal nerve injury which requires close capnography monitorisation and respiratuar follow-up respectively [9].
For the best management of all the phases that mentioned above, we preferred balanced anaesthesia (inhalation anaesthesia with opioid) in our anaesthesia management in TOEPVA. We preferred desflurane as inhalation anaesthetic; remientanil as opioid and rocuronium bromide as neuromuscular blocker. All patients were reversed by sugammadex and extubated at the end of the surgery. So in this article we want to explain why we preferred these agents in our anaesthesia management in TOEPVA.
Desflurane is a relatively new volatile anaesthetic, that have a low blood-gas solubility resulting in rapid uptake and elimination [10]. Its muscle-gas partition coefficient is lower than other volatile anaesthetics [11]. The enhancement of the neuromuscular blocking effects of muscle relaxants (both benzylisoquinoline and aminosteroid) by volatile anaesthetics is well known [11-13] and this phenomenon is called as “Potentiation” (10). Rocuronium bromide is a monoquaternary, aminosteroid, non-depolarising muscle relaxant with rapid onset and intermediate duration of action [10,13]. Sugammadex is a modified ɣ-cylodextrin developed for reversal of neuromuscular blockade induced by aminosteroid neuromuscular blocking agents, particularly rocuronium by formatting a complex with rocuronium (encapsulation). Previous meta-analysis results reported that sugammadex is superior to neostigmine, as it reverses neuromuscular block faster and more reliable and accelerates postoperative discharge of patients after general anaesthesia [14,15].
Wulf and colleagues [10] reported that neuromuscular blocking effect of rocuronium to be enhanced by sevoflurane and desflurane, compared with total intravenous anesthesia (TIVA) (propofol/fentanil). Bock and et [12] showed that there was a marked interaction between neuromuscular blocking effects of rocuronium and isoflurane, desflurane and sevoflurane, compared with propofol. Maidatsi et al [11] reported that desflurane anaesthesia significantly prolongs the duration of action of rocuronium, compared to sevoflurane or propofol anaesthesia in anaesthesia maintainance regimens. Although in vitro studies propofol has been reported to potentiate the effects of neuromuscular blockers; there is no report to date that propofol can clinically potentiate the the effects of neuromuscular blockers clinically [13].
While neuromuscular blockade should be intense peroperatively because of the nature of the surgery; maintainance of the airway patency must be supplied at the end of the surgery. So we preferred rocuronium as a neuromuscular agent, which has a specific and reliable reversal agent to manage airway patency uneventfully after extubation and desflurane as an inhalation agent, which enhances the neuromuscular block effect of rocuronium peroperativelly.
It is important to measure intraoperative PTH level to verify the removal of pathological parathyroid adenoma. PTH has a short half-time and rapid metabolic clearance rate and has a rapid assay. But on the other hand, PTH level influenced by some many factors including stress, stress hormones (such as catecholamines, cortisol and inulin), general anesthesia and endotracheal intubation (the most stress-baring procedure), calcium, magnesium, vitamin D, anesthetic agents (propofol) and laparoscopic surgeries (elevated blood CO2 may change blood pH and cause a shift of ionized calcium [15,16]. Also previous studies reported that propofol influence PTH level; Kivela et al results suggests that there is no need to avoid propofol during parathyroid surgery as previously suggested [16]. Whether propofol affects PTH level or not is still debate so we prefer inhalation anesthesia and desflurane as inhalation anaesthetic. We preferred propofol only during induction to prevent hemodynamic alternations to stress response and to suppress upper airway reflexes for nasal intubation.But Bacuzzi et al [9] suggest total intravenous anesthesia (bolus dose of propofol (2 mg/kg) followed by infusion (0.2–0.5 γ/kg/min) of remifentanil) for transoral approaches.
Opioids have an important influence on upper airway events, purposeful movements during surgery and recovery time [18], the requirements for propofol or volatile anaesthetics [18,19]. Remifentanil has rapid onset, short duration of action [18-20], great intraoperative analgesia [19-21], quick recovery time [19-21], excellent controllability [18] and metabolized by non-spesific esterase so elimination is independent from liver and renal [18,19]. But over-administered opioid analgesics during surgery delay recovery from anaesthesia and cause opioid related side effects [19,20].
Ryu et al [20] compared intraoperative remifentanil requirements during equi-Minimum Alveolar Concentration (MAC) anesthesia of 1 MAC sevoflurane and desflurane anaesthesia via surgical pleth index-guided remifentanil administration. They reported that intraoperative remifentanil consumption was significantly lower in desflurane group than sevoflurane group. Kowark and colleagues [18] shown that in the presence of a continous infusion of remifentanil, desflurane is significantly superior than sevoflurane and propofol in terms of emergence from anaesthesia. Fukunaga et al [22] and Nooh et al [19] showed same results. Remifentanil provides effective suppression of cardiovascular responses to surgical stimulation and promotes hemodynamic stability and improves recovery profiles.
We preferred remifentanil infusion as opioid analgesic to manage sempatic activity changes during hydrodissection and insufflations phase of anaesthesia in our anaesthesia management because of its best pharmacokinetics and pharmacodynamics properties. And also we believe that we lower intraoperative remifentanil consumption, avoid over administered opioid side effects and better emergenced from anaesthesia as Kowark et reported ,by combining remifentanil with desflurane.
Some concerns exist regarding the safety of neck insufflations by carbon dioxide since then severe hypercapnia, acidosis, massive subcutaneous emphysema and tachycardia was observed [23,24]. Bellantone et al reported that carbon dioxide neck insufflations is safe ≤10 mmHg but use of insufflations pressures higher than >15 mmHg should be avoided to prevent metabolic and hemodynamic complications [24]. Rubino et al [23] reported that carbon dioxide neck insufflation up to 10 mmHg does not alter intracranial pressure and is recommended for clinical application in endoscopic neck surgery. The important issues during neck insufflation are insufflation pressure and the rate of insufflation. The head and neck region is dense in terms of the vessel and nerve packs. Carbon dioxide neck insufflations may cause negative haemodynamic effects by compressing these packs. We must take care (atropine, ephedrine, adrenaline, large vessel, close communication with surgeon for urgent desufflation etc) during insufflation phase of surgery.
On the other hand, PTH itself causes alterations in vasodilatory properties of endothelium by hypercalcemia which leads to short QT intervals, prolongation of PR and QRS intervals and myocardial depression [25]. Therefore, we should follow ECG changes and hemodynamic parameteres more closely during anesthesia induction, hydrodissection and insufflation.
We does not prefer N2O in laparoscopic surgeries in our clinical practice. In addition, N2O increases postoperative nausea and vomiting [9,21] which is a drug side effect that we do not want to encounter in patients with TOEPVA, not to met with any infection postoperatively.
Conclusion: This is the first study which describe the anesthetic management for TOEPVA in the literature. After induction of anaesthesia with propofol, remifentanil and rocuronium; anesthesia management by desflurane co-administered with continous infusion of remifentanil, provide feasible and safe anaesthesia for TOEPVA. However, especially during hydrodissection and insufflation, a close cooperation between surgeon and anaesthetist have a great value to improve patient management.Further studies are needed on anesthesia management for TOEPVA in clinical practice.
Conflict of interest/Funding disclosure statements
Fulya YILMAZ and Koray BAS have no conflicts of interest or financial ties to disclose.