In this case, emergency intubation was performed because upper airway obstruction strongly suspected due to expiratory stridor and rapidly worsen dyspnea. His neck was bilaterally swelling and CT showed the bilateral parotid glands swelling and the edema of the posterior pharyngeal wall without hematoma around surgical site. Blood test indicated serum amylase was abnormally elevated. Thus, we diagnosed upper airway obstruction due to the anesthesia mumps. Furthermore, he developed an allergic reaction, which might have caused or intensified the edematous changes in the pharyngeal wall. This might be one of the etiologies that caused upper airway obstruction.
Anesthesia mumps is considered to be an extremely rare complication. According to reports in the literature, its occurrence is highly variable (0.2–17%) [3,4,5], and the exact incidence remains unknown. Although patients can develop postoperative salivary gland swelling, it is typically mild, with few subjective symptoms. Therefore, many cases resolve spontaneously without being noticed. Thus, we believe that the discrepancies in the incidence rate are largely due to variable amount of attention that is paid to this condition.
The cause and detailed pathophysiology of anesthesia mumps remains unknown, but salivary duct occlusion, sialorrhea, venous congestion and venostasis, involvement of the autonomic nerves, and side effects of medications have been suggested [5, 6].
Causes of salivary gland obstruction include (1) physical compression by lateral position, positions that rotate and flex the neck, compression by endotracheal tubes, mucosal lesions and edema; (2) pneumoparotitis induced by the penetration of air as a result of retrograde flow into the salivary duct due to positive pressure in the oral cavity by mask ventilation, pharyngeal reflex, and cough reflex; and (3) dehydration, administration of atropine, and sympathetic nervous system activation due to invasiveness of surgery causing increased salivary viscosity, which may in turn itself cause an occlusion.
Salivation is mediated by the autonomic nerves, and the main secretory innervation is parasympathetic. Intratracheal manipulation stimulates parasympathetic nerves that mediate the pharyngeal reflex, which promotes salivation and leads to vasodilation and hyperemia in the salivary gland [2]. Stimulation of the sympathetic nerves also evokes salivation, but it is relatively short-lasting, the saliva is usually thick and mucinous, and vasoconstriction occurs [7]. Actually, noradrenaline infusion increases salivary alpha-amylase, a digestive enzyme secreted from the salivary glands that has been proposed as a sensitive surrogate maker for activity stress [8].
In the present case, we observed bilateral swelling of the parotid and submandibular glands. Therefore, we considered it unlikely that there was only a mechanical regional occlusion related to patient positioning and pneumoparotitis. We believe that variety of causes led to development of anesthesia mumps. One of them is a venous congestion due to surgical procedure or stimuli of CEA, and the others are excess secretion of saliva due to reflex salivation, the pharyngeal reflex or continuous administration of noradrenaline. However, the exact causes remain unclear.
Several reports state that most cases of anesthesia mumps resolve spontaneously with follow-up observation alone, it has been considered that rehydration therapy and anti-inflammatory drugs if needed are sufficient to treat it [1, 2]. However, there may be cases, such as the present case, in which patients suffer from severe complications, including upper airway obstruction [9, 10]. In our patient, the combined approach of a video laryngoscope and a gum elastic bougie tube introducer resulted in a successful re-intubation without the need for tracheostomy. Emergency tracheostomy might be often chosen because of difficult mask ventilation and the possibility of intubation difficulty for postoperative dyspnea and acute airway obstruction [10]. However, in cases involving massive edema and swelling of the neck, it is difficult to identify the location of the tracheostomy. Video laryngoscopes could well become the standard procedure for these types of patients who need emergency tracheal intubation. Hence, additional measures to treat these conditions are required, and conscientious follow-up observation is necessary.