Dr. Saenz is a staff anesthesiologist and Dr. Guruli is chief of Anesthesiology Service, both at G.V. (Sonny) Montgomery VAMC in Jackson, Mississippi. Dr. Saenz and Dr. Guruli also are both assistant professors of anesthesiology at the University of Mississippi Medical Center in Jackson.
Dexmedetomidine was successfully used for a patient with obesity and may reduce the need for opioids in sedation.
The following case report describes the use of dexmedetomidine as the primary sedative for an awake endotracheal intubation, as an adjuvant for general anesthesia, and for postoperative sedation for mechanical ventilation. This case illustrates problems that attracted the attention of federal institutions, specifically the management of difficult airways (with and without anatomic distortion), obesity, and obstructive sleep apnea (OSA). As such, it is of potential interest not only to anesthesiologists, but also other health care providers in the VA, especially those who might practice in intensive care settings.
Dexmedetomidine has useful pharmacologic properties that have potential use in a wide variety of clinical scenarios. Dexmedetomidine is currently indicated for sedation in nonintubated patients before and during surgical and other procedures and in intubated and mechanically ventilated patients during treatment in an intensive care setting.
Large neck masses can produce numerous problems that complicate the anesthetic management in the intraoperative and immediate postoperative arenas. The adjuvant use of dexmedetomidine, an alpha-2 agonist that has useful properties for both the anesthetic and intensive care situations, will be discussed. The problems involved with the management and resection of large neck masses include tracheal deviation, tracheal compression, airway edema, distorted anatomy, difficult mask ventilation, difficult intubation, postoperative recurrent laryngeal nerve dysfunction, and difficult exposure for tracheostomy.
Case Report
A 46-year-old man was referred for removal of a large thyroid mass. His past medical history included hypertension, obesity, and type 2 diabetes mellitus. Clinically, the patient seemed to be at risk for OSA, but he had not received a formal diagnosis. The patient met many of the criteria for screening OSA that are listed for a STOP-Bang Questionnaire.1 He was clinically and serologically euthyroid. Neck ultrasound revealed a very large thyroid mass with cystic and solid lesions throughout. Other than hoarseness, the patient reported no compressive symptoms, such as dysphagia or airway compromise. He was maintained on metoprolol, fosinopril, a thiazide for hypertension, and metformin and insulin for diabetes. A physical examination was remarkable for a Mallampati IV airway classification, a 61-cm neck circumference, 177 cm height, 142 kg weight, and a body mass index of 45. These preoperative assessments were predictive of a high probability of very difficult mask ventilation and intubation after the induction of a general anesthetic, or in any other situation requiring tracheal intubation, such as respiratory failure in the postoperative period.
Preoperative laboratory studies, chest radiograph, and electrocardiogram (ECG) were unremarkable. Computed tomography (CT) imaging of the neck revealed marked enlargement of the thyroid, which had a multinodular, heterogeneous appearance with scattered calcifications. The left lobe of the thyroid measured 13.0 cm craniocaudal by 9.47 cm transverse by 6.8 cm anteroposterior. The right lobe of the thyroid measured 12.0 cm craniocaudal by 7.6 cm transverse by 7.0 cm anteroposterior (Figure 1).
The first concern for this patient was a secure airway, which potentially could have been very difficult to procure with a standard IV induction of anesthesia followed by a direct laryngoscopy. This was further constrained by the surgical requirement that the patient be intubated with an electromyography (EMG) endotracheal tube for monitoring of the recurrent laryngeal nerves, as thyroid surgery carries the risk of injury to these nerves. The type of tube that was used had a larger diameter than that of a standard endotracheal tube (the EMG tube measured 10.2 mm outside diameter vs 9.6 mm outside diameter for a standard tube) but was also far more rigid, precluding nasal intubation and making navigation of the tip around corners and obstructions more difficult. A final laryngoscopy was also needed for confirmation of optimal electrode placement at the vocal cord level (Figure 2).
The anesthetic plan was to secure the airway with an awake oral fiberoptic intubation under sedation and topical local anesthetic to avoid the hypoxemia that would ensue if the patient lost spontaneous respiration. The patient was brought without preoperative sedation to the operating room, standard monitors (eg, ECG, noninvasive blood pressure, pulse oximetry) were applied and IV access was obtained. Blood pressure, heart rate, and oxygen saturation were within normal limits. He was placed on oxygen 2 L/min by nasal cannula and given a 1 μg/kg loading dose of dexmedetomidine over 10 minutes and thereafter maintained on a 0.4 μg/kg/h maintenance infusion during the entire airway intubation sequence. A topical anesthesia of 4% lidocaine spray was applied to the upper airway, and a transtracheal injection was performed with 2 mL of 4% lidocaine. The patient’s anatomy precluded the use of superior laryngeal nerve blocks. During the dexmedetomidine loading, he was given 1 mg midazolam and 100 μg fentanyl IV incrementally. No significant hemodynamic or respiratory changes occurred with this sedation regimen.
