Tube-in-tube emergency airway management after a bitten endotracheal tube caused by repetitive transcranial electrical stimulation during spinal cord surgery.

WE report a case of bite damage to a wire-reinforced endotracheal tube caused by transcranial electrical stimulation (TES). A 23-yr-old female patient (American Society of Anesthesiologists grade I) with mild motor deficits in the lower extremities was admitted for the extirpation of an intramedullary cervical spinal cord tumor (C3–C7). Intraoperative neurophysiological monitoring by using motor-evoked potentials (MEPs) elicited by TES and somatosensory-evoked potentials was performed to assess the functional integrity of the spinal cord. After induction of general anesthesia by using bolus administration of propofol, remifentanil, and muscle relaxation (0.6 mg/kg rocuronium), a 7.5-mm ID armoured endotracheal tube with cuff (Rüschflex; Teleflex, Kernen, Germany) was introduced, cuffed, and fixed with adhesive tape. A gauze bite block was placed in the recommended manner to prevent bite injuries because tongue bites, lip lacerations, and even a unique case of mandibular fracture were reported during TES in patients without bite block. Anesthesia was maintained by continuous infusion of propofol (100 g · kg 1 · min ) and remifentanil (0.5 g · kg 1 · min ). The neuromuscular blockade was omitted after induction of general anesthesia to avoid interference with MEP monitoring. Neurosurgical access was intended from the posterior; therefore, the patient was turned to a prone position, and TES for MEP monitoring was initiated. Scalp electrodes at positions C3 and C4 were used for TES according to the International 10–20 electroencephalography electrode system. Short trains of 5–7 electrical pulses (frequency 250 Hz, duration of each stimulus 0.5 ms, intensity 80 to 250 V) were applied via corkscrew electrodes originating from a Nicolet Endeavor (Viasys Healthcare, Madison, WI) constant current stimulator to monitor MEPs from limb muscles. Single stimuli of TES were used to record epidural MEPs from an intraoperatively placed epidural catheter electrode. At critical stages of the surgical procedure, short trains of stimuli were used at a rate of 1.1 Hz to continuously assess the functional integrity of motor tracts. During the entire surgical procedure, a total of 4,200 trains of stimuli were applied. Approximately 6 h after incision, the ventilator alarmed leakage. At this point, oxygenation and ventilation could only be performed by high-flow hand ventilation with 100% oxygen. Direct inspection of the endotracheal tube with the patient remaining in prone position revealed a bitten hole near the incisors (fig. 1), although the gauze bite block was still correctly in place. In this emergency situation, a thinner, 5 mm endotracheal tube (Microcuff; Kimberly-Clark, Neenah, WI) (table 1) was inserted into the injured endotracheal tube