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Case Reports  |   November 2009
Tube-in-tube Emergency Airway Management after a Bitten Endotracheal Tube Caused by Repetitive Transcranial Electrical Stimulation during Spinal Cord Surgery
Author Affiliations & Notes
  • Andreas Duma, M.D.
    *
  • Klaus Novak, M.D.
  • Wolfgang Schramm, M.D.
  • * Resident Anesthesiologist, ‡ Professor, Department of Anesthesiology and General Intensive Care, † Staff Neurosurgeon, Department of Neurosurgery, Medical University of Vienna, Austria.
Article Information
Case Reports / Airway Management / Neurosurgical Anesthesia
Case Reports   |   November 2009
Tube-in-tube Emergency Airway Management after a Bitten Endotracheal Tube Caused by Repetitive Transcranial Electrical Stimulation during Spinal Cord Surgery
Anesthesiology 11 2009, Vol.111, 1155-1157. doi:10.1097/ALN.0b013e3181b8f694
Anesthesiology 11 2009, Vol.111, 1155-1157. doi:10.1097/ALN.0b013e3181b8f694
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.1 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 manner2 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.3 Anesthesia was maintained by continuous infusion of propofol (100 μg · kg−1· min−1) and remifentanil (0.5 μg · kg−1· min−1). 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.4 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.1 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 (with care not to mislead the new endotracheal tube through the perforation5), fixed using adhesive tape, and cuffed (fig. 2) without changing the patient’s position. Pulmonary auscultation was normal. The gauze bite block was replaced by a rubber bite block to prevent further biting of the tube, and mechanical ventilation was continued until the end of the surgical procedure. The critical incidence did not lead to decrease in blood oxygen saturation, which constantly remained above 97%, as measured by pulse oximetry.
Fig. 1. Bitten hole caused by repetitive transcranial electrical stimulation. 
Fig. 1. Bitten hole caused by repetitive transcranial electrical stimulation. 
Fig. 1. Bitten hole caused by repetitive transcranial electrical stimulation. 
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Table 1. A Tube-in-tube Study 
Image not available
Table 1. A Tube-in-tube Study 
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Fig. 2. Bitten reinforced tube (7.5-mm inner diameter) with the thinner tube inside (5 mm inner diamter). 
Fig. 2. Bitten reinforced tube (7.5-mm inner diameter) with the thinner tube inside (5 mm inner diamter). 
Fig. 2. Bitten reinforced tube (7.5-mm inner diameter) with the thinner tube inside (5 mm inner diamter). 
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There were no further respiratory complications; however, because of the increased resistance of the inserted 5-mm tube, a higher peak-pressure was necessary for ventilation until extubation at the end of surgery. Postoperational inspection of the endotracheal tube revealed a 23-mm-long laceration located on the convex side of the endotracheal tube, encircling 70% of the outer circumference (fig. 1 and 2). The endotracheal tube perforation on the convex side had been under the upper incisors during the operation. After extubation in the operating room, it was found that the patient had suffered no injuries that might have occurred during the use of TES. The patient was transferred in a stable condition to the postoperative care unit.
Discussion
Several publications have associated the use of wire-reinforced tubes with airway complications such as perforation,5,6 occlusion,7 obstruction,8,9 or dissection.10 There is only a single report of a bitten and consecutively leaking tube caused by jaw muscle contraction after TES11 and a single report of tube obstruction while the patient was in prone position.12 Both were managed in a different manner from our case.
Santos et al  .12 and MacDonald11 reported emergency reintubation; in both cases, the patient had to be returned to the supine position. We managed this critical event without being forced to change the patient’s position by introducing the thinner tube into the perforated one. We decided to do so, because ventilation could be maintained manually, thereby not justifying the high-risk option of breaking the sterile field by altering the position. With this strategy, the intramedullary spinal cord tumor could safely be removed under continual MEP monitoring.
The usual infusion rate of propofol is 25–100 μg · kg−1· min−1and 0.25–1 μg · kg−1· min−1of remifentanil when combined with propofol for maintenance of anesthesia.13 Therefore, anesthesia should have been deep enough at all times, which minimizes the possibility of the laceration being caused by the patient consciously biting the tube. This serious complication was most likely caused by the sum of repetitive strong bites as a side effect of continuous MEP monitoring, rather than by a single strong bite. The duration of the surgical procedure for the removal of an intramedullary spinal cord tumor reaching from C3 to C7 required extraordinarily frequent TES to test the functional integrity of the motor pathways, which is unusual among other types of spinal surgery.
Because of the short duration of masticatory muscle contractions associated with MEPs, no pressure warning occurred at any time, indicating airway obstruction or leakage. Leakage was noted at the point when the ventilator exceeded its standard limit (more than 25% of min volume); before exceeding the limit, this value was not displayed on the main screen (Primus; Dräger Medical, Vienna, Austria). Particularly strong activation of the temporalis muscle has been reported when TES is applied via  the C3 and C4 electrode positions because direct activation of the muscle or the motor part of the trigeminal nerve is induced by the electrical stimulus.14 This can be avoided by using alternative stimulation sites of scalp electrodes, e.g  ., C1 and C2. However, higher intensities of TES are necessary to reach motor threshold if C1 and C2 are used.15 
Conclusion
This emergency event demonstrates that the previously recommended gauze bite block cannot prevent endotracheal tube perforation for surgical procedures with the use of TES for MEP monitoring. Instead, a reliable device that provides both protection of the patient’s oropharynx (tongue, teeth and lips) and protection of the endotracheal tube should be used.16 Our tube in tube management could sufficiently manage this airway emergency situation in prone position. If TES is effectively accomplished via  electrodes on positions C1 and C2, this method should be preferred over C3/C4 stimulation for MEP monitoring in spinal cord surgery.
References
Deletis V, Sala F: Intraoperative neurophysiological monitoring of the spinal cord during spinal cord and spine surgery: A review focus on the corticospinal tracts. Clin Neurophysiol 2008; 119:248–64Deletis, V Sala, F
Negus B: Gauze bite block. Anaesth Intensive Care 1997; 25:589Negus, B
MacDonald DB: Safety of intraoperative transcranial electrical stimulation motor evoked potential monitoring. J Clin Neurophysiol 2002; 19:416–29MacDonald, DB
Klem GH, Luders HO, Jasper HH, Elger C: The ten-twenty electrode system of the International Federation. The International Federation of Clinical Neurophysiology. Electroencephalogr Clin Neurophysiol Suppl 1999; 52:3–6Klem, GH Luders, HO Jasper, HH Elger, C
Eisenach JH, Barnes RD: Potential disaster in airway management: A misguided airway exchange catheter via  a hole bitten into a univent endotracheal tube. Anesthesiology 2002; 96:1266–8Eisenach, JH Barnes, RD
Harrison P, Bacon DR, Lema MJ: Perforation and partial obstruction of an armored endotracheal tube. J Neurosurg Anesthesiol 1995; 7:121–3Harrison, P Bacon, DR Lema, MJ
Haas RE, Kervin MW, Ramos P, Brown J: Occlusion of a wire-reinforced endotracheal tube in an almost completely edentulous patient. Mil Med 2003; 168:422–3Haas, RE Kervin, MW Ramos, P Brown, J
Peck MJ, Needleman SM: Reinforced endotracheal tube obstruction. Anesth Analg 1994; 79:193Peck, MJ Needleman, SM
Eipe N, Choudhrie A, Pillai AD, Choudhrie R: Neck contracture release and reinforced tracheal tube obstruction. Anesth Analg 2006; 102:1911–2Eipe, N Choudhrie, A Pillai, AD Choudhrie, R
Jeon YS, Kim YS, Joo JD, Kang EG, In JH, Choi JW, Cho SM: Partial airway obstruction caused by dissection of a reinforced endotracheal tube. Eur J Anaesthesiol 2007; 24:983–4Jeon, YS Kim, YS Joo, JD Kang, EG In, JH Choi, JW Cho, SM
Macdonald DB: Intraoperative motor evoked potential monitoring: Overview and update. J Clin Monit Comput 2006; 20:347–77Macdonald, DB
Santos IA, Oliveira CA, Ferreira L: Life-threatening ventilatory obstruction due to a defective tracheal tube during spinal surgery in the prone position. Anesthesiology 2005; 103:214–5Santos, IA Oliveira, CA Ferreira, L
Morgan GE, Mikhail MS, Murray MJ: Clinical Anesthesiology, 4th Edition. Hightstown, McGraw-Hill, 2005Morgan, GE Mikhail, MS Murray, MJ Hightstown McGraw-Hill
Kothbauer KF, Deletis V, Epstein FJ: Motor-evoked potential monitoring for intramedullary spinal cord tumor surgery: Correlation of clinical and neurophysiological data in a series of 100 consecutive procedures. Neurosurg Focus 1998; 4:e1Kothbauer, KF Deletis, V Epstein, FJ
Szelenyi A, Kothbauer KF, Deletis V: Transcranial electric stimulation for intraoperative motor evoked potential monitoring: Stimulation parameters and electrode montages. Clin Neurophysiol 2007; 118:1586–95Szelenyi, A Kothbauer, KF Deletis, V
Shepherd J, Douglas S: Bite blocks and tube obstruction. Anaesthesia 2006; 61:406–7Shepherd, J Douglas, S
Fig. 1. Bitten hole caused by repetitive transcranial electrical stimulation. 
Fig. 1. Bitten hole caused by repetitive transcranial electrical stimulation. 
Fig. 1. Bitten hole caused by repetitive transcranial electrical stimulation. 
×
Fig. 2. Bitten reinforced tube (7.5-mm inner diameter) with the thinner tube inside (5 mm inner diamter). 
Fig. 2. Bitten reinforced tube (7.5-mm inner diameter) with the thinner tube inside (5 mm inner diamter). 
Fig. 2. Bitten reinforced tube (7.5-mm inner diameter) with the thinner tube inside (5 mm inner diamter). 
×
Table 1. A Tube-in-tube Study 
Image not available
Table 1. A Tube-in-tube Study 
×