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Wire-reinforced endotracheal tube penetrated by the Harmonic Scalpel[R].

The Harmonic Scalpel[R] (HS) is based on an ultrasonic technique and widely used in otolaryngologic procedures. Dr Coulson observed that the HS causes marks on polyvinyl chloride (PVC) endotracheal tubes (ETT) but that it does not cause ignition (1). Clinically, PVC ETT damage has been reported in two patients who received head and neck surgery using the HS and ignition was not mentioned (2,3). However, depending on the working time, Emam et al found the jaw temperature of the HS can reach 297[degrees]C (4). If the temperature is kept too high, charring is possible. Since there was no report regarding wire-reinforced PVC ETT, we would like to alert users to a perforated and charred wire-reinforced PVC ETT (Safety-Flex[TM], Mallinckrodt Medical, Athlone, Ireland) during tonsillectomy with HS (Utracision Harmonic Scalpel-Generator 300, Ethicon Endo-Surgery, Cincinnati, OH, USA).

A tonsillectomy and radiofrequency over the tongue base were scheduled for a 26-year-old male with a body mass index of 34, who was admitted for uvulopalatopharyngoplasty. General anaesthesia was induced with 150 mg propofol, 50 mg rocuronium and 5% sevoflurane. A 7.5 mm ID oral wired reinforced PVC ETT with cuff was used. Anaesthesia was maintained with 5% sevoflurane in oxygen.

When the right tonsillectomy was almost completed, white smoke accompanied by an unpleasant odour was noticed when the HS probe (DH145, Ethicon Endo-Surgery, Cincinnati, OH, USA) was applied to the right side of the tonsil to dissect its lower pole. Meanwhile, the ventilator suddenly released a low airway pressure alarm and stopped functioning.

Damage to the ETT was suspected. The patient was re-intubated with a new wire-reinforced ETT. The ventilation then returned to normal. The operation was resumed and completed without any other unusual incident. The first tube was found to have a hole about 1 mm in diameter 6 cm above the cuff (Figure 1A), with char around the hole (Figure 1B) and the coil deformed.

[FIGURE 1 OMITTED]

Unlike the uni-pole electrocautery and laser devices, the ETT usually needs special protection to prevent ignition (5,6). HS is usually employed with a low energy and thus resulting in a low temperature but it is not completely free from thermal injury. The temperature of the HS is in direct proportion to the activation time and power setting. At level 4, the peak temperature at the jaw of the probe is around 100[degrees]C in short bursts, but can reach 200[degrees]C when the activation time exceeds 10 seconds. It can reach 297[degrees]C within 13.1 seconds when continuously activated at level 5 (4). In addition, because the vibration works on the hard and solid coil at very high-frequency, using the HS with the wire-reinforced tube may result in higher jaw temperature. It is thus essential to keep the power level low and the exposure time short (4).

In this case a wire-reinforced ETT with PVC was used. The melting point of PVC is 80[degrees]C. Its flash ignition temperature is 260[degrees]C. The temperature of jaw of the HS probe can reach the PVC's melting point when the jaw approaches the ETT within 1 cm with a power setting at level 4 for just five seconds of exposure, or even at the level 3 when the continuous activation lasts longer than 10 seconds. Few former reports have referred to charring. When the HS probe reaches 297[degrees]C (4), it exceeds the flash ignition point of PVC (260[degrees]C). Thus, charring may be rare but is possible, especially when the jaw of the HS probe is attached to the wired reinforced ETT with PVC.

The working principle of the HS is high-frequency vibration, which generates the highest temperature at the jaw of the probe. If the probe jaw is out of sight, this may result in severe mechanical thermal injury. In this case, where the patient's body mass index was high (34), the inflamed tonsil was quite large and the patient's tongue was relatively thick, hence the space available for operation was limited. It is possible that part of the probe jaw may have contacted the ETT and thus likely caused tube damage and charring. Therefore, HS should be used such that its jaw can be clearly seen.

In conclusion, though the temperature of the HS probe is lower than that of laser and electrocautery apparatus, damaging and/or charring reinforced PVC ETT by the HS is still possible. The HS should be used in such a way that the probe can be clearly seen, with lower power levels and shorter durations

References

(1.) Coulson AS, Bakhshay SA. Harmonic scalpel prevents tracheotomy fires. Chest 1998; 114:349-350.

(2.) Balakrishnan M, Kuriakose R. Endotracheal tube damage during head and neck surgeries as a result of Harmonic Scalpel use. Anesthesiology 2005; 102:870-871.

(3.) Hayakawa M, Morimoto Y, Kemmotsu O. [Tracheal tube damage by Harmonic Scalpel during tonsillectomy]. Masui 2000; 49:1261-1262.

(4.) Emam TA, Cuschieri A. How safe is high-power ultrasonic dissection?

Ann Surg 2003; 237:186-191.

(5.) Walker P, Temperley A, Thelfo S, Hazelgrove A. Avoidance of laser ignition of endotracheal tubes by wrapping in aluminium foil tape. Anaesth Intensive Care 2004; 32:108-112.

(6.) Kwan A. The use of Storz bronchoscope in prevention of airway fire. Reply. Anaesth Intensive Care 2004; 32:720.

J. Lee

C.-C. Tseng

W.-H. Huang

P.-C. Che

Y.-S. Tsai

H.-C. Shih

C.-Yi

Taiwan, Republic of China
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Title Annotation:CORRESPONDENCE
Author:Lee, J.; Tseng, C.-C.; Huang, W.-H.; Che, P.-C.; Tsai, Y.-S.; Shih, H.-C.; C.-Yi
Publication:Anaesthesia and Intensive Care
Article Type:Letter to the editor
Date:Mar 1, 2010
Words:907
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