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EQUINE VETERINARY EDUCATION / AE / MAY 2015
Case Report
Broken nasotracheal tube aspiration in a horse during anaesthetic recovery
J. Potter*, K. Allen†, P. Macfarlane and D. Holopherne-Doran Departments of Anaesthesia; and †Equine Sports Medicine, Langford Veterinary Services, University of Bristol, UK. *Corresponding author email:
joeipotter82@yahoo.com.au
Keywords: horse; endotracheal tube; nasotracheal intubation; aspiration; complications; recovery; anaesthesia
Summary A horse was presented for soft palate thermocautery and surgical advancement of the larynx under general anaesthesia, following a history of respiratory noise and poor athletic performance. Physical examination prior to surgery was unremarkable. The horse was anaesthetised and a 20mm cuffed endotracheal tube (ETT) used to intubate the trachea via the right nostril. The cuff was deflated at the end of the procedure and the tube secured in place around the head of the horse for the recovery. The horse was assisted to standing and during this process the end of the nasotracheal tube broke and was observed hanging from the head collar. The remainder of the tube was aspirated into the trachea of the horse. The remaining length of endotracheal tube was removed using a modified endoscopic technique. The horse recovered with no further problems. An unusual complication of a nasotracheal tube left in situ for recovery in a horse is reported and possible reasons for this complication are discussed.
Introduction
Airway obstruction is one of the various complications reported during anaesthetic recovery in horses (Southwood and Gaynor 2003; Wagner 2008). Many factors can lead to post operative upper airway obstruction; accumulation of secretions, surgically-induced haemorrhage and swelling (Taylor and Clarke 2007; Wagner 2008), recumbency-related nasal mucosal oedema especially with a prolonged duration of recumbence (Thomas et al. 1987; Abrahamsen et al. 1990; Lukasik et al. 1997; Southwood et al. 2003), perioperative trauma to the larynx (Holland et al. 1986; Abrahamsen et al. 1990; Dixon et al. 1993) and dorsal displacement of the soft palate (Southwood and Gaynor 2003;Wagner 2008; Bednarski 2009). The presence of a pre-existing condition such as laryngeal hemiplegia can compound the risk of upper airway obstruction (Southwood et al. 2003). Preventative measures to minimise this risk include elevation of the head to facilitate drainage of secretions (Coumbe 1998; Wagner 2008), nasal phenylephrine to reduce mucosal oedema (Lukasik et al. 1997) and placement of nasal, nasopharyngeal, nasotracheal or orotracheal tubes during recovery (Thomas et al. 1987; Coumbe 1998; Wagner 2008; Bednarski 2009; Bettschart- Wolfensberger 2012). In higher risk cases, pre-emptive tracheostomy may be performed (Dixon 1988; Wagner 2008; Bednarski 2009). Nasotracheal tubes are often used during the recovery process with the aim of maintaining airway patency and appear to reduce the risk of upper airway obstruction (Thomas et al. 1987); however, the risk of the tube itself becoming kinked or occluded cannot be overlooked. In
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addition, there are no multicentre, prospective trials to support their use and the recommendations stated are based on individual experience and retrospective case assessment. In the case reported here, a nasotracheal tube was used intraoperatively to allow surgical access to the soft palate. It was decided to leave the tube in place for recovery in order to reduce the risk of upper respiratory tract obstruction following surgery.
Case presentation
A 6-year-old Thoroughbred gelding (593 kg) was presented with a history of abnormal respiratory noise and poor athletic performance. Surgical advancement of the larynx (tie-forward) and thermocautery of the soft palate were deemed necessary. No abnormalities were detected on physical examination.
Endoscopy of the upper airways revealed a laryngeal function score of 1/5 (Lane 2003). Premedication consisted of intravenous (i.v.) acepromazine (0.03 mg/kg bwt i.v., ACP Injection1 2 mg/ml) followed 30 min later with morphine (0.2 mg/kg bwt i.v., morphine sulphate2 30 mg/ml) and romifidine (0.09 mg/kg bwt i.v., Sedivet3 10 mg/ml). Anaesthesia was induced with ketamine 2.2 mg/kg bwt i.v. (Narketan 10)4 and diazepam 0.05 mg/kg bwt i.v. (Diazepam5 5 mg/ml). A 20mm cuffed silicone endotracheal tube (ETT)6 was introduced into the trachea through the ventro-medial meatus of the right nostril and inflated. Nasotracheal intubation was chosen over orotracheal intubation to offer the surgeon improved access to the mouth. The horse was positioned in dorsal recumbency and
connected to a large animal circle breathing system. Anaesthesia was maintained with isofluorane (Isoflo 100%)7 delivered to effect in 100% oxygen. Appropriate intermittent positive pressure ventilation was initiated immediately and continued throughout the procedure. The depth of anaesthesia was assessed using conventional clinical monitoring, palpebral reflexes and neck muscle tone. On 2 occasions, in response to a rapidly lightening plane of anaesthesia and spontaneous movement, further doses of anaesthetic were required. Injection of 0.5 mg/kg bwt ketamine with 0.05 mg/kg bwt midazolam (Hypnovel8 5 mg/ml) and thiopentone 2 mg/kg were administered i.v. on the respective occasions. Additionally, 0.02 mg/kg bwt of romifidine was administered intraoperatively. Invasive blood pressure, heart and respiratory rates, end-tidal carbon dioxide tension and pulse oximetry measurements were recorded. The total duration of anaesthesia was 90 min. At the end of the procedure, the horse was moved into a
padded recovery box and a further 0.02 mg/kg bwt romifidine was administered i.v. The nasotracheal tube was secured
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