Abstract
A 60 year old euthyroid female with huge goitre since ten years, was posted for near- total thyroidectomy. Sevoflurane was used as a sole anaesthetic agent for induction and intubation. Good intubation condition was achieved by sevoflurane, thus avoiding the use of relaxant.

Introduction

Airway control has always been a challenge to the anaesthesiologist. It is often necessary to strike a balance between providing anaesthesia for securing airway and risk of airway obstruction in a potential difficult ventilation case. Inhalational technique has proved useful in such cases to achieve good relaxation for intubation.

Case Report

A 60 year old euthyroid female patient, weighing 40 kg presented with left sided neck swelling since 10 years. The swelling progressed in size slowly over 10 years to attain current dimension i.e. 10 x12 x 4 cm (Figs. 1 and 2). There was no history suggestive of dyspnoea or dysphagia. Patient was more comfortable in lying down in lateral position as compared to supine. The swelling was multinodular, irregular and with palpable lower border. It moved with deglutition. Airway evaluation revealed only restriction of flexion of neck in view of the swelling. There was no radiological evidence of tracheal compression or deviation (Figs. 3 and 4). Indirect laryngoscopy revealed normal bilateral mobile vocal cords.

Injection glycopyrrolate 0.2 mg was given intramuscularly as pre-medication one hour prior to surgery. Patient was monitored with electrocardiogram, pulse oximeter, and non-invasive blood pressure was attached to the patient. After securing an intravenous line, injection midazolam 0.8 mg and injection fentanyl 80 µg was administered intravenously. The patient was then pre oxygenated for three minutes. Patient was induced with oxygen, nitrous oxide and sevoflurane. Sevoflurane was started initially at one mark, the concentration increased after every third breath to 6%. Eyelash reflex was lost at 80 seconds. The patient’s respiratory efforts were assisted and injection lignocaine 80 mg (preservative free) was given intravenously. At the end of three minutes full jaw relaxation was achieved for laryngoscopy. Intubation was performed using 32 F cuffed flexometallic tubes. Tube placement was confirmed by capnometry. Vecuronium was given to maintain relaxation. The entire procedure was smooth with no major haemodynamic fluctuations. Tube was secured and the throat was packed with wet roller gauze. Air injected to inflate the cuff was noted. Post induction, diclofenac suppository 100 mg was inserted per rectal for post operative pain relief. A near total thyroidectomy was performed. The thyroid specimen weighed 800 gm. The underlying tracheal cartilage appeared normal. No decrease in volume required to inflate the cuff to an airtight seal was noted. Patient was reversed using injection glycopyrrolate 0.4 mg and injection neostigmine 2.5 mg. Post extubation, direct laryngoscopy revealed bilateral mobile cords. Patient was observed overnight in the recovery room.

Fig. 1 : Front view of the goiter.	Fig. 2 : Goitre as seen in the lateral view
Fig. 3 : X-ray neck (anterior - posterior view). Calcific areas are seen in the swelling	Fig. 4 : X-ray neck (lateral view) No tracheal deviation or compression noted.

Discussion

The fear of obstructed airway calls for a pre-planned line of induction for thyroid cases. Especially, in huge goitres, conscious intubation or spontaneous induction technique can be tried to secure the airway. Conscious intubation is subjected to patient co-operation. As the patient was asymptomatic with no evidence of tracheal deviation or compression, we opted to secure airway under anaesthesia. Intravenous agent tend to aggravate the airway obstruction by decreasing muscle tone and once administered their action cannot be reduced or reversed immediately, hence these agents are not preferred in an anticipated difficult airway. Inhalational induction allows titration of depth of anaesthesia and preservation of spontaneous ventilation. Halothane has been used in the past for spontaneous induction. However sevoflurane has a faster induction and awakening compared to other volatile anaesthetic except desflurane.¹ Studies have shown it to have lesser respiratory irritation than halothane, enflurane or isoflurane, making it more acceptable as an induction agent.¹ Sevoflurane unlike halothane is relatively benign to cardiovascular system.¹

However due to the rapid washout of sevoflurane, during laryngoscopy, there could be failure of abolishment of laryngeal reflex at intubation. This can be avoided by ventilating with the inhalational agent for a minute or two beyond loss of eyelash. In this case subjective assessment of full jaw relaxation was taken as guide for adequate plane of intubation. The patient was given injection fentanyl and injection lignocaine (preservative free) which helped in suppressing the laryngeal reflexes.

Tracheomalacia often can be a complication of long standing goitre. Decrease in volume required to inflate the cuff to an airtight seal at end of the procedure should alert the possibility of tracheomalacia.² The tracheal cartilage felt normal in this case and cuff leak test was negative. Post extubation patient was asymptomatic.

Conclusion

The induction with sevoflurane is known to be smoother, faster and more pleasant compared to other inhalational agents. Sevoflurane induction is a good option in the management of a difficult airway.

Acknowledgement

We thank the Dean, Dr N. Kshirsagar and Dr L. Dewoolkar, HOD Anaesthesiology, G.S. Medical College and K.E.M. hospital to have granted permission to publish our work. We would like to thank the artist department of K.E.M.H. for their kind co-operation.

1. Brown B Jr. Sevoflurane: Introduction and Overview. Anesth Analg 1995; 81: S1-3.
2. Farling PA. Thyroid disease. Br J Anaesth 2000; 85: 15-28.