Acromegaly
Acromegaly is a syndrome caused by oversecretion of growth hormone after long bone epiphyseal fusion. The pathology is usually an anterior pituitary tumour, but it can also arise from other hormonally active tumours. Acromegaly affects males and females equally. It has an incidence of 3–4 per million per year, and a prevalence of 50–70 cases per million population. It has an insidious onset and usually presents in middle age with the classical physical appearance of bony overgrowth of the hands, feet, and facial bones, and soft tissue enlargement of the upper airway.
1 Discuss the airway difficulties and comorbidities that present in a patient with acromegaly
2 Outline a plan for the induction of anaesthesia in an acromegalic patient for elective surgery.
1C01; 2A01
A 45-year-old male with acromegaly presents for transphenoidal removal of a pituitary tumour. Airway assessment reveals normal dentition, a large tongue, Mallampati class 3, an interincisor gap of 3 cm, mandibular protrusion class A, thyromental distance of 7 cm, and good atlanto-occipital movements.
◆ Coarsening of features
◆ Large hands and feet
◆ Prominent supraorbital ridges
◆ Wide nose
◆ Nerve compression syndromes
◆ Kyphoscoliosis
◆ Skin thickening, increased sweating/sebum production
◆ Arthropathy
◆ Myopathy.
◆ Macroglossia
◆ Prognathism with malocclusion
◆ Hypertrophy of pharyngeal and laryngeal soft tissue—epiglottis, aryepiglottic folds
◆ Fixation and thickening of the vocal cords
◆ Recurrent laryngeal nerve palsy
◆ Decreased width of the cricoid arch
◆ Glottic/subglottic stenosis.
◆ Hypertension—40%
◆ LV hypertrophy
◆ Ischaemic heart disease
◆ Congestive cardiac failure
◆ Cardiomegaly
◆ Conduction defects and arrhythmias.
◆ Diabetes—25%
◆ Obstructive sleep apnoea—70%
◆ Pulmonary function tests—extrathoracic obstruction
◆ Visceromegaly
◆ Mass effects from tumour—visual field defect (optic chiasm compression), headache.
The nature of airway difficulty can be unpredictable and difficult to accurately identify. First, there may be a problem in maintaining a patent airway with a face mask, due to the large tongue and general upper airway soft tissue hypertrophy, when muscle tone is lost under general anaesthesia. This is particularly relevant in those with a history of obstructive sleep apnoea. In addition, the application of a face mask may be awkward, due to a large head and jaw. Second, direct laryngoscopy and tracheal intubation may also be difficult. SGAs may not be helpful, due to soft tissue hypertrophy.
The following statistics have been previously reported:
◆ 39% of acromegalics had some degree of airway difficulty (Seidman)
◆ 26% (Schmitt) to 33% (Hakala) had a Cormack and Lehane grade 3 or 4 view at laryngoscopy
◆ 10% were a difficult intubation (Schmitt, Nemergut/Zuo)
◆ Asleep fibreoptic intubation may fail (Hakala).
Routine airway assessment may also give an inaccurate prediction. Twenty per cent of acromegalics with a Mallampati class 1 or 2 may be difficult to intubate.
Patients with acromegaly require a very careful and thorough airway assessment. If there is any concern regarding the ability to maintain a patent airway, then a technique whereby the airway is secured awake is the safest option. In practice, this means an AFOI.
An airway strategy should be formulated with a plan A, and a backup plan should that fail. This must be communicated to the anaesthetic assistant. All equipment should be checked with regard to its availability, cleanliness, and functionality.
A reinforced (armoured) ETT is best to avoid the risk of kinking. (A preformed south-facing ETT may not be long enough in an acromegalic.) The ETT should be taped to the opposite side from the nostril used for surgical access. A throat pack should be inserted, and its use documented, as per local protocol. Documentation of the Cormack and Lehane grade under direct laryngoscopy post-AFOI is useful for any future intubations.
This patient underwent an uneventful AFOI, using a spray-as-you-go technique, with remifentanil 0.1 micrograms/kg/min sedation.
Much is written and talked about with regard to difficult intubation. Often, less attention is paid to extubation. This is potentially a very risky time. This patient will have nasal packs in and a throat pack which should be removed and documented as done. The oropharynx should be carefully suctioned under direct vision, including the posterior nasopharynx. There will probably be blood present which has the risk of causing laryngeal obstruction post-extubation—commonly referred to as a ‘coroner’s clot’.
Any residual neuromuscular block must be reversed, and discontinue general anaesthesia. Adequate long-acting analgesia should have been given. A smooth emergence is the aim to minimize the chance of increased venous pressure from coughing, causing further bleeding. Continuing the remifentanil infusion is very helpful in achieving this. (Remifentanil is commonly used intraoperatively to obtund the hypertensive response to periods of intense surgical stimulation. Its context-insensitive half-life ensures a rapid offset, regardless of the rate and duration of infusion.) The patient should obey commands and have regular spontaneous respiration before the ETT is removed. The patient should be extubated in the sitting position to optimize airway and respiratory function. There will be obligate mouth breathing, due to the nasal packs.
After every extubation, there should be a clear plan for reintubation, should that be necessary, with appropriate equipment and staff available.
Supplemental oxygen, ideally via a capnography mask, is given in the immediate post-operative period. A more prolonged period of observation will be required for those with a history of obstructive sleep apnoea.
Summary
Due to the potential problems of airway maintenance and intubation, AFOI has increasingly become the technique of choice. As such, there is little recent evidence regarding the optimal method of securing the airway under general anaesthesia, and nothing published regarding the use of videolaryngoscopes in these patients. A Plan A and an escape plan for extubation should be formulated as a routine in patients with advanced airway management at induction.
Hakala P, Randell T, and Valli H (1998). Laryngoscopy and fibreoptic intubation in acromegalic patients. British Journal of Anaesthesia, 80, 345–7.
Menon R, Murphy PG, and Lindley AM (2011). Anaesthesia and pituitary disease. Continuing Education in Anaesthesia, Critical Care & Pain, 11, 133–7.
Nemergut EC,Dumont AS,Barry UT, and Laws ER (2005). Perioperative management of patients undergoing transsphenoidal pituitary surgery. Anesthesia & Analgesia, 101, 1170–81.
Nemergut EC and Zuo Z (2006). Airway management in patients with pituitary disease. A review of 746 patients. Journal of Neurosurgery and Anesthesiology, 18, 73–7.
Reddy R,Hope S, and Wass J (2010). Acromegaly. BMJ, 341, 400–1.
Schmitt H, Buchfelder M, Radespiel-Tröger M, and Fahlbusch R (2000). Difficult intubation in acromegalic patients: incidence and predictability. Anesthesiology, 93, 110–14.
Seidman PA,Kofke WA,Policare R, and Young M (2000). Anaesthetic complications of acromegaly. British Journal of Anaesthesia, 84, 179–82.
Smith M and Hirsch NP (2000). Pituitary disease and anaesthesia. British Journal of Anaesthesia, 85, 3–14.