1.3 Acromegaly + Trans-Sphenoidal Hypophysectomy

Question 1

A 45-year-old male with acromegaly presents for an elective trans-sphenoidal hypophysectomy.
a) What is the cause of acromegaly in this patient? (10%)

Answer 1

Hypersecretion of growth hormone from a pituitary adenoma.

Question 2

b) List the clinical features of acromegaly of relevance to the anaesthetist. (45%)

Answer 2

Airway:
» Large lips, macroglossia, macrognathia, thickening of pharyngeal tissues, laryngeal stenosis. Possibility of difficult airway should be considered.

Respiratory:
» Obstructive sleep apnoea (OSA) with risk of hypoventilation and respiratory failure postoperatively.

Cardiovascular:
» Hypertension, left ventricular hypertrophy, cardiomyopathy with diastolic dysfunction, valvular regurgitation, ECG changes.

> > Increased peripheral soft tissue deposition may make cannulation difficult.

Neurological:**
1&raquo_space; Raised ICP (obstruction of the 3rd ventricle).

2&raquo_space; Spinal cord compression.**
Meticulous care with padding and positioning required.

3&raquo_space; Peripheral neuropathies*
due to impingement by soft tissue or bony overgrowth.

Endocrine:
» Diabetes mellitus.
Blood glucose should be monitored and managed with insulin intraoperatively if necessary.

Gastrointestinal:
» Increased risk of colonic polyps and cancer** –
may necessitate surgery.

Cutaneomusculoskeletal:
» Osteoarthritis, bony overgrowth around joints,
limited movement. Care with positioning and padding.

Renal:
» Renal dysfunction may impact on perioperative drug choices.

Question 3

c) How do the surgical requirements for this procedure influence the conduct of the anaesthesia? (45%)

Answer 3

Surgical requirement + Conduct of anaesthesia

1. Use of operating microscope. **

‘Hypotensive’ anaesthesia,
intra-arterial monitoring,
immobile patient
(muscle relaxant or remifentanil infusion).

Preparation of nasal mucosa*
e.g. Moffat’s solution
or phenylephrine.

2. Periods of intense stimulation
   and periods of minimal stimulation.

Blood pressure may be very labile,
necessitating intra-arterial monitoring.
Remifentanil is ideal for
management of periods of intense stimulation.

3. Supine position with head-up tilt.
   Potential for air embolism.
   Ensure adequate intravenous filling.*
4. Operation on head.

Airway under drapes, armoured tube, anaesthetist distant from airway, meticulous securing of tube, protection of eyes, nerve stimulator on leg, circuit extensions for breathing system and for intravenous fluids.

5. Risk of bleeding from internal carotid or cavernous sinus.*

Intubate (anticipate difficult airway),
throat pack, two group and save samples preoperatively.

6. Rapid emergence*
   need ability to assess neurology as soon as possible postoperatively.

Use of short-acting and rapidly reversible agents.

7. Suprasellar portion of tumour
   may need pushing into surgical field.

Lumbar drain with injection of saline or, less commonly,
controlled ventilation to ensure high-normal PaCO2.

8. Avoid postoperative surges in ICP,**
   especially if CSF leak has occurred.

Smooth emergence, adequate reversal, adequate
antiemetic, airway and CPAP for known OSA.

Question 4

Anatomy / physiology review of pituitary

Answer 4

Adenohypophysis or anterior pituitary:
hypothalamus releases inhibitory or secretory factors, which
travel via the portal system
to the anterior pituitary,

where they control the release of
the anterior pituitary hormones.

Neurohypophysis or posterior pituitary:
neurosecretory cells in the
hypothalamus make
oxytocin and vasopressin,
which travel down axons to
be released from the posterior pituitary.

Question 5

A 54-year-old male with acromegaly presents for a trans-sphenoidal hypophysectomy.
a) What is acromegaly? (2 marks)

Answer 5

Multisystem disease due to pituitary macroadenoma that causes increased release in GH

> > Acromegaly is the condition that results from excessive growth hormone secretion
after the growth plates have fused.

> > In this patient and 90% of cases, it results from hypersecretion from a pituitary adenoma.

> > Occasionally, it may result from an ectopic pituitary adenoma near, but not in, the sella turcica.

> > Rarely, it results from secretion of growth hormone releasing hormone or growth hormone by lung, pancreatic or adrenal tumours.

Question 6

c) What other clinical presentations of a pituitary adenoma may be encountered? (2 marks)

Answer 6

Non-secretory presentation:
» Local pressure effects causing visual disturbance (bitemporal hemianopia), headache.

> > Raised intracranial pressure: cranial nerve palsies, hydrocephalus due to 3rd ventricle outflow blockage.

Hypersecretory presentation:
» Cushing’s disease: hypersecretion of adrenocorticotrophic hormone (ACTH) resulting in fatigue, truncal obesity, striae, moon face, buffalo hump, hypertension, glucose intolerance, hirsuitism, depression, anxiety.

> > Hyperpituitarism:
hypersecretion of any/all anterior pituitary hormones.

Hyposecretory presentation:
» Pituitary apoplexy:
internal haemorrhage of the adenoma, or when
the adenoma outgrows its blood supply, causing tissue necrosis and swelling.

Therefore, there is loss of anterior pituitary hormones.

Symptoms include visual loss, sudden-onset headache, cardiovascular instability.

> > Central diabetes insipidus: a macroadenoma may cause damage to posterior pituitary blood supply, thus (rarely) causing diabetes insipidus with polyuria and polydipsia.

> > Pituitary-related hypothyroidism: generally less severe than hypothyroidism of thyroid origin.

> > Adrenocortical insufficiency: again, not as severe as adrenocortical insufficiency of adrenal origin.