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zona glomerulosa of the adrenal cortex, resulting in excessive production of aldosterone and leading to
sodium retention and renin suppression. The symptoms and clinical signs include muscle weakness,
polyuria, hypertension, hypokalaemia, alkalosis, retinopathy, intermittent paralysis, cardiac arrhythmias,
paraesthesiae, tetany-like symptoms, and psychiatric disturbances. It is slightly more frequent in women
and usually occurs in patients 30 to 50 years of age. It is found in one per cent of those who present with
mild hypertension and hypokalaemia. It can present with hypokalaemic paralysis, especially in the
Chinese. If the hypertension has been treated with thiazide, this will obviously worsen the hypokalaemia.
In over 80 per cent of cases, this syndrome is associated with an aldosterone producing adenoma or
carcinoma.
Investigation
Repeated plasma potassium taken with care to avoid haemolysis. If confirmed, it is then appropriate to
measure plasma aldosterone and renin activity. In Conn’s syndrome, aldosterone levels would be elevated
and the renin suppressed. An abdominal CT-scan or MRI may be helpful in visualising an adenoma.
Treatment
If an adenoma is demonstrated, the definitive treatment is surgical removal. If bilateral hyperplasia is the
problem, the best treatment is with the aldosterone antagonist spironolactone. If glucocorticoid remedial
hypertension is suspected, 2-3 weeks of dexamethasone may be given.
Operational implications
9 Conn’s syndrome: primary hyperaldosteronism. Named after Jerome W. Conn, American internist (1907-1981)
ICAO Preliminary Unedited Version — March 2010 III-4-13
Individuals with active Conn’s syndrome with hypokalaemia and hypertension are unfit for all aviation
duties.
Aeromedical considerations
If an adenoma is diagnosed and removed, the applicant is cured and medical certification should not be a
problem with regular endocrinology follow-up. If the patient is on long term spironolactone, individual
assessment is appropriate with full endocrinology reports to aid the decision on medical certification.
ADRENAL MEDULLA
Phaeochromocytoma
Aetiology and Pathogenesis
The phaeochromocytoma is a tumour secreting catecholamines. It is a rare tumour, the figure often quoted
is 0.1 per cent of cases of hypertension. Recent data suggests the prevalence may be higher. The tumours
are usually found in the adrenal medulla, ten per cent being bilateral. However, ten per cent arise in extraadrenal
chromaffin tissue, usually in the sympathetic chain in the abdomen, but can be found anywhere in
the sympatho-adrenal system from the neck to the urinary bladder. In multiple endocrine neoplasia
syndrome, it is associated with medullary carcinoma of the thyroid and hyperparathyriodism. These
syndromes are inherited as autosomal dominance; they are rare to aviation medicine practice.
Symptoms and Signs
a) paroxysmal hypertension
b) postural drop (volume depletion) attacks with pallor
c) flushing
d) palpitations, sweating, headache,
e) angor animi
f) abdominal pain, constipation
g) weight loss, glucose intolerance
Investigation
Diagnosis is made by measurement of plasma adrenaline/noradrenaline or their metabolites vanillylmandelic
acid (VMA), metanephrins and nor-metanephrins. The excretion may be paroxysmal and thus
repeated sampling is mandatory.
Tumour imaging can be by ultrasound or CT-scanning, but scanning by MRI is superior as the T2-
weighted image is usually intense. Radioisotope scanning with 131I - MIBG (meta-iodbenzyl guanidine)
is helpful in the demonstration of an ectopic site. This isotope is preferentially taken up by adrenergic
cells.
Treatment
Surgery is the treatment of choice and is curative in some 75 per cent of cases. Before surgery, the patient
must be fully α- and β-blocked. Once the diagnosis is made, pharmacological treatment should be started.
The drug of choice is the α-adrenergic blocking agent phenoxybenzamine (10-20 mg twice daily) or
doxazosin (1-2 mg twice daily), followed a few days later by a β-blocker, e.g. propranolol (10 mg twice
daily). Approximately two weeks should be allowed to replace volume before surgery. When surgical
ICAO Preliminary Unedited Version — March 2010 III-4-14
removal is not feasible or has been incomplete, continued pharmacological treatment can be quite
successful.
Operational implications
Following successful surgery with complete removal of the tumour and no significant end organ damage,
medical certification should be possible after a six-month period of observation.
It is important to consider the possibility of recurrent tumour or malignant activity should hypertension
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Manual of Civil Aviation Medicine 1(128)
