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Ovid: Oxford Handbook of Acute Medicine

Editors: Ramrakha, Punit S.; Moore, Kevin P. Title: Oxford Handbook of Acute Medicine, 2nd Edition Copyright ©1997,2004 Oxford University Press (Copyright 1997, 2004 by Punit S Ramrakha and Kevin P Moore) > Table of Contents > Chapter 9 – Endocrine emergencies > Phaeochromocytomas: assessment Phaeochromocytomas: assessment

  • Phaeochromocytomas are catecholamine-producing tumours usually involving one or more adrenal glands. ~0% are bilateral, ~10% are extra-adrenal [usually around the sympathetic chain (paragangliomas)] and ~10% are malignant. They usually secrete AD or NA. A small proportion secrete DA, when hypotension may occur.
  • Most are diagnosed during routine screening of hypertensive patients (they are found in only 0.1% of hypertensives). Pure AD-producing tumours may mimic septic shock due to AD-induced peripheral vasodilatation (β2-receptors).

Presentation

  • Classically a triad of episodic headaches, sweating, and tachycardia
  • Hypertension (mild to severe sustained ± uncontrolled paroxysmal, hypertensive episodes) and orthostatic hypotension (low plasma volume). 50% have sustained ↑BP and 50% have paroxysmal ↑BP
  • Anxiety attacks, tremor, palpitations, cold extremities, and pallor
  • Cardiac dysrhythmias (incl. AF and VF) and dilated cardiomyopathy
  • Hypertensive crises may be precipitated by β-blockers, tricyclic anti-depressants, metoclopramide, and naloxone
  • Unexplained lactic acidosis
  • Triggers for hypertensive crises include surgery, opiates and contrast media.

Investigations There are no tests which will diagnose a phaeochromocytoma acutely. Investigations are listed in the table opposite.

  • Hypertensive patients with ↑glc and ↓K+ may have a phaeochromocytoma, but these are both non-specific features.
  • Urinary VMA level (a catecholamine metabolite) is useful if markedly elevated (5–10× upper limit of normal). Mild elevations are frequent (15%) in patients with essential hypertension, as VMA can be derived from dietary sources, including vanilla essence giving a false +ve test result. Urinary catecholamines (AD, NA, and DA) or metanephrines are more specific. Urine collections must be completed before pentolinium or clonidine tests as withdrawal of these compounds can give a false +ve result.
  • Plasma catecholamines should be collected from an in-dwelling cannula placed over 30 minutes previously in a supine patient. Samples need to be taken directly to the lab (on ice) for centrifugation.
  • Pentolinium suppression test. Take two baseline samples as above, then give 2.5mg pentolinium iv, and take blood again at 10 and 30 minutes. Plasma catecholamines decrease in normal subjects following ganglion blockade with pentolinium. If the response is borderline and no hypotension occurs, then repeat with 5mg pentolinium.
  • Clonidine suppression test. An alternative to the pentolinium suppression test employs clonidine. Following two baseline samples, give 0.3mg clonidine orally, and take blood hourly for 3 hours. Again if raised catecholamines are due to anxiety, they will suppress into the normal range with clonidine. Raised catecholamines from phaeochromocytoma will not be affected by clonidine.
  • P.599

  • MRI or CT of the abdomen are useful to localize the tumour. Radiocontrast can lead to catecholamine release.
  • MIBG scan. MIBG (131I-metaiodobenzylguanidine) is taken up selectively by adrenal tissue. Useful to localize tumour or secondaries.
  • Selective venous sampling: to localize extra-adrenal tumours.

Investigations for suspected phaeochromocytoma

  • U&Es (↓K+, ↑urea)
  • Glucose (↑)
  • Urinary VMA
  • Urinary catecholamines (AD, NA, and DA), metanephrines
  • Plasma catecholamines (AD, NA, and DA)
  • Pentolinium suppression test
  • Clonidine suppression test
  • MRI or CT scan of adrenals
  • MIBG scan for localization

Other causes of sympathetic overactivity

  • Abrupt withdrawal of clonidine or β-blockers
  • Autonomic dysfunction e.g. Guillain–Barré syndrome or post spinal cord injury
  • Stress response to surgery, pain, or panic
  • Sympathomimetic drugs
    • Phenylpropanolamine (decongestant)
    • Cocaine
    • MAOI plus tyramine-containing foods (cheese, beer, wine, avocado, bananas, smoked or aged fish/meat)

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