- Phaeochromocytoma is a catecholamine-secreting neuroendocrine tumour.
- Characteristic features include haemodynamic instability and features of heart failure.
- It is classically associated with thyroid carcinoma
- Diagnostic tests include serum and urinary catecholamine levels, a clonidine suppression tests, MRI and octreotide scintigraphy.
- Management consists of sympatholytic drugs, of which the most important is phenoxybenzamine.
- It is important to establish α-blockade before using β-blockers.
For some reason, this rare tumour has attracted the attention of CICM examiners, and has featured in more fellowship exam questions than its community prevalence would suggest.
Past paper SAQs which involved phaeochromocytoma included the following:
- Question 22 from the second paper of 2010
- Question 14.1 from the first paper of 2009
- Question 15.2 from the first paper of 2008
Clinical manifestations of phaeochromocytoma
- Paroxysmal or sustained hypertension
- Palpitations and tachycardia
- Chest pain and myocardial infarction
- Symptoms and signs of heart failure
- Acute pulmonary oedema
A characteristic feature of this disease is that the symptoms occur in paroxysms, and may resolve completely between episodes. The hemodynamic pattern of these episodes resembles the effect of high dose noradrenaline infusion, with α-adrenergic effects dominating over β-effects.
These people may present complaining of death.
Associations with phaeochromocytoma
There is a well-known association between thyroid carcinoma and phaeochromocytoma - investigators in 1961 concluded that "the incidence of carcinoma of the thyroid gland is increased far beyond expectation based on chance concurrence".
Investigations for phaeochromocytoma
Investigations for phaeochromocytoma should include the following:
- Tests for catecholamines and their metabolites
- Urinary catecholamines
- Plasma catecholamines
- Urinary fractionated metanephrines
- Plasma free metanephrines (these appear to be the best single investigation)
- Urinary vanillylmandelic acid
- Clonidine suppression test
- In patients with phaeochromocytoma, serum catecholamine levels will not decrease in response to clonidine.
- Imaging: MRI and/or PET scan
- Specifically, octreotide scintigraphy
There are other, non-phaeochromocytoma reasons for a raised plasma catecholamine level. This article discusses catecholamines in exhausting detail, and dwells extensively on their various elimination mechanisms. On the basis of this, one can create a table with the differential causes of raised plasma catecholamine levels.
Autonomic nervous system
Management of phaeochromocytoma in the ICU
The management of phaeochromocytoma is discussed in an excellent article from the Royal Adelaide hospital. The key is to block the α-adrenoceptors first. Phenoxybenzamine is an exciting exotic substance used exclusively for this purpose, as it is a non-competitive α-antagonist. It binds irreversibly to α-receptors, inactivating them, and no concentration of catecholamines will ever displace it. This is good, because competitive inhibition of α-receptors in this context will face strong opposition from the thousand-times-increased concentration of serum catecholamines.
The Adelaide paper does meantion that their practice has been to use atenolol before giving phenoxybenzamine, so as to ablate the reflexive tachycardia which will result from its use. This is probably because the population reported on in the paper were stable pre-operative outpatients. In the context of an acute crisis, one is obliged to control the vasoconstriction first, using something like phentolamine or sodium nitroprusside.
Overall, one's management should be guided by some sort of interational consensus guidelines, which take the following shape:
- Control of hypertension
- Rapidly acting α-1 antagonist: phentolamine
- Slowly acting non-competitive α-1 antagonist: phenoxybenzamine
- β-antagonist (after α-antagonist)
- Maintenance of circulating volume in the face of vasodilation:
- IV fluid replacement
- Control of AF
- Verapimil, diltiazem, or amiodarone
- Assessment of myocardial damage
- CK and troponin
- Radionuclide imaging - the test of choice currently is 123I-labeled meta-iodobenzylguanide scintigraphy.
Cardiovascular complications of phaeochromocytoma
The typical TTE finding in phaeochromocytoma is catecholamine-induced cardiomyopathy, but a Takotsubo pattern can also emerge. Such things are generally known from case reports, so it is difficult to broadly generalise.