63. Phaeochromocytoma Flashcards
You are asked to anaesthetise a patient for resection of a
phaeochromocytoma. What is a phaeochromocytoma?
A phaeochromocytoma is a functionally active, catecholamine-secreting
tumour of the neuroendocrine chromaffin cells found in the sympathetic
nervous system. They account for about 0.1% of cases of hypertension. They
are usually benign and localised to an adrenal gland. These tumours are
important to the anaesthetist because they can present unexpectedly
peri-operatively and the mortality is high.
They may secrete any combination of
Noradrenaline
Adrenaline
Dopamine
Occasionally vasoactive intestinal peptide (VIP) or ACTH.
How does it present?
The commonest presentation is sustained hypertension.
The classic presentation is of paroxysms of sympathetic crises (in 35% of cases).
Severe hypertension
Flushing
Sweating
Palpitations
Headache
Anxiety
Weakness
Lethargy
Paroxysms may be precipitated by multiple factors:
Simple activities such as exercise
Manoeuvres that increase intra-abdominal pressure such as sneezing,
voiding and defaecating.
Histamine releasing drugs and succinylcholine
Anaesthetic procedures (particularly intubatio
If undiagnosed, it may present with end-organ damage:
Presentation may be determined by the dominant catecholamine secreted:
Heart failure
Pulmonary oedema
Myocardial ischaemia
Cerebro-vascular events
Mainly noradrenaline
Hypertension, headaches,
Slow, thudding palpitations
Mainly
adrenaline Tachycardias
Anxiety attacks
Mainly
Dopamine Nausea and vomiting
Effects of adrenoreceptors
α1 Vasoconstriction
Sweating
↓ insulin and glucagon release
α2
Inhibition of noradrenaline release
β1
Chronotropy
Inotropy
Renin secretion
β2
Smooth muscle relaxation
-bronchi
-vascular wall
-uterus
↑ insulin and glucagon release
How is the diagnosis confirmed?
Clinical suspicion on the basis of history or hypertension.
Traditionally by measuring urinary catecholamines or their metabolites
(vanillylmandelic acid [VMA] and metanephrine).
Clonidine Suppression Test – lack of suppression suggests
phaeochromocytoma (prevents noradrenaline reuptake).
Genetic testing may identify familial cases.
CT can localise adrenal tumours with 93%–100% sensitivity.
MRI scan of the abdomen has a slightly higher sensitivity for extra-adrenal
tumours.
An isotope scan may help to localise an extra-adrenal tumour. A
radio-labelled iodine isotope, 123I-metaiodobenzylguanidine (MIBG), is
taken up by the chromaffin cells.
Selective vena caval sampling.
What is the 10% rule?
10% are extra-adrenal and can be anywhere a
long the sympathetic chain
from skull base to pelvis.
10% are bilateral.
10% are malignant.
10% occur in children
Are there any associations with other conditions?
- Multiple endocrine neoplasia (MEN) Syndrome Type 2
Type 2A – medullary thyroid carcinomas and parathyroid adenomas
Type 2B – medullary thyroid carcinomas and Marfanoid features.
- Von Hippel–Lindau disease
(Phaeochromocytomas, cerebellar
haemangioblastomas, and renal cell carcinoma). - Neurofibromatosis Type I (von Recklinghausen disease) –
1% incidence of phaeochromocytoma.
If you saw this person 10 weeks pre-operatively, what investigations and
treatment would you institute?
The aim of pre-operative management is to:
- Determine the site of the tumour and what it secretes.
- Normalize the blood pressure.
- Allow the resolution of catecholamine cardiomyopathy.
- Correct hypovolaemia (contracted intravascular volume).
An echocardiogram is useful to assess left ventricular function and to
exclude cardiomyopathy
ECG
a and b adrenoceptor blockade
Controls the symptoms and hypertensive swings
Reduces the hypertensive surges associated with tumour handling.
a-adrenoceptor blockade should be instituted prior to b-blockade.
Regarding B-blockers
Theoretically unopposed b blockade should be avoided.
This can block compensatory b2 vasodilatation and precipitate a hypertensive crisis.
Cardiac failure may also occur due to the reduced contractility in the
presence of a high afterload.
Selective b1-blockade is used in adrenaline secreting tumours.
NB It is not uncommon for patients to have been commenced on a
b-blocker for treatment of their hypertension, usually without adverse
effects.
Does it matter which alpha blocker you use?
Phenoxybenzamine is a non-selective a1 and a2 blocking drug
It binds covalently and irreversibly to the receptors.
It has a long duration of action and may contribute to post-operative hypotension.
a2 blocking can inhibit pre-synaptic noradrenaline re-uptake
Usually necessitates the use of B-blockade to treat secondary tachycardia
Prazosin and doxasosin are shorter acting competitive a1 selective blocking
drugs
Less tachycardia
May not require adjuvant -blockade unless the tumour is secreting
adrenaline
Do you need a cardioselective -blocker?
In theory, avoiding B2 blockade will allow B2-mediated vasodilatation to
continue but in practice a selective B1-blocker is not necessary.
B-blockers are usually added to control tachycardia secondary to a-blockade.
Selective a1-blockers may be used for adrenaline secreting tumours
or to treat the tachycardia associated with the use of phenoxybenzamine
Assuming that this patient has been adequately treated
pre-operatively, how would you anaesthetise them for laparoscopic
tumour removal?
Sedative pre-medication
Invasive arterial and central venous monitoring is essential.
Large bore i.v. access
The patient may be intravascularly depleted after prolonged sympathetic
over-stimulation.
Large fluid shifts are possible.
Cardiac output monitoring is useful in those with cardiomyopathy
Induction with remifentanil and propofol.
Remifentanil may be useful in this instance as it has short-acting sympatholytic properties.
Vecuronium to paralyse the patient to avoid the potential histamine (and
therefore catecholamine) release associated with other agents.
Intubate the patient and maintain anaesthesia with a mixture of oxygen,
air, sevoflurane and remifentanil.
Opioid-based analgesia is reasonable for a laparoscopic technique.
Thoracic epidural for an open procedure.
What drugs would you have drawn up or immediately available?
Blood pressure swings can be dramatic but transient and so the available
drugs must be potent and short-acting.
Phentolamine (a non-selective -antagonist) may be given as an infusion or
a bolus (1–2 mg increments). It acts within one circulation time.
The heart rate should be kept below 100 bpm. Short-acting -blockers such
as Esmolol or Metoprolol may be useful for this.
Magnesium blocks catecholamine release and the adrenoceptor response to
noradrenaline. It also has anti-arrhythmic activity.
Low BP?
Labetalol is a combined a and b blocker (∼1:10 : activity).
Onset in 5 minutes but effect may last hours.
There can be hypotension during these procedures too, particularly once
the tumour has been removed.
There may be profound hypovolaemia necessitating several litres of fluid.
Vasopressors such as epinephrine and metaraminol should also be
immediately available.
Surgical technique
Open lateral retroperitoneal approach
Quicker
Fewer catecholamine surges
More painful
Laparoscopic approach
Long operation
Shorter recovery time
Greater surgical manipulation – more instability.
