Case 17: Pheochromocytoma

Question 1

How is pheochromocytoma diagnosed?

Answer 1

Pheochromocytoma should be suspected when a patient

1. is experiencing signs and symptoms associated with excessive secretion of catecholamine (norepinephrine, epi, dopamine); HTN, diaphoresis, headache, tachycardia
2. Hypertension that is difficult to control
3. Family history of pheochromocytoma
4. Unexpected pressor response to drugs such as histamine, glucagon, reglan

PHE-ochromocytoma; Palpitations, Headache, Episodic Sweating most common signs

When pheochromocytoma is suspected there are a number of tests available to establish diagnosis

1. Measurement of free metanephrines in plasma
2. Measurement of total urinary catecholamines
3. Urinary metanephrines
4. Urinary vanillylmandelic acid

Once diagnosis achieved localization with MRI appropriate

Question 2

How would you evaluate and optimize a patient with pheochromocytoma pre-operatively?

Answer 2

• Ensure adequate alpha adrenergic blockade atleast 7-10 days prior to surgery in order to eliminate symptomatology - (Phenoxybenzamine, Phentolamine)
• Administer fluids to restore intravascular volume status
• further evaluate cardiac status w/ focused history - CXR, EKG, ECHO
• Initiate beta blockade to optimize heart rate
• Optimize pulmonary function
• Consider sedatives, analgesics to reduce anxiety and minimize catecholamine surge

Question 3

Drug that should be avoided in pheochromocytoma case

Answer 3

Druugs that should be avoided, if possible, during the case include those that:

1. Simulate tumor cells, such as succinylcholine (abdominal fasciculations) and histamine releasing drugs (morphine, atracuronium, succinylcholine)
2. Result in increased sympathetic activity such as ephedrine
3. Sensitize the myocardium to catecholamines, such as halothane
4. Droperidol, metoclopramide, and ephedrine should also be avoided if possible since that have all been associated with significant hypertension when administered to patients with pheochromocytoma.

Question 4

Why are patients with pheochromocytoma at increased risk of post operative hypoglycemia?

Answer 4

• Drop in plasma catecholamines results in increased release of insulin (stimulation of alpha 2 receptors on pancreatic beta cells by epi and norepi inhibits release of insulin) and reduced gluconeogenesis and glycogenolysis (epinephrine stimulates the precesses that serve to increase blood sugar)
• Therefore fluid replacement following tumor removal should include dextrose containing solutions and patient’s blood sugar should be monitored closely.