Editing Adrenal: Pheochromocytoma (section)

==== Pre-operative medications ====
* '''Indications'''
**'''<span style="color:#ff0000">All patients with pheochromocytoma and an abnormal metabolic evaluation undergo preoperative catecholamine blockade, including patients who do not exhibit evidence of blood pressure elevation and lack classic symptomatology.'''
*** '''Catecholamine release during intraoperative tumor manipulation can result in hazardous blood pressure elevation and cardiac arrhythmias.'''
*** Recent data suggest that preoperative α-blockade may not be necessary in normotensive asymptomatic patients
* '''<span style="color:#ff0000">α-Blockade'''
** '''Helps in both hemodynamic and glucose control'''
** '''<span style="color:#ff0000">Phenoxybenzamine'''
*** '''Most common α- blocker used for preoperative catecholamine blockade of pheochromocytoma.'''
*** '''MOA: irreversible, non-selective α receptor blocker'''
**** Intraoperative catecholamine surges typically do not override its actions, because reversal of the blockade is possible only through synthesis of new receptor molecules.
**** Non-selective nature '''may lead to tachycardia and β-adrenergic blockade may be necessary'''
**** '''Prolonged hypotension in the immediate postoperative period and central nervous system effects such as somnolence may be expected'''
**** '''Newer selective and competitive α1-adrenergic blockers such as doxazosin, prazosin, and terazosin obviate the drug-induced need for β-blockade.'''
*** '''<span style="color:#ff0000">Started 7-14 days before surgery.'''
**** Can be started at 10 mg twice daily with a stepwise increase of 10 to 20 mg every 2 to 3 days until a final dose of 1 mg/kg if tolerated.
***** During this time blood pressure checks should be conducted at least 3 times a day.
***** The last dose of phenoxybenzamine is usually given on the night before surgery, and the next morning’s dose is withheld to minimize potentially prolonged hypotension after tumor resection.
*** '''If phenoxybenzamine not effective for blockade, start metyrosine'''
**** MOA of metyrosine: blocks the biosynthesis of catecholamines by inhibiting the conversion of tyrosine to L-dopa
**** Generally added for extensive disease with large increases in catecholamines.
*** Acute hypertensive attacks can also be treated with a short-acting alpha blocker such as phentolamine.
* '''<span style="color:#ff0000">β-blockade'''
** '''Must be given with caution in patients with myocardial depression'''
** '''<span style="color:#ff0000">Should never be started before appropriate α-blockade'''
*** '''In the absence of α-blockade, β antagonists cause a potentiation of the action of epinephrine on the α1 receptors, resulting in hypertension''', owing to blockade of the arteriolar dilation at the β2 receptor. For this reason, '''selective β1 adrenoreceptor blockers, such as atenolol and metoprolol, are usually preferred.'''
** '''<span style="color:#ff0000">May be added when (2)'''
**# '''<span style="color:#ff0000">Systolic blood pressure is <100 mmHg'''
**# '''<span style="color:#ff0000">Tachycardia or reflex tachycardia develops.'''
* Calcium channel blockers
** Some studies report that sole use of calcium channel blockers is sufficient for safe pheochromocytomas resection. This approach avoids the reflex tachycardia and postoperative hypotension that are seen with use of phenoxybenzamine. This strategy be reserved for patients who are normotensive with paroxysmal hypertension and a normal baseline blood pressure.
** Usually, preoperative calcium channel blockade for 2 weeks is sufficient.