Pheochromocytoma Flashcards
What is the differential diagnosis of Arterial hypertension?
Essential HPT primary renal disease Endocrine Sympathetic stimulation Miscellaneous
What is pheocromocytoma?
Tumors of the cheomaffin cells secreting noradrenaline, adrenaline or dopamine.
They Amy secrets >1 amine.
What other substances may theae tumors produce?
VIP
ACTH
Where are they usually situated?
Adrenal medulla 99%
Sympathetic paraganglua
May extend to from base of skull to anus
Prevalence of pheo
0.005%-0.01%
Both genelders
Incidence at peak 3rs - 5th decade of life
Which age group do they commonly occur?
Occurs in all ages but less common in children.
10 rule of pheo?
10% bilateral
10% familial
10% extrarenal
10% malignant
Which familial syndromes is Pheo associated with?
MEN2A: parathyroid adenama, medullary thyroid carcinoma, pheo
MEN2B: medullary carcinoma of thyroid, mucosa adenoma, marfanoid features, pheo
Hippel-Lindau Syndrome : haemangioma of retina, cerebellum, pheo
Neurofibromatosis : neurofibromas, cafe-au-lait spots, axillary or inguinal freckling, optic nerve glioma, pheo
What’s the presentation of pheo?
Hypertension
Palpitations, sweating headaches with HPT
Acute presentations includes: MI, pulmonary oedema, CVA
What biochemical tests can be done for diagnosis of pheo?
Vanillylmandelic acid
Urine Metanephrines - high tru e-positive results 98-99%
Plasma Metanephrines- more difficult to implement correctly
What radiological tests can be used to diagnose Pheo?
CT with or without iodine 131 labeled metqiodobenzylguanidine.
CAUTION : radio Contrast induces a pheo crisis as iodine taken up by cheomaffin tissue.
MRI in pregnancy and extrarenal
What additional investigation are needed for anaesthesia?
ECHO: hx if MI or signs of failure
Blood glucose
Preoperative : how is the pharmacological preparation done?
Alpha blockers: Phenoxybenzamine, doxazocine, prazocine, terazocine
Preoperative ;
phenoxybemzamine
Long duration
Easy to administer
Irreversibly and non selectively binds aplha 1
SE:
Phenoxybenzamine SE
Reflex tachycardia therefore a B Blocker is introduced when aplha blockade is achieved
Why is b Blocker not advised before adequate A blockade
Inhibition of b receptors mediated Vasodilation can result in unopposed A receptor mediated vasoconstriction due to catecholamines secreted by tumor which can precipitate Hypertensive crisis, heart failure and end organ damage.
What other medications can be used preoperatively
Methyl-para-tyrosine - inhibits enzyme tyrosine hydroxylase thus reduces production of catecholamines
Calcium channel Blockers- nicardipine maybe equivalent to Phenoxybenzamine
How is sympathetic blockade assessed
BP < 140/90 HR<100bpm
Erect and supine HR & BP should exhibit a marked postural drom of >20mmhgwith compansated tachycardia
What are the main goals of preoperative pharmacological therapy?
Control hypertension
Facilitate intravascular volume : patient oral fluid and salt intake
Perioperative: premedication
Required ie temazepam
Preoperative monitoring
Standard ASA: V5 lead, core temperature A-Line CVP + large bore CO monitor Urine catheter.
Best induction agents to use
Propofol
Rami
Rapifen
Vec or roc
Drugs to avoid
Droperidol Morphin Atracurium Pancuronium Ketamin Ephedrine Halothane Cocain Metoclopromide
Management of hypertension intraop: Mgso4
Can be started prior induction 2-4g bolus with 1-2g/hr infusion.
Blockers catecholamines release, block receptors, vasodilates and myocardial protectant
