Pheochromocytoma Crisis

Pheochromocytomas arise from chromaffin cells in the adrenal medulla; related extra-adrenal tumours are paragangliomas. Both may release norepinephrine, epinephrine, and occasionally dopamine. The acute syndrome is caused by the effect of these hormones on adrenergic receptors, not by the physical size of the tumour. Norepinephrine-driven alpha-1 stimulation produces intense vasoconstriction, pallor, and abrupt blood-pressure elevation. Beta-1 stimulation increases heart rate and contractility, raising myocardial oxygen demand and provoking dysrhythmias. Catecholamines also alter glucose metabolism, so marked hyperglycaemia may accompany an attack. The familiar pattern is episodic headache, pounding palpitations, diaphoresis, pallor, and anxiety with labile or sustained hypertension. A patient does not need to display the entire pattern. A crisis is the point at which catecholamine excess causes haemodynamic instability or organ injury. One pattern combines instability with multiorgan dysfunction: hypertensive encephalopathy, myocardial ischemia or infarction, acute heart failure, pulmonary edema, dysrhythmia, renal injury, or DIC may develop. Another pattern is sustained hypotension, sometimes with shock; this hypotensive presentation has been associated with mortality of approximately 28%. A patient can therefore be critically ill with PPGL while the blood pressure...