Veno-arterial extracorporeal membrane oxygenation for pheochromocytoma-related shock: treat cause and consequence
Abstract
Pheochromocytoma (PC) and paraganglioma (PG) are neuroendocrine tumours derived from chromaffin cells. While PCs are located in the adrenal medulla, PGs are extra-adrenal para-aortic tumours, both with masses up to 7-10 cm.
Both PC and PG (PCPG) typically present with hypertension, headache, sweating and palpitations, with sudden onset and often paroxysmal nature.1 However, PCPG may also be silent, or be uncovered in patients with otherwise unexplained abdominal pain. Metastasis may occur in an estimated 10% of patients.
PCPG are probably largely underdiagnosed and incidental PCPG are not rare in autopsies.2 In around 0.5% of patients with arterial hypertension, PCPG can be uncovered3 - often without hypertensive emergency, as a proportion of PCPG frequently shows rather constant catecholamine secretion in contrast to the classic paroxysmal excess. Diagnosis relies on measurement of catecholamine metabolites (metanephrines) in serum or urine and abdominal computed tomography (CT) or magnetic resonance imaging (MRI), and treatment aims at surgical resection of the tumour.
PCPG may lead to so-called PC or PG 'crisis', which may be hypertensive emergency or shock with profound hypotension.4 The spectrum of PCPG crisis is wide and comprises cardiogenic and/or vasoplegic shock, potentially including dysfunction of all major organ systems.5 The pathophysiological mechanism of shock in the presence of a catecholamine-secreting tumour is still incompletely understood. Patients presenting to hospitals with shock and PCPG are frequently hypovolemic with intravascular volume depletion, which is assumed to be induced by catecholamine excess.6 One explanation is catecholamine-associated heart failure, and indeed a large proportion of patients develops Takotsubo syndrome (TS), which is indistinguishable from TS related to other triggers in terms of ventricular wall motion abnormalities.
However, PCPG may also lead to severe global cardiac failure. Another reason may be the acute pharmacological treatment of hypertensive crisis, for example with phentolamine, which may equally contribute to shock development later on.
PCPG crisis may further be induced by surgical manipulation or removal of the tumour, or other mechanical irritation such as pregnancy or delivery, or by hemorrhagic transformation.