Noradrenaline reactivity in patients with phaeochromocytoma before and after surgical correction

For comparable blood pressures, plasma noradrenaline is disproportionately higher in patients with phaechromocytoma than in those with essential hypertension. The 'pressor-dose' of noradrenaline or its reciprocal, the reactivity index, were abnormal in patients with phaechromocytoma before surgery and were normalized by surgical removal of the phaechromocytoma. There was a significant correlation between blood pressures and the logarithm of plasma noradrenaline concentrations. The higher dose of exogenous noradrenaline required in patients with phaechromocytoma for a given rise in blood pressure seems to be the expression of the higher levels of endogenous noradrenaline rather than true decreased reactivity.