We present a patient with an adrenal pheochromocytoma with an unusual pattern of periodic alternating hypertension and hypotension. Alpha-adrenergic blockade alone failed to affect this pattern, which was abolished only after fluid repletion. The efficacy of volume expansion in ultimately correcting the wide fluctuations of blood pressure implicates a possible reflex neurogenic mechanism for the cyclic changes in blood pressure attributable to intravascular volume contraction. (Hypertension 6:

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... 81-284, 1984) KEY WORDS • adrenal • pheochromocytoma adrenergic blockade • catecholamines • hypertension E PISODIC rises in blood pressure in patients harboring pheochromocytoma are well known. 1 However, rapidly occurring cyclical hypertension alternating with hypotension in such patients has rarely been documented. 2 3 In one report, a catecholamine-secreting glomus jugulare tumor was associated with such a response. 3 We report here a similar response in a patient with an adrenal pheochromocytoma. Alpha-adrenergic blockade with phentolamine alone did not control the blood pressure fluctuations, which finally abated only when volume replacement was instituted. Case Report History This 67-year-old man had diabetes mellitus for 15 years. Two years earlier he had been admitted to a hospital for evaluation of precordial pain, episodes of sweating, weakness, and dyspnea associated with marked bradycardia. He was felt to have "sick sinus syndrome" and a permanent pacemaker was placed. Even after the placement of the pacemaker he contin-