Cyclic blood pressure changes in a patient with a phaeochromocytoma: role of a central oscillator?

During continuous intra-arterial pressure monitoring in an 18-year-old man with severe hypertension and a phaeochromocytoma we registered marked oscillations in blood pressure with a cycle length of 3 min (range 2-4 min) and amplitude of 40 mmHg (range 12-80 mmHg). Changes in heart rate were opposite to changes in pressure. The pressure waves almost invariably appeared at rest and were most prominent during sleep. Plasma levels of noradrenaline were between 180-240 nmol/l but failed to show cyclic fluctuations. Plasma adrenaline and dopamine were normal. The waves disappeared during blockade of ganglionic nerve transmission (trimetaphan) and finally after surgical removal of the tumour. A cerebral ischaemic pressor response related to local vasoconstriction and leading to baroreflex mediated feedback oscillation of sympathetic neuron activity might be responsible for these pressure waves. A central oscillator mechanism somehow amplified by high circulating noradrenaline is another possibility.