Cardiovascular responses to infused epinephrine: effect of the state of physical conditioning

Arterial pressure and heart rate responses to intravenous infusions of epinephrine at rates of 4-64 ng/kg/min were determined in 15 healthy subjects. The state of physical conditioning in these subjects was assessed by resting (preinfusion) heart rate and bicycle ergometry. Predicted maximal oxygen consumption (pMVO2) was determined by performance at submaximal work loads. Significant correlations were observed between both preinfusion heart rate and pMVO2 and the threshold for the effect of epinephrine on systolic pressure, and the magnitude of the increase in systolic pressure. Neither preinfusion heart rate nor pMVO2 correlated significantly with the chronotropic effect of epinephrine (threshold or absolute increase in heart rate). The pMVO2 and preinfusion heart rate did not correlate significantly with preinfusion venous plasma epinephrine concentration or with plasma levels achieved during infusion. We conclude that physical conditioning increases the effect of circulating epinephrine on systolic arterial pressure without altering the chronotropic effect of this hormone.