Norepinephrine and epinephrine responses during orthostatic intolerance inhealthy elderly men

In young individuals, orthostatic intolerance is associated with marked inc reases in plasma epinephrine (EPI) concentrations and attenuated rises in p lasma norepinephrine (NE) concentrations. This study investigated the cardi ovascular, EPI and NE responses of healthy elderly males during orthostatic stress. Twelve men (68 +/- yr) with a recent history of orthostatic hypote nsion and who exhibited orthostatic intolerance (HYPO) during 90 degrees he ad-up tilt (HUT) were compared with 12 men (69 +/- yr) without a history of orthostatic hypotension and who remained normotensive (NORMO) throughout 9 0 degrees HUT. Beat-by-beat recordings of heart rate (HR), mean (MAP), syst olic (SBP), diastolic (DBP), and pulse (PP) pressures were made throughout 90 degrees HUT. Blood samples obtained during supine rest and 90 degrees HU T were analyzed for changes in EPI and NE concentrations, hematocrit, hemog lobin and plasma volume. Compared to supine rest, orthostatic intolerance w as characterized by significant reductions (p < 0.0001) in MAP, SEP, DBP, a nd PP. The HR, MAP, SEP, DBP, and Pf at the termination of 90 degrees HUT w as significantly lower (p < 0.0001) for HYPO than NORMO. The 90 degrees HUT position resulted in significant increases (p < 0.01) in NE for both HYPO and NORMO, with the rise in NE significantly lower (p < 0.05) in HYPO. Ther e were no differences between groups regarding EPI concentrations at the te rmination of 90 degrees HUT. These results suggest that the magnitude of ar terial pressure (AP) reduction does not influence the EPI response during o rthostasis in healthy elderly men. However, marked reductions in AP, leadin g to orthostatic intolerance, are associated with inadequate increases in N E in these individuals.