Older adults experienced significant hypotension (change in MAP -7 +/- 2 mmHg) at the onset of orthostatic challenge due to a diminished heart rate response compared to younger adults.
Does vagal dysfunction contribute to orthostatic hypotension at the onset of orthostatic challenge in older adults?
Elderly individuals experience orthostatic hypotension at the onset of orthostatic challenge due to a diminished heart rate response, likely related to vagal dysfunction.
We tested the hypothesis that hypotension occurred in older adults at the onset of orthostatic challenge as a result of vagal dysfunction. Responses of heart rate (HR) and mean arterial pressure (MAP) were compared between 10 healthy older and younger adults during onset and sustained lower body negative pressure (LBNP). A younger group was also assessed after blockade of the parasympathetic nervous system with the use of atropine or glycopyrrolate and after blockade of the beta(1)-adrenoceptor by use of metoprolol. Baseline HR (older vs. younger: 59 +/- 4 vs. 54 +/- 1 beats/min) and MAP (83 +/- 2 vs. 89 +/- 3 mmHg) were not significantly different between the groups. During -40 Torr, significant tachycardia occurred at the first HR response in the younger subjects without hypotension, whereas significant hypotension change in MAP (DeltaMAP) -7 +/- 2 mmHg was observed in the elderly without tachycardia. After the parasympathetic blockade, tachycardiac responses of younger subjects were diminished and associated with a significant hypotension at the onset of LBNP. However, MAP was not affected after the cardiac sympathetic blockade. We concluded that the elderly experienced orthostatic hypotension at the onset of orthostatic challenge because of a diminished HR response. However, an augmented vasoconstriction helped with the maintenance of their blood pressure during sustained LBNP.
Shi et al. (Sun,) conducted a other in Orthostatic hypotension. Lower body negative pressure (LBNP) with or without autonomic blockade vs. Younger adults was evaluated on Heart rate and mean arterial pressure responses. Older adults experienced significant hypotension (change in MAP -7 +/- 2 mmHg) at the onset of orthostatic challenge due to a diminished heart rate response compared to younger adults.