Age and Ageing, Vol 28, 522-530, Copyright © 1999 by British Geriatrics Society
MA James and JF Potter
BACKGROUND: orthostatic hypotension in elderly people is often attributed
to diminished afferent baroreflex sensitivity, but this has not been
demonstrated. We examined the hypothesis that postural change in blood
pressure is related to baroreflex sensitivity, independent of the
confounding effect of baseline blood pressure. METHODS: we studied 25
active, untreated elderly subjects free of postural symptoms (mean age 70
+/- 1 years): 16 with hypertension (clinic blood pressure 194 +/- 6/98 + 3
mmHg) and nine normotensive controls (clinic blood pressure 134 + 3/77 + 3
mmHg). We assessed baroreflex sensitivity from the heart rate and blood
pressure responses to the Valsalva manoeuvre and a pressor and depressor
stimulus (bolus phenylephrine injection or sodium nitroprusside infusion
respectively). Subjects were then passively tilted to 60 degrees and
maximum changes in systolic blood pressure, heart rate, forearm blood flow
and forearm vascular resistance recorded. RESULTS: maximum change in
systolic blood pressure with head- up tilt was correlated with supine
systolic blood pressure (r = 0.60, P = 0.001). Maximum change in systolic
blood pressure with orthostasis was greater in the hypertensive subjects
(45 +/- 4 mmHg versus 29 +/- 6, P = 0.04) and the heart rate increment was
less (16 +/- 2 bpm versus 24 +/- 4, P = 0.02). The increase in forearm
vascular resistance with tilt was similar in the two groups (47 +/- 11
versus 38 +/- 7 units, P = 0.52). All three methods of assessing baroreflex
sensitivity showed a reduction in the hypertensive subjects (all P < or
= 0.02). Lower values of baroreflex sensitivity were related to greater
falls in systolic blood pressure with tilt, after adjustment for the
baseline level of systolic blood pressure. CONCLUSIONS: we found a
relationship between baroreflex sensitivity and the systolic blood pressure
fall with orthostasis, even after adjustment for prevailing systolic blood
pressure. Despite equivalent changes in forearm vascular resistance with
tilt, greater falls in systolic blood pressure were seen in hypertensive
subjects than in normotensive controls, due in part to an inadequate
baroreflex-mediated heart rate response. The postural fall in blood
pressure often observed in elderly hypertensive subjects may be related to
the reduced baroreflex sensitivity seen in this condition.
ARTICLES
Orthostatic blood pressure changes and arterial baroreflex sensitivity in elderly subjects
University Department of Medicine for the Elderly, Glenfield Hospital, Leicester, UK.
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