Are the orthostatic fluid shifts to the calves augmented in autonomic failure?
BACKGROUND
In autonomic failure (AF), blood pressure (BP) falls upon standing which is commonly ascribed to defective vasoconstriction and excessive pooling. Observations on the amount of pooling in AF are contradictory.


METHODS
We evaluated pooling using strain-gauge plethysmography (SGP) during head-up tilt (HUT) with a parachute harness fixed to the tilt table to avoid muscle tension in the lower limbs and thus to maximise pooling. 23 healthy subjects and 12 patients with AF were tilted for 5 min. BP and calf volume changes, as measured by SGP, were measured continuously. Multiple regression analysis was used to examine the effect of AF on orthostatic fluid shifts after adjustment for potential confounders.


RESULTS
Patients did not differ from controls with respect to the increase of calf volume after 5 min HUT. The acute (0-1 min) and the prolonged (1-5 min) phases of calf volume responses to HUT were also similar between patients and controls. No correlation was found between the degree of orthostatic hypotension and the orthostatic calf volume change in AF. In one patient an additional measurement was made before rising from bed in the early morning demonstrating a greater albeit small increase of calf volume upon HUT.


CONCLUSIONS
Orthostatic fluid shifts at the level of the calf in AF are not augmented during the course of the day despite marked hypotension. However, a small increase of pooling may be expected when the patient first gets out of bed in the morning probably due to the absence of oedema.
Thijs
Roland D
RD
Department of Neurology and Clinical Neurophysiology, Leiden University Medical Centre, Postal Zone J3-R, PO Box 9600, 2300 RC, Leiden, The Netherlands. r.d.thijs@lumc.nl
Kamper
Adriaan M
AM
van Dijk
Arjan D
AD
van Dijk
J Gert
JG
D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D003627:Data Interpretation, Statistical; D005260:Female; D018495:Fluid Shifts / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007866:Leg / Q000098:blood supply* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology; D011187:Posture / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012791:Shy-Drager Syndrome / Q000503:physiopathology*; D013575:Syncope / Q000209:etiology / Q000503:physiopathology