Prevalence and etiology of delayed orthostatic hypotension in adult women.

OBJECTIVE: To evaluate the contributing roles of venous status, microvascular filtration, and calf muscle pump activity in the etiology of delayed orthostatic hypotension (OH). DESIGN: Unblinded within-subjects trial. SETTING: Academic clinical research center. PARTICIPANTS: Convenience sample of healthy adult women (N=30) with an age range of 30 to 65 years. INTERVENTION: Plantar micromechanical stimulation applied at a 45-Hz frequency and a 50-microm amplitude for a duration of 30 minutes during upright sitting. MAIN OUTCOME MEASURE: Diastolic blood pressure (DBP). RESULTS: White women (mean age, 51.8+/-1.3 y) were recruited and screened for delayed OH. About one quarter (9/33) of the screened subjects showed delayed OH as determined by a significant decrease in blood pressure after at least 15 minutes of quiet sitting. Air plethysmographic assessment provided no evidence of venous insufficiency (venous filling index, >2.5 mL/s; venous volume, >80 mL) or excessive microvascular filtration in the affected subjects, whereas activation of the calf muscle pump (CMP) through plantar-based micromechanical stimulation consistently resulted in a significant increase in systolic blood pressure (SBP) (DeltaSBP=22.8+/-3.9 mmHg, P=.003) and DBP (DeltaDBP=20.9+/-3.3 mmHg, P=.002). CONCLUSIONS: About 25% of the adult women studied showed delayed OH during quiet sitting and the proximate cause appears to be neuromuscular in origin, specifically inadequate calf muscle tone, because venous and microvascular filtration status is normative in the delayed OH subpopulation and CMP stimulation reverses the hypotension.

Reversal of lower limb edema by calf muscle pump stimulation.

BACKGROUND: Peripheral edema (PE) is commonly coupled with heart failure, restrictive cardiomyopathy, nephrotic syndrome, renal failure, and hypoproteinemia. Diuretics and/or limb elevation, although commonly prescribed to treat PE, are often insufficient to remove sufficient fluid to prevent complications. We assessed the ability of the calf muscle pump (CMP) stimulation to reverse PE. METHODS: Fluid volume was evaluated by air plethysmography in the right legs of 54 adult women (mean age 46.7 +/- 1.5 years) following venous status assessment. Change in calf volume was assessed during 30 minutes of quiet sitting, followed by 30 minutes of sitting with CMP stimulation via micromechanical stimulation of the plantar surface. RESULTS: Leg volume changes demonstrated a bimodal distribution. Leg volume decreased during quiet sitting in 56% of the study group, whereas in 44% of the group, significant lower leg fluid pooling was evident (increase in calf volume of 14.0 +/- 0.3 mL/h). CMP stimulation reversed the fluid pooling in the edematous group (-2.7 +/- 0.1 mL/h) and was able to accelerate fluid removal in the nonedematous group. CONCLUSIONS: Approximately two fifths of adult women experience substantial pooling when their lower limbs are maintained in a dependent position. Lower-extremity edema exhibited by these women may primarily be due to inadequate calf muscle tone because exogenous stimulation of the CMP was sufficient to halt and reverse fluid pooling. Whether CMP stimulation would provide a means to treat PE in individuals with edema-related health complications, such as congestive heart failure, merits further investigation.