Short-term intravenous phenylephrine, but not esmolol, improved orthostatic tolerance and normalized hemodynamics in POTS patients, producing significant venoconstriction (20% capacitance change).
Does short-term intravenous phenylephrine or esmolol improve orthostatic tolerance and hemodynamics in adolescents with POTS?
Intravenous phenylephrine, but not esmolol, improves orthostatic tolerance and hemodynamics in adolescents with POTS, supporting the potential use of oral alpha-1 agonists in this population.
BACKGROUND: Adrenergic agents are commonly used in the treatment of chronic orthostatic intolerance with postural tachycardia syndrome (POTS). POTS may be associated with increased limb blood flow ("high flow") and defective orthostatic vasoconstriction or decreased limb blood flow ("low flow") and potentially with small blood volume. METHODS AND RESULTS: We investigated the consequences of short-term intravenous administration of an alpha-1 adrenergic agonist, phenylephrine, and a beta-1 adrenergic antagonist, esmolol, in 14 patients with POTS aged 13 to 19 years. Indices of heart rate and blood pressure variability, peripheral blood flow, and arterial resistance were assessed, and the capacitance relation was computed for every subject using venous occlusion plethysmography. Patients were tilted to 35 degrees upright while medicated and while unmedicated, and measurements were repeated. Phenylephrine improved orthostatic tolerance and normalized hemodynamics and indices of heart rate/blood pressure variability while supine and while upright, producing significant peripheral vasoconstriction and venoconstriction (20% capacitance change). Esmolol did not improve orthostatic tolerance or hemodynamics. A subgroup of low-flow POTS patients had exaggerated venoconstriction to phenylephrine (50% capacitance change) but others had no response. CONCLUSIONS: Phenylephrine, but not esmolol, improves orthostatic tolerance and hemodynamics in POTS. This lends support to the use of oral alpha-1 agonists in the treatment of patients with chronic orthostatic intolerance.
Stewart et al. (Mon,) conducted a other in chronic orthostatic intolerance with postural tachycardia syndrome (POTS) (n=14). Phenylephrine and Esmolol vs. unmedicated was evaluated on orthostatic tolerance and hemodynamics. Short-term intravenous phenylephrine, but not esmolol, improved orthostatic tolerance and normalized hemodynamics in POTS patients, producing significant venoconstriction (20% capacitance change).