Editor's Comment: Dr. Julian Stewart has been researching POTS (postural orthostatic tachycardia syndrome) among adolescents with ME/CFS for well over a decade. In previous studies, he found that these adolescents suffered from “low flow” POTS, a condition in which blood flow to the lower extremities is slow. Typical symptoms of low flow POTS are decreased CO2 (hypocapnia), resulting in faintness; increased vasoconstriction, resulting in restricted blood flow; skin pallor; and tachycardia (rapid heartbeat, especially upon standing). In this study, Dr. Stewart's group found that vitamin C, administered systemically (not orally), normalized blood flow to the legs in all patients. The researchers concluded that the normalizing effect of vitamin C was due to its powerful antioxidant properties.
Ascorbate improves circulation in postural tachycardia syndrome
~Source: Am J Physiol Heart Circ Physiol. September, 2011
By Julian M. Stewart et al.
Abstract
Low flow postural tachycardia syndrome (LFP) is associated with vasoconstriction, reduced cardiac output, increased plasma angiotensin II, reduced bioavailable nitric oxide (NO), and oxidative stress. We tested whether ascorbate would improve cutaneous NO and reduce vasoconstriction when delivered systemically.
We used local cutaneous heating to 42°C and laser Doppler flowmetry to assess NO-dependent conductance (%CVCmax) to sodium ascorbate and the systemic hemodynamic response to ascorbic acid in 11 LFP patients and in 8 control subjects (aged 23 ± 2 yr). We perfused intradermal microdialysis catheters with sodium ascorbate (10 mM) or Ringer solution. Predrug heat response was reduced in LFP, particularly the NO-dependent plateau phase (56 ± 6 vs. 88 ± 7%CVCmax). Ascorbate increased baseline skin flow in LFP and control subjects and increased the LFP plateau response (82 ± 6 vs. 92 ± 6 control). Systemic infusion experiments used Finometer and ModelFlow to estimate relative cardiac index (CI) and forearm and calf venous occlusion plethysmography to estimate blood flows, peripheral arterial and venous resistances, and capacitance before and after infusing ascorbic acid. CI increased 40% after ascorbate as did peripheral flows.
Peripheral resistances were increased (nearly double control) and decreased by nearly 50% after ascorbate. Calf capacitance and venous resistance were decreased compared with control but normalized with ascorbate. These data provide experimental support for the concept that oxidative stress and reduced NO possibly contribute to vasoconstriction and venoconstriction of LFP.
Source: Am J Physiol Heart Circ Physiol. 2011 September; 301(3): H1033–H1042. Published online 2011 May 27. doi: 10.1152/ajpheart.00018.2011. Julian M. Stewart, Anthony J. Ocon, and Marvin S. Medow Department of Physiology, New York Medical College, Valhalla, New York
