Supportive therapy focuses on decreasing symptomatic OH and syncope. Such therapy would include physical countermaneuvers, including compression garments and dietary changes
(increased salt, rapid water drinking). Supportive drug therapy often aims to increase blood volume by promoting salt and water retention (fludrocortisone) or by increasing red blood cell mass (recombinant erythropoietin) [
55]. Defects in erythropoietin may occur as part of the denervation in autonomic failure [
63]. Short-acting pressor drugs such as midodrine or drugs that enhance autonomic activity (atomoxetine, yohimbine or pyridostigmine) are also used [
55,
64].
Rapid water ingestion of approximately 16 ounces deserves special mention. Studies in adults have demonstrated that intake of water free of solute can increase BP and improve sympathetic vasoconstriction after a sufficient time has elapsed for the water to reach the small intestine, approximately 20 min [
65]. The therapeutic effect of water encompasses all OI, including OH, POTS and VVS [
66] and can be successfully used to prevent blood phobic VVS. Effects last for several hours. The mechanism is dependent on osmolarity and may depend on TRPV4 C-fiber receptors within the portal system [
67]. This is a very important, simple and effective palliation that is not often considered by clinicians.