The osmopressor response to water drinking
ABSTRACT Water drinking elicits profound pressor responses in patients with impaired baroreflex function and in sinoaortic-denervated mice. Healthy subjects show more subtle changes in heart rate and blood pressure with water drinking. The water-induced pressor response appears to be mediated through sympathetic nervous system activation at the spinal level. Indeed, water drinking raises resting energy expenditure in normal weight and obese subjects. The stimulus setting off the response is hypoosmolarity rather than water temperature or gastrointestinal stretch. Studies in mice suggest that this osmopressor response may involve transient receptor potential vanniloid 4 (Trpv4) receptors. However, the (nerve) cell population serving as peripheral osmosensors and the exact transduction mechanisms are still unknown. The osmopressor response can be exploited in the treatment of orthostatic and postprandial hypotension in patients with severe autonomic failure. Furthermore, the osmopressor response acutely improves orthostatic tolerance in healthy subjects and in patients with neurally mediated syncope. The phenomenon should be recognized as an important confounder in cardiovascular and metabolic studies.
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ABSTRACT: Post-exercise heart rate recovery is an easy-to-apply index which reflects the post-exercise vagal reactivation. Water intake produces significant changes on the cardiovascular system, promoting an increase in heart vagal modulation. The aim of this study was to investigate the influence of water intake on the heart rate recovery. Ten healthy subjects of both genders were enrolled in this study. The experimental session consisted of performing cyclergometer exercise, water intake and heart rate recovery recording. There was also a control session. From the heart rate values of exercise and recovery the deltas of 60 and 120 seconds of recovery were calculated and compared between the "water intake" and "control session" conditions. Greater delta values of 120 seconds to recover on "water intake" condition in relation to the control session were observed. The water intake accelerates the post-exercise heart rate recovery.Revista da Educação Física/UEM 12/2011; 23(2):271-276.
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ABSTRACT: Introduction: Syncope is an abrupt loss of consciousness in response to reduced perfusion to the brain. Neurocardiogenic or vasovagal syncope results from a complex neurologic reflex, and treatments to prevent recurrence attempt to modulate aspects of that reflex. Areas covered: Pharmacologic treatments for vasovagal syncope address the syncope reflex in multiple ways. Fludrocortisone and sodium chloride increase systemic fluid volume. Midodrine, β blockers and norepinephrine transport inhibitors modulate the sympathetic nervous system. Other treatments for syncope modulate other neurotransmitters or affect heart rate. The most recent trials evaluating established and novel therapies are reviewed. Expert opinion: To reduce recurrence of vasovagal syncope, conservative measures are first line. If these fail to prevent recurrence, the most promising medical therapy includes midodrine. Randomized placebo-controlled data evaluating fludrocortisone, midodrine and β blockers in older patients are awaited. Because of the significance of the placebo effect in this condition, any treatment must be evaluated in a randomized double-blind placebo-controlled trial before being accepted as effective.Expert Opinion on Pharmacotherapy 12/2014; DOI:10.1517/14656566.2015.996129 · 3.09 Impact Factor
Article: Management of young blood donors.[Show abstract] [Hide abstract]
ABSTRACT: The emphasis on high-school blood drives and acceptance of 16-year-old blood donors led to more research on physiologic and psychological ways to decrease vasovagal reaction rates in young blood donors and to increase donor retention. Research on how to accomplish this has been advantageous for the blood collection industry and blood donors. This review discussed the current situation and what can be done psychologically, physiologically, and via process improvements to decrease vasovagal reaction rates and increase donor retention. The donation process can be significantly improved. Future interventions may include more dietary salt, a shorter muscle tension program to make it more feasible, recommendations for post-donation muscle tension / squatting / laying down for lightheadedness, more donor education by the staff at the collection site, more staff attention to donors with fear or higher risk for a vasovagal reaction (e.g. estimated blood volume near 3.5 l, first-time donor), and a more focused donation process to ensure a pleasant and safer procedure.Transfusion Medicine and Hemotherapy 07/2014; 41(4):284-95. DOI:10.1159/000364849 · 2.01 Impact Factor