Cardiovascular and sweating responses to water ingestion during dehydration

Abstract

The experiments reported are concerned with cardiovascular and sudomotor events preceding, accompanying, and following ingestion of water by five dehydrating subjects 8.75 hr after entrance into a heat chamber (43.3 C DB, 29 C WB). Certain skin areas such as the cheek showed increases in evaporative heat loss before subjects came in contact with water. This reflex could be initiated by saline ingestion but the degree of skin and oral temperature changes appeared to depend on tonicity of fluid ingested. The gustatory reflex was not thought to be the initiating agent for sudomotor responses. Increases in cutaneous blood flow appeared to begin almost as promptly as sweating responses but took considerably longer to develop. Ingestion of saline, though initiating a sweating response, did not alter heart rate, blood pressure, or cutaneous blood flow. It is suggested that fluid ingestion, regardless of tonicity, triggers reflex sweating over the body surface. Intensity and duration of this sudomotor response, as well as initiation of cardiovascular changes, apparently depend on tonicity of ingested fluid. cutaneous blood flow; skin temperature; regional sweating Submitted on November 27, 1964

Evidence that transient changes in sudomotor output with cold and warm fluid ingestion are independently modulated by abdominal, but not oral thermoreceptors

“…Nonthermal modifiers of the central drive for sweating have been previously shown with fluid ingestion. The act of drinking temporarily inhibits the osmoregulatory inhibition of sudomotor activity in dehydrated subjects, with the ingestion of a small (ϳ4 ml/kg of body wt) aliquot of 38°C fluid eliciting an immediate rise in sweating (12,22,25). However, when subjects are euhydrated or isoosmotic, this nonthermal reflex sweating response is abolished (25).…”

Effect of water ingestion on cardiovascular and thermal responses to prolonged cycling and running in humans: a comparison

“…Accumulated knowledge on this issue, from the early study of Senay and Christensen (1965) until recently (Gonza´lez-Alonso et al 2000), is based on research mainly conducted on the cycle ergometer Candas et al 1986;Hamilton et al 1991;Montain and Coyle 1992a, b;McConell et al 1997). Only a limited number of studies have examined the effect of fluid ingestion on physiological responses to other exercise modes such as running (Gisolfi and Copping 1974;Fallowfield et al 1996;Montain et al 1998;Morris et al 1998), despite the facts that:…”

Drinking-induced thermoregulatory panting in rehydrated sheep: influences of oropharyngeal/esophageal signals, core temperature, and thirst satiety

“…It has long been known that the drinking of water results in an immediate sweating response in hyperthermic dehydrated human subjects (14,20,23), while panting increases to even higher levels following drinking to rehydration in dogs and goats exposed to a hot environment of 40°C (2,4). In the latter studies, rehydration was achieved by the animals drinking either water or isotonic saline (temperature of 38°C).…”