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No renal dysfunction or salt and water retention in acute mountain sickness at 4,559 m among young resting males after passive ascent.

PURPOSE
This study examined the role and function of the kidney at high altitude in relation to fluid balance and the development of acute mountain sickness (AMS), avoiding confounders that have contributed to conflicting results in previous studies.


METHODS
We examined 18 healthy male volunteers (18 - 40 years) not acclimatized to high altitude while on a controlled diet and resting recumbently for 24 h at Lausanne (altitude: 560 m) followed by a period of 44 hours after reaching the Regina Margherita hut (4,559 m) by helicopter.


RESULTS
AMS scores peaked after 20 h at 4,559 m. AMS was defined as functional Lake Louise score > 0. There were no significant differences between 10 subjects with and 8 subjects without AMS for urinary flow, fluid balance and weight change. Sodium excretion rate was lower in those with AMS after 24 h at altitude. Microalbuminuria increased at altitude but not differently between the groups. Creatinine clearance was not affected by altitude or AMS, while sinistrin and PAH clearances decreased slightly, more markedly in those without AMS. Plasma concentrations of epinephrine, norepinephrine, atrial natriuretic factor and vasopressin increased while renin activity, angiotensin and aldosterone decreased at altitude. Hormones levels did not differ between those with and without AMS.


CONCLUSIONS
1) Renal function is not affected by hypoxia at 4,559 m in resting subjects except for minor microalbuminuria, 2) high altitude diuresis does not occur and 3) AMS is not associated with salt and water retention or renal dysfunction.