Background: Arginine vasopressin (AVP) changes during altitude acclimatization is of clinical interest as increases in their plasma levels (with reference to sea-level (SL)) have been associated with fluid retention accompanied by elevated plasma cortisol levels. Studies have reported no change/ decrease in plasma AVP during normal acclimatization. This study was conducted to evaluate plasma AVP changes and the associated physiological changes during chronic exposure to high-altitude (HA).
Methods: Healthy, male volunteers (n=36) between 2050 years of age were recruited for the study. Subjects were evaluated both at SL and HA (4500 m, 34 weeks of stay) for the following parameters: plasma cortisol (CORT) and AVP (ELISA), haemoglobin(Hb), hematocrit(Hct), plasma sodium (Na); total protein (PROT), body weight (BW), arterial oxygen saturation (SaO2), heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP). Values are mean±S.D.
Results: At HA, all subjects were asymptomatic and exhibited physiological characteristics of altitude acclimatization (↓: BW, SaO2; ↑: Hb, Hct, MAP, HR; ↔: RR). Plasma AVP and CORT level during HA exposure was within SL normal range. Subjects were categorized as follows:
|Category AVPSLvsHA||n||SL||HA||P value||SL||HA||P value||PROT/Na|
Conclusions: Altitude acclimatization is characterised by physiological variation in both plasma AVP and CORT levels. However, the significance of subtle changes in AVP with regard to body fluid regulation (re-setting of osmotic threshold) needs further evaluation.