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18 Fluid Metabolism at High Altitudes
Pages 331-356

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From page 331... ... Although these changes are detectable even in those who do not exhibit any of the ill effects of high altitudes, the most florid alterations occur in those who develop high altituderelated illness (Anand et al., 1990; Bartsch et al., 1991a; Hackett et al., 1981; Hecht et al., 1959; Levine et al., 1989~. There is also evidence that subjects who develop acute mountain sickness at high altitudes may be identified prior to the onset of symptoms by distinct changes in fluid balance and in hooves regulating salt and water metabolism (B'artsch et al., 1991a; Singh et al., 1969~. Read the entire page →
From page 332... ... The second condition, adult subacute mountain sickness, occurs in adults exposed to extreme altitude and presents with severe salt and water retention without significant pulmonary hypertension (Anand et al., 1990~. Therefore, changes in fluid metabolism at high altitudes appear to have important pathogenetic implications arid merit detailed study. Read the entire page →
From page 333... ... The best data, however, come from studies of body fluid compartments using isotope dilution techniques. Table 18-1 summarizes the findings of major published studies where body fluid compartments were measured at high altitudes. Read the entire page →
From page 334... ... 334 cat i_ ._ � en ._ Ct Cat o a: ._ in so o ._ i_ en ._ Ct i_ Cat ._ Cat o as' o VO 'I 'r~: ~ ILL C: o ._ V, a l O ~ ~5 to to V Cat .s Ct on "a Ct V) Read the entire page →
From page 335... ... 335 ~ ce ~ , 3 ~ ~ ~ CuO ' ~� ~ D 5 _ ~ ~ ~ ~ C) Read the entire page →
From page 336... ... Moderate Altitudes Probably the most comprehensive human data on body fluid compartments at high altitudes come from studies on Indian soldiers (Jain et al., 1980, 1981; Singh et al., 1986, 1988, 1990~. These investigators had the unique advantage of a captive population that they could study at sea level and then again, under strict conditions of complete rest, for a period of up to 12 days after being flown to 3,500 m (11,483 ft) Read the entire page →
From page 337... ... The problem with interpreting such data is that it is not known exactly what happens to body composition as subjects lose weight at high altitudes. If weight loss is entirely due to loss of fat, then the TBW should remain unchanged but show an increase when expressed as a percent body weight. Read the entire page →
From page 338... ... They also found a shift of body fluids so that the ECV increased at the expense of the intracellular volume. This result is in sharp contrast to the findings of other authors (Hallnon et al., 1969; Jain et al., 1980, 1981; Singh et al., 1990~. Read the entire page →
From page 339... ... They found that despite the fact that the weight of these subjects continued to remain low, their TBW and ECV as a percent of body weight were greater than normal. Although this study was not made on the same subjects at sea level and high altitudes, the findings suggest that with chronic exposure to moderate altitudes, subjects are no longer hypohydrated, instead tend to retain fluid, and might eventually become hyperhydrated. Read the entire page →
From page 340... ... Prolonged stay at that altitude causes subacute mountain sickness in some subjects (Anand et al., 19903. This syndrome is characterized by severe edema, ascites, and even generalized anasarca resembling severe congestive heart failure. Read the entire page →
From page 341... ... . TBW, total body water; PV, plasma volume; PCV, packed cell volume; BV, blood volume; ERPF, effective renal plasma flow; RBF, renal blood flow; TBNa, total body sodium. Read the entire page →
From page 342... ... D~ures~s ~s common at moderate altitudes, in subjects who do not exercise soon after transfer to high altitudes, in subjects who do not develop AMS, and in subjects for whom fluid intake is strictly enforced. Diuresis is also seen in acute experiments at sea level when subjects breathe hypoxic gas mixtures (Ashack et al., 19851. Read the entire page →
From page 343... ... Most studies also showed that hypoxia attenuated the normal increase in aldosterone seen with exercise at sea level (Maher et al., 1975; Milledge et al., 1983; Olsen et al., 1992; Shigeoka et al., 1985~. Thus, although hypoxia acutely reduces aldosterone, it is not clear whether this reduction in aldosterone has a role in the acute diuresis seen at high altitudes. Read the entire page →
From page 344... ... 344 Cal ~5 ._ � ._ Ct Cal 5~ o A) Read the entire page →
From page 346... ... No AMS AMS pans Rest HA minus SL pc0.01 Exercise at Altitude FIGURE 18-7 Effect of exercise at high altitudes (HA) on aldosterone level in subjects susceptible to acute mountain sickness (AMS) Read the entire page →
From page 347... ... Both osmolality and volume status modulate its level. Changes in ADH response would be an attractive explanation for the alterations in fluid metabolism seen at high altitudes. Read the entire page →
From page 348... ... AMS FIGURE 18-8 Effect of exercise at high altitudes on antidiuretic hormone (ADH) level in subjects susceptible to acute mountain sickness (AMS) Read the entire page →
From page 349... ... level in subjects susceptible to acute mountain sickness (AMS) compared with nonsusceptible subjects. Read the entire page →
From page 350... ... These may be the mechanisms responsible for adult subacute mountain sickness reported at extreme altitudes (Anand et al., 1990, 1993) Read the entire page →
From page 351... ... Prolonged stay at extreme altitudes may cause severe salt and water retention in otherwise normal subjects. The role of hormones in normal fluid metabolism at high altitudes is unclear, but a number of hormones appear to play a role in the retention of salt and water in pathologic states like acute and subacute mountain sickness. Read the entire page →
From page 352... ... Boparai 1993 Body fluid compartments, renal blood flow, and hormones at 6,000 m in normal subjects. Read the entire page →
From page 353... ... Reeves 1981 Acute mountain sickness and the edemas of high altitude: A common pathogenesis? Respir. Read the entire page →
From page 354... ... and A Morice 1989 Atrial natriuretic peptide, altitude end acute mountain sickness. Read the entire page →
From page 355... ... Roy, and C Subramanyam 1969 Acute mountain sickness. Read the entire page →
From page 356... ... Tyagi, and K Sinha 1986 Comparative study of acetazolamide and spironolactone on body fluid compartments on induction to high altitude. Read the entire page →

From page 331...

... Although these changes are detectable even in those who do not exhibit any of the ill effects of high altitudes, the most florid alterations occur in those who develop high altituderelated illness (Anand et al., 1990; Bartsch et al., 1991a; Hackett et al., 1981; Hecht et al., 1959; Levine et al., 1989~. There is also evidence that subjects who develop acute mountain sickness at high altitudes may be identified prior to the onset of symptoms by distinct changes in fluid balance and in hooves regulating salt and water metabolism (B'artsch et al., 1991a; Singh et al., 1969~.

18 Fluid Metabolism at High Altitudes Pages 331-356

18 Fluid Metabolism at High Altitudes
Pages 331-356