title: Changes of hematocrit and hemoglobin concentration in the cold Himalayan environment in dependence on total body fluid.
abstract: BACKGROUND
  The organism is exposed to a considerable hypoxic stress at high altitude, and the well-known polyglobulia is an effective strategy to sustain oxygen delivery to the tissue at reduced saturation of hemoglobin. In general, an increasing erythropoiesis is thought to be the reason, although this increase of red blood count can be observed after a short time of altitude exposure and the parameters are expressed as water-depending concentrations. Therefore, the influence of water distribution on hemoglobin (Hb) and hematocrit (Hct) values during a long-term exposure at high altitude was investigated.
  
  
  METHODS
  Measurements were performed in 12 mountaineers before, during, and either 7/8 or 11/12 days after a Himalaya expedition (26-29 days at 4,850 to 7,600 m altitude). Arriving at 4,850 m an initial increase of Hb and Hct was followed by a short decrease during the first week and a continuous increase during the further stay.
  
  
  RESULTS
  In maximum, 131.3% (Hb) and 117.4% (Hct) of the starting point were reached during the fourth week at altitude after the attempt to reach the summit of Broad Peak (8,047 m). Parallel the dehydration in the beginning turned to a hyperhydration at the end of the stay (D(2)O method).
  
  
  CONCLUSIONS
  Erythropoietin rose only temporarily at altitude (max. +11 +1 mU/ml serum). Upon return, Hb and Hct normalized within a few days whereas hemoglobin mass (initially 881+ 44 g, CO-Hb method) was still increased by 13% (p < 0.01).
  
  
  CONCLUSIONS
  In conclusion, a hemoconcentration effect (dehydration) is the reason of the initial peak of Hb and Hct. The further increase can only partially be explained by an absolute increase of Hb and Hct caused by stimulated erythropoiesis. A shift of intravasal fluid to the interstitial space is the other main reason of the observed changes in red blood count.
authors.affiliation: Department of Visceral and Thoracic Surgery, Armed Forces Hospital Ulm, Ulm, Germany. markus.tannheimer@arcor.de
authors.forename: Markus
authors.initials: M
authors.lastname: Tannheimer
authors.forename: Christian
authors.initials: C
authors.lastname: Fusch
authors.forename: Dieter
authors.initials: D
authors.lastname: Böning
authors.forename: Alfred
authors.initials: A
authors.lastname: Thomas
authors.forename: Michael
authors.initials: M
authors.lastname: Engelhardt
authors.forename: Roland
authors.initials: R
authors.lastname: Schmidt
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000532:Altitude Sickness / Q000503:physiopathology* / Q000517:prevention & control; D001823:Body Composition / Q000502:physiology; D001834:Body Water / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D003081:Cold Climate; D004906:Erythrocyte Count; D004921:Erythropoietin / Q000097:blood; D005260:Female; D006400:Hematocrit; D006452:Hemoglobinometry; D006801:Humans; D008297:Male; D009051:Mountaineering / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D012016:Reference Values; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D004921:Erythropoietin; D010100:Oxygen