title: Higher venous bicarbonate concentration associated with hypoxemia, not acute mountain sickness, after ascent to moderate altitude.
abstract: BACKGROUND
  The pathophysiology underlying acute mountain sickness (AMS) and excessive hypoxemia at high altitudes is not fully understood. Previous work by our group has demonstrated a significant association between urinary measures of dehydration and bicarbonate retention in subjects developing excessive hypoxemia and AMS at high altitudes. To further characterize these findings, we returned to our original testing site to examine the hypothesis that subjects with lower levels of oxygen saturation and/or AMS would possess higher levels of venous bicarbonate.
  
  
  METHODS
  Medical history inquiry, clinical examination, Lake Louise scoring, and the collection of venous levels of bicarbonate concentration and base excess were performed on 52 lowland-dwelling persons after they completed a religious pilgrimage in the Nepal Himalayas to approximately 4,250 m.
  
  
  RESULTS
  Oxygen saturation levels were strongly and inversely correlated with serum levels of venous bicarbonate and base excess, whereas AMS and Lake Louise scores were not associated with these measures of alkalosis.
  
  
  CONCLUSIONS
  Our data suggest an association between measures of serum bicarbonate anion retention and decreasing oxygen saturation. Our data do not demonstrate an association between AMS or Lake Louise scores and measures of serum bicarbonate level. We propose that excessive hypoxemia at high altitudes may be associated with a compromised ability of the kidney to metabolically compensate for an altitude-induced hypocapnic alkalosis.
authors.affiliation: The Johns Hopkins University/Sinai Hospital Program in Internal Medicine, Baltimore, MD, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Cumbo
authors.forename: Darren
authors.initials: D
authors.lastname: Braude
authors.forename: Buddha
authors.initials: B
authors.lastname: Basnyat
authors.forename: Lisa
authors.initials: L
authors.lastname: Rabinowitz
authors.forename: Andres G
authors.initials: AG
authors.lastname: Lescano
authors.forename: Mark B
authors.initials: MB
authors.lastname: Shah
authors.forename: Destin J
authors.initials: DJ
authors.lastname: Radder
authors.forename: Govind
authors.initials: G
authors.lastname: Bashyal
authors.forename: Steven R
authors.initials: SR
authors.lastname: Gambert
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood* / Q000503:physiopathology; D001639:Bicarbonates / Q000097:blood*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000503:physiopathology; D008297:Male; D009051:Mountaineering / Q000502:physiology*; D009390:Nepal
chemical_list: D001639:Bicarbonates