title: Lactic acid kinetics in respiratory alkalosis.
abstract: OBJECTIVE
  To evaluate the impact of respiratory alkalosis on the elimination of intravenously infused lactate.
  
  
  METHODS
  Prospective, randomized, crossover study.
  
  
  METHODS
  Medical ICU of a university hospital.
  
  
  METHODS
  Eight patients treated by ventilatory support for neurologic or neuromuscular diseases.
  
  
  METHODS
  Patients were investigated on two occasions: during normoventilation (pH 7.42 +/- 0.1, PCO2 41 +/- 2 torr [5.5 +/- 0.2 kPa]) and during respiratory alkalosis (pH 7.59 +/- 0.1, PCO2 27 +/- 2 torr [3.6 +/- 0.2 kPa]) induced by controlled hyperventilation. To evaluate lactate elimination kinetics, 1 mmol/kg body weight of L-lactic acid was infused over 5 mins.
  
  
  RESULTS
  Arterial lactate concentrations and blood gas values were determined before and repeatedly after the infusion. Lactate elimination variables were calculated from the plasma curve by using a two-compartment model. Respiratory alkalosis increased plasma lactate from 1.56 +/- 0.1 to 2.49 +/- 0.2 mmol/L (p less than .001). The lactate elimination half-life increased from 4.57 +/- 0.2 mins at pH 7.42, to 9.96 +/- 1.1 mins during pH 7.59 (p less than .01), and beta half-life increased from 12.2 +/- 1.9 to 44.1 +/- 1 mins (p less than .01). Whole-body clearance decreased 40% from 24.2 +/- 2.9 to 14.3 +/- 2.0 mL/kg body weight-min (p less than .01).
  
  
  CONCLUSIONS
  Respiratory alkalosis increases the basal concentration of plasma lactate and decreases clearance of infused lactic acid. These findings provide further evidence of the adverse effects of alkalosis.
authors.affiliation: 1st Department of Medicine, University of Vienna, Austria.
authors.forename: W
authors.initials: W
authors.lastname: Druml
authors.forename: G
authors.initials: G
authors.lastname: Grimm
authors.forename: A N
authors.initials: AN
authors.lastname: Laggner
authors.forename: K
authors.initials: K
authors.lastname: Lenz
authors.forename: B
authors.initials: B
authors.lastname: Schneeweiss
mesh_terms: D000368:Aged; D000472:Alkalosis, Respiratory / Q000097:blood* / Q000628:therapy; D005260:Female; D006207:Half-Life; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000097:blood; D007262:Infusions, Intravenous; D007773:Lactates / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019344:Lactic Acid; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial; D013997:Time Factors
chemical_list: D007773:Lactates; D019344:Lactic Acid