title: Severe hyperlactatemia with normal base excess: a quantitative analysis using conventional and Stewart approaches.
abstract: BACKGROUND
  Critically ill patients might present complex acid-base disorders, even when the pH, PCO2, [HCO3-], and base excess ([BE]) levels are normal. Our hypothesis was that the acidifying effect of severe hyperlactatemia is frequently masked by alkalinizing processes that normalize the [BE]. The goal of the present study was therefore to quantify these disorders using both Stewart and conventional approaches.
  
  
  METHODS
  A total of 1,592 consecutive patients were prospectively evaluated on intensive care unit admission. Patients with severe hyperlactatemia (lactate level > or = 4.0 mmol/l) were grouped according to low or normal [BE] values (<-3 mmol/l or >-3 mmol/l).
  
  
  RESULTS
  Severe hyperlactatemia was present in 168 of the patients (11%). One hundred and thirty-four (80%) patients had low [BE] levels while 34 (20%) patients did not. Shock was more frequently present in the low [BE] group (46% versus 24%, P = 0.02) and chronic obstructive pulmonary disease in the normal [BE] group (38% versus 4%, P < 0.0001). Levels of lactate were slightly higher in patients with low [BE] (6.4 +/- 2.4 mmol/l versus 5.6 +/- 2.1 mmol/l, P = 0.08). According to our study design, the pH, [HCO3-], and strong-ion difference values were lower in patients with low [BE]. Patients with normal [BE] had lower plasma [Cl-] (100 +/- 6 mmol/l versus 107 +/- 5 mmol/l, P < 0.0001) and higher differences between the changes in anion gap and [HCO3-] (5 +/- 6 mmol/l versus 1 +/- 4 mmol/l, P < 0.0001).
  
  
  CONCLUSIONS
  Critically ill patients may present severe hyperlactatemia with normal values of pH, [HCO3-], and [BE] as a result of associated hypochloremic alkalosis.
authors.affiliation: Servicio de Terapia Intensiva, Sanatorio Otamendi y Miroli, Buenos Aires, Argentina.
authors.forename: Graciela
authors.initials: G
authors.lastname: Tuhay
authors.forename: María Carolina
authors.initials: MC
authors.lastname: Pein
authors.forename: Fabio Daniel
authors.initials: FD
authors.lastname: Masevicius
authors.forename: Daniela Olmos
authors.initials: DO
authors.lastname: Kutscherauer
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Dubin
mesh_terms: D000136:Acid-Base Equilibrium; D000140:Acidosis, Lactic / Q000097:blood*; D000368:Aged; D001639:Bicarbonates / Q000097:blood; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D002712:Chlorides / Q000097:blood; D016638:Critical Illness; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007362:Intensive Care Units; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood; D012769:Shock / Q000097:blood
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D002245:Carbon Dioxide; D019344:Lactic Acid