title: Defining metabolic acidosis in patients with septic shock using Stewart approach.
abstract: OBJECTIVE
  The aim of this study was to define the nature of metabolic acidosis in patients with septic shock on admission to intensive care unit (ICU) using Stewart method. We also aimed to compare the ability of standard base excess (SBE), anion gap (AG), and corrected AG for albumin and lactate (AGcorr) to accurately predict the presence of unmeasured anions (UA).
  
  
  METHODS
  Thirty consecutive patients with septic shock were prospectively included on ICU admission. Stewart equations modified by Figge were used to calculate the strong ion difference and the strong ion gap (SIG).
  
  
  RESULTS
  Most patients had multiple underlying mechanisms explaining the metabolic acidosis. Unmeasured anions and hyperchloremia were present in 70% of the patients. Increased UA were present in 23% of patients with normal values of SBE and [HCO3-]. In these patients, plasma [Cl-] was significantly lower compared with patients with low SBE and increased UA (103 [102-106.6] vs 108 [106-111] mmol/L; P=.01, respectively). Corrected AG for albumin and lactate had the best correlation with SIG (r²=0.94; P<.0001) with good agreement (bias, 0, and precision, 1.22) and highest area under the receiver operating characteristic curve (0.995; 95% confidence interval, 0.87-1) to discriminate SIG acidosis.
  
  
  CONCLUSIONS
  Patients with septic shock exhibit a complex metabolic acidosis at ICU admission. High UA may be present with normal values of SBE and [HCO3-] as a result of associated "relative" hypochloremic alkalosis. Corrected AG for albumin and lactate offers the most accurate bedside alternative to Stewart calculation of UA.
authors.affiliation: Service de Réanimation Polyvalente, Centre Hospitalier Dr Schaffner de Lens, 62307 Lens Cedex, France. jihad_mallat@msn.com
authors.forename: Jihad
authors.initials: J
authors.lastname: Mallat
authors.forename: Damien
authors.initials: D
authors.lastname: Michel
authors.forename: Pascale
authors.initials: P
authors.lastname: Salaun
authors.forename: Didier
authors.initials: D
authors.lastname: Thevenin
authors.forename: Laurent
authors.initials: L
authors.lastname: Tronchon
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D000368:Aged; D000838:Anions / Q000097:blood; D001784:Blood Gas Analysis; D002712:Chlorides / Q000097:blood; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D019344:Lactic Acid / Q000097:blood*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012709:Serum Albumin / Q000032:analysis*; D012772:Shock, Septic / Q000097:blood / Q000150:complications*
chemical_list: D000838:Anions; D002712:Chlorides; D012709:Serum Albumin; D019344:Lactic Acid