title: Physicochemical interpretation of acid-base abnormalities in 54 adult horses with acute severe colitis and diarrhea.
abstract: BACKGROUND
  The quantitative effect of strong electrolytes, pCO2 , and plasma protein concentration in determining plasma pH and bicarbonate concentrations can be demonstrated with the physicochemical approach. Plasma anion gap (AG) and strong ion gap (SIG) are used to assess the presence or absence of unmeasured anions.
  
  
  OBJECTIVE
  The physicochemical approach is useful for detection and explanation of acid-base disorders in horses with colitis. AG and SIG accurately predict hyperlactatemia in horses with colitis.
  
  
  METHODS
  Fifty-four horses with acute colitis and diarrhea.
  
  
  METHODS
  Retrospective study. Physicochemical variables were calculated for each patient. ROC curves were generated to analyze sensitivity and specificity of AG and SIG for predicting hyperlactatemia.
  
  
  RESULTS
  Physicochemical interpretation of acid-base events indicated that strong ion metabolic acidosis was present in 39 (72%) horses. Mixed strong ion acidosis and decreased weak acid (hypoproteinemia) alkalosis was concomitantly present in 17 (30%) patients. The sensitivity and specificity of AG and SIG to predict hyperlactatemia (L-lactate > 5 mEq/L) were 100% (95% CI, 66.4-100; P < .0001) and 84.4% (95% CI, 70.5-93.5 P < .0001). Area under the ROC curve for AG and SIG for predicting hyperlactatemia was 0.95 (95% CI, 0.86-0.99) and 0.93 (95% CI, 0.83-0.99), respectively.
  
  
  CONCLUSIONS
  These results emphasize the importance of strong ions and proteins in the maintenance of the acid-base equilibria. AG and SIG were considered good predictors of clinically relevant hyperlactatemia.
authors.affiliation: Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada. dgomez@upei.ca
authors.forename: D E
authors.initials: DE
authors.lastname: Gomez
authors.forename: L G
authors.initials: LG
authors.lastname: Arroyo
authors.forename: H R
authors.initials: HR
authors.lastname: Stämpfli
authors.forename: L E
authors.initials: LE
authors.lastname: Cruz
authors.forename: O J
authors.initials: OJ
authors.lastname: Oliver
mesh_terms: D000136:Acid-Base Equilibrium; D000137:Acid-Base Imbalance / Q000662:veterinary*; D000818:Animals; D003092:Colitis / Q000097:blood / Q000662:veterinary*; D003967:Diarrhea / Q000097:blood / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000097:blood*; D006736:Horses; D008297:Male; D014882:Water-Electrolyte Balance