DETERMINANTS AND UTILITY OF THE ANION GAP IN PREDICTING HYPERLACTATEMIA IN CATTLE

The objectives of this study were to investigate the determinants of t he anion gap (AG) in cattle and to evaluate the utility of AG in detec ting hyperlactatemia in sick neonatal calves and adult cattle. The AG was calculated as AG = ([Na+] + [K+]) - ([Cl-] + [HCO3-]), with all va lues in mEq/L. The AG of healthy neonatal calves (n = 16) was 29.6 +/- 6.2 mEq/L (mean +/- SD), and the blood L-lactate concentration ranged from 0.5 to 1.2 mM/L. The AG was significantly (P <.05) correlated wi th serum phosphate (r =.66) and creatinine (r =.51) concentrations. Th e AG of neonatal calves with experimentally induced diarrhea (n = 16) was 28.6 +/- 5.6 mEq/L, and the blood L-lactate concentration ranged f rom 1.1 to 2.9 mM/L, The AG was significantly correlated with blood L- lactate concentration (r =.67), serum phosphate concentration (r =.63) , creatinine concentration (r =.76), and blood pH (r = -.61). The AG o f adult cattle with abomasal volvulus (n = 41) was 20.5 +/- 7.8 mEq/L, and the blood L-lactate concentration ranged from 0.6 to 15.6 mM/L. T he AG was significantly correlated with blood l.-lactate concentration (r =.60), serum phosphate concentration (r =.71), creatinine concentr ation (r =.65), albumin concentration (r =.47), total protein concentr ation (r =.54), blood pyruvate concentration (r =.67), and blood pH (r =-.41) but not plasma P-OH butyrate concentration. The results indica te that the AG in cattle is only moderately correlated with blood L-la ctate concentration and is similarly correlated with serum phosphate a nd creatinine concentrations in neonatal calves and adult cattle, as w ell as with serum albumin and total protein concentrations in adult ca ttle. Anion gap determination is of limited usefulness in predicting b rood L-lactate concentration in sick cattle, whereas the correlation b etween AG and serum creatinine concentration in sick cattle suggests t hat an increased AG should alert the clinician to the potential presen ce of uremic anions.