Alkalinizing effects of oral sodium bicarbonate and sodium acetate in sedentary horses

Equimolar solutions of sodium bicarbonate (NaHCO₃) or sodium acetate (NaC₂H₃O₂), or deionised water (as a negative control) were administered by nasogastric intubation randomly to each of 12 sedentary mares every 2 weeks. Anaerobic samples of jugular venous blood were obtained hourly until 7 h after administration and were analysed for pH, pCO₂, and concentrations of tCO₂, HCO₃^-, Na⁺, K⁺, Cl^-, and Ca⁺⁺. Measured strong ion difference (SID_m), anion gap (AG), and estimated strong ion gap (SIG_est) were calculated. Least square means differences for each variable were determined using ANOVA for repeated measures. Significance level was set at P < 0.05. Treatment with NaHCO₃ increased pH, pCO₂, [tCO₂], [HCO₃^-], [Na⁺], and SID_m within 1 h of intubation (P < 0.05). Peaks were reached at 2 (pH and [Na⁺]) and 3 h (pH, pCO₂, [tCO₂], [HCO₃^-], and SID_m) after NaHCO₃ treatment. Sodium acetate increased [Na⁺] within 1 h of intubation; pH, [tCO₂], and [HCO₃^-] within 2 h; and pCO₂ and SID_m within 3 h (P < 0 .05). Peaks in pCO₂, [tCO₂], and [HCO₃^-] (4 h) and in pH and SID_m (5 h) were later with NaC₂H₃O₂ when compared with NaHCO₃. Changes in AG, SID_m, and SIGest were delayed after NaC₂H₃O₂ treatment, corresponding to the lags in venous pH, pCO₂, [tCO₂], and [HCO₃^-]. Serum [K⁺] decreased from 3 through 6 h for both treatments when compared to H₂O control (P < 0 .05). Serum [Cl^-] was decreased only for NaHCO₃ at 3 h (P < 0.05). Serum [Ca⁺⁺] was decreased for NaHCO₃ at 2, 3, 4, and 7 h and for NaC₂H₃O₂ only at 3 h (P < 0 .05). It was concluded that oral NaC₂H₃O₂ in horses caused a metabolic alkalosis similar to that caused by oral NaHCO₃, but that the peaks in pH, pCO₂, [tCO₂], [HCO₃^-], SID_m, AG, and SIG_est were delayed after NaC2H3O2 treatment.