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

Abstract

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 (SIDm), anion gap (AG), and estimated strong ion gap (SIGest) 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 NaHCO3increased pH, pCO2, [tCO2], [HCO3−], [Na+], and SIDm within 1 h of intubation (P<0.05). Peaks were reached at 2 (pH and [Na+]) and 3 h (pH, pCO2, [tCO2], [HCO3−], and SIDm) after NaHCO3 treatment. Sodium acetate increased [Na+] within 1 h of intubation; pH, [tCO2], and [HCO3−] within 2 h; and pCO2 and SIDm within 3 h (P<0.05). Peaks in pCO2, [tCO2], and [HCO3−] (4 h) and in pH and SIDm (5 h) were later with NaC2H3O2 when compared with NaHCO3. Changes in AG, SIDm, 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 NaC2H3O2in horses caused a metabolic alkalosis similar to that caused by oral NaHCO3, but that the peaks in pH, pCO2, [tCO2], [HCO3−], SIDm, AG, and SIGest were delayed after NaC2H3O2 treatment.