Physical-chemical approach to acid-base alterations in the urine of sheep with hypochloremic alkalosis

Abstract

The physical-chemical approach to determine urinary pH is relatively new and has not yet been used in pathological conditions in animals. The main objective of this paper was to demonstrate the validity of this theory in the urine of sheep with hypochloremic metabolic alkalosis. An experimental-type study was conducted to induce hypochloremic metabolic alkalosis in sheep. During the control and induction periods, calculated pH, measured pH, net acid excretion, ammonium and strong ion difference (SID) in urine were examined every 24 hours until development of paradoxical aciduria or physical deterioration of subjects. Pearson’s correlation (r) was determined between measured and calculated pH based on SID in urine. A high correlation between measured and calculated urine pH was observed using SID calculated from net acid excretion (r = 0.874). The correlation between calculated SID and urine pH was significant (r = 0.839). However, the correlation between SID and measured urine pH was moderate (r = 0.588). It is concluded that there is a high correlation between pH calculated from SID using net acid excretion and pH measured in the urine of sheep with hypochloremic metabolic alkalosis. This indicates that urine pH depends strongly on SID and, therefore, a reduction in pH can be explained by a decrease in SID.