The Henderson-Hasselbalch equation and the base excess have been used traditionally to describe the acid-base balance of the blood. In 1981, Stewart proposed a new model of acid-base balance based upon three variables, the "strong ion difference" (SID), the total weak acids (ATot), and the partial pressure of carbon dioxide (Pco2). Over 20 years later, Stewart's physiochemical model still remai...

IDEALLY, THE EVALUATION of acid-base balance should be made from the determination of 002 content and pH on arterial plasma. Obtaining arterial blood is not, however, a routine clinical procedure. Hence, next in order of preference is the performance of these two determinations on plasma of arterialized blood which may be easily obtained by soaking the arm of the subject in a water bath at 40#{...

Sir,—In the Correspondence section of the Journal (1972, 44, 233) Dr Marx mentioned that foetal acid-base values obtained from umbilical artery blood at Caesarean sections did not correlate with the condition of the newborn infant at birth. I should like to provide evidence that acid-base values of umbilical artery blood are not reliable at Caesarean sections under general anaesthesia. We measu...