Abstract
Introduction: The evaluation of metabolism and the diagnostic classification of acid-base disorders has generated great controversy. Acid-base balance (ABB) is approached by means of the physicochemical and Henderson’s models.Objective: To compare two diagnostic approaches to ABB in patients with severe sepsis.Materials and methods: Prospective, descriptive study conducted in patients with severe sepsis. ABB was analyzed within the first 24 hours. The diagnosis was compared according to each model and the causes of the disorders were compared according to the physicochemical model.Results: 38 patients were included in the study, of which 21 (55%) were women; the mean age was 49 years, the median APACHE II, 13.28, and the mortality at 28 days, 24.3%. The traditional approach identified 8 patients with normal ABB, 20 with metabolic acidosis, and 10 with other disorders. Based on the physicochemical model, all subjects had acidosis and metabolic alkalosis. Increased strong ion difference (SID) was the most frequently observed disorder.Conclusion: The physicochemical model was useful to diagnose more patients with acid-base disorders. According to these results, all cases presented with acidosis and metabolic alkalosis; the most frequent proposed mechanism of acidosis was elevated SID. The nature of these disorders and their clinical relevance is yet to be established.
Highlights
The evaluation of metabolism and the diagnostic classification of acid-base disorders has generated great controversy
In the 1960’s this approach was extended with the concept of excess base (EB), which sought to quantify the metabolic component and develop curves that correlated pCO2, HCO3 and pH; the so-called practical approximations or “thumb” standards that are used to classify acid-base disorders derive from said curves. [4,5,6,7] At present, this proposal is known as the “classical” or “traditional” approach to understanding acid-base physiology; it analyzes Acid-base balance (ABB) based on different variables, the most important being bicarbonate and carbon dioxide (CO2)
Patients with metabolic acidosis are classified into the normal anion gap (AG) or high AG category, leading the clinician to suspect some specific causes of the acidosis
Summary
The evaluation of metabolism and the diagnostic classification of acid-base disorders has generated great controversy. Acid-base balance (ABB) is approached by means of the physicochemical and Henderson’s models. Acid-base balance (ABB) in blood has been under permanent study since Lawrence J. Henderson first presented this approach in 1908. The other model proposed for acid-base analysis was presented in the 1970s by Peter Stewart: the so-called physicochemical approach. It states that pH is determined by three independent variables: strong ion difference (SID), total weak non-volatile acids (ATOT) and partial pressure of carbon dioxide (pCO2). [7,9] Currently, concepts such as effective SID, strong ion gap (SIG), base excess contributed by unmeasured anions (BEua), and corrected AG have emerged as an extension of this model, and together are sometimes called “semiquantitative” approach. It states that pH is determined by three independent variables: strong ion difference (SID), total weak non-volatile acids (ATOT) and partial pressure of carbon dioxide (pCO2). [7,9] Currently, concepts such as effective SID, strong ion gap (SIG), base excess contributed by unmeasured anions (BEua), and corrected AG have emerged as an extension of this model, and together are sometimes called “semiquantitative” approach. [6,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
