Background: The analysis of arterial blood gas (ABG) is an invasive procedure that is used frequently in the emergency department (ED) to evaluate the acid-base status of critically-ill patients. However, capnometry is an alternative procedure that has been used in recent years to determine the metabolic status of patients’ blood. Considering the correlation between end-tidal carbon dioxide (ETCO2) and arterial partial pressure of carbon dioxide (PaCO2) identified in the previous studies and the strong correlation between PaCO2 and bicarbonate (HCO3-), we assumed that ETCO2 might be a useful parameter in predicting the presence of metabolic acidosis. The aim of this study was to determine the correlation between ETCO2 and the parameters of ABG in adult patients who were likely present metabolic acid-base disturbances in the Emergency Department of Imam Reza Hospital, the largest academic hospital in Mashhad in northeast Iran.Methods: This was a cross-sectional study conducted during six months on 62 adult patients who presented with suspected metabolic acid-base disorders to the ED. The exclusion criteria were patients with chronic obstructive pulmonary diseases, loss of consciousness, intubated patients, and those who were unable to tolerate capnography. The patients’ demographic information and vital signs were recorded. Also, ABG and ETCO2 results were recorded. The Pearson product moment correlation analysis and linear regression were used to determine the correlation between ETCO2 and ABG parameters.Results: Sixty-four patients were enrolled, consisting of 37 men and 27 women with a mean age of 55.4 ± 22.7 years. The most common complaints presented were nausea and vomiting (n = 24). The average value for ETCO2 was 26.2 ± 6.1. There were significant linear correlations between ETCO2 level, pH (r = 0.368), HCO3 - (r = 0.869), PaCO2 (r = 0.795), and Base Excess (B.E.) (r = 0.346). HCO3 and PaCO2 were the significant predictor values for ETCO2 (linear regression analysis).Conclusion: ETCO2 can be an appropriate indicator to estimate HCO3- and PaCO2 in critical emergency situations, but it cannot be used as an indicator to estimate all ABG variables.

The present paper firstly announces the possibility of using a Schiff base as an acid-base indicator. This surprising phenomenon can be considered as an interest due to the fact that Schiff bases are usually unstable in solutions and definitely undergo hydrolysis. It was found that such a specific observation depends merely upon the chemical structure and type of the substitute of amine that reacts with aldehyde to give the Schiff base. The latter reagent 4[(4-dimethylamino-benzylidene)-amino]-benzene sulfonamide was synthesized from the condensation of sulfanilamide with p-dimethylaminobenzaldehyde. The reagent solution shows a reproducible change in its color due to the addition of acid and base. A UV-Vis spectroscopic characterization and acid-base equilibrium study of the reagent for its possible use as an indicator were investigated. The results show that the reagent is an amphoteric which possesses four ionization constants Ka1, Ka2, Kb1 and Kb2 of weak dibasic and diacidic properties. The value of pKa2 (9.80) is parallel to the observed transition interval pH 9.5 (yellow) and pH 10.5 (colorless), which is considered to be the indicator exponents pKi. It was concluded that the benzyl sulfonamide group plays a key role in the stability of the reagent towards hydrolysis and also for indicator characteristics through breaking the conjugation.

Objectives: We aimed to determine the parameters of acid-base balance in patients with chronic renal failure (CRF) and the relationship between the parameters evaluating acid-base balance and creatinine clearance. Methods: The current cross-sectional study was conducted on 300 patients with CRF (180 males and 120 females). Clinical examination and blood tests by taking an arterial blood sample for blood gas measurement as well as venous blood for biochemical tests to select study participants were performed. Results: Patients with CRF in the metabolic acidosis group accounted for 74%, other types of disorders were less common. The average pH, PCO2, HCO3, tCO2 and BE of the patient group were 7. 35 0. 09, 34. 28 6. 92 mmHg, 20. 18 6. 06 mmol/L, 21. 47 6. 48 mmHg and-4. 72 6. 61 mmol/L respectively. These parameters are lower than normal values and decrease by progressing chronic kidney disease (CKD) stage. These parameters correlated moderately with creatinine clearance. Conclusions: In patients with CRF, metabolic acidosis is predominant, and acid-base balance parameters are positively correlated with creatinine clearance.