COMPARISON OF TWO DIFFERENT MODALITIES OF BICARBONATE FOR DETERMINATION OF ANION GAP IN CRITICALLY ILL PATIENTS

Main Article Content

Sheryar Orakzai
Munir Hussain
Aamir Ijaz
Sidra Sadiq
Mirza Muhammad Dawood
Jehan Zeb

Abstract

OBJECTIVE: To compare anion gap estimated through measured and calculated bicarbonate modalities to be used interchangeably in critically ill metabolic acidosis patients.


METHODS: This cross-sectional study was conducted at Rehman Medical Institute, Peshawar, Pakistan from September 2019 to March 2020.  Out of 390 critically ill patients, 200 cases of metabolic acidosis were selected by non-probability consecutive sampling technique. Measured and calculated bicarbonate values were obtained through Cobas-c 501© (Roche) using enzymatic method and Cobas-b 221© (Roche) blood gas analyzer respectively. Statistical analysis was done by using SPSS-23.


RESULTS: Normal anion gap metabolic acidosis (NAG-MA) and high anion gap metabolic acidosis (HAG-MA) based on calculated bicarbonate levels was observed in 57 (28.5%) and 143 (71.5%) cases as compared to 55 (27.5%) and 145 (72.5%) cases based on measured bicarbonate levels respectively (p>0.45). A significant correlation (r=0.888 and 0.656, r2=0.788 and 0.431) (p<.001) was found between mean values of NAG-MA and HAG-MA respectively, when each was calculated through both modalities of bicarbonate. On applying Bland Altman plot, bias was 1.45±2.89 and -2.14±3.87mmol/L, Upper limit of agreement (LOA) was 7.13 and 5.46 for NAG-MA and HAG-MA, while lower LOA was -4.23 and -9.74 for NAG-MA and HAG-MA respectively. According to the model Bland Altman plot and Story & Postuie criteria, bias and the levels of agreement were not appropriate to conclude that both entities of anion gap could be used interchangeably. 


CONCLUSION: Normal and high anion gap metabolic acidosis estimated by measured and calculated bicarbonate cannot be used interchangeably in critically ill patients.

Article Details

How to Cite
Orakzai, S., M. Hussain, A. Ijaz, S. Sadiq, M. Dawood, and J. Zeb. “COMPARISON OF TWO DIFFERENT MODALITIES OF BICARBONATE FOR DETERMINATION OF ANION GAP IN CRITICALLY ILL PATIENTS”. KHYBER MEDICAL UNIVERSITY JOURNAL, Vol. 14, no. 1, Mar. 2022, doi:10.35845/kmuj.2022.21613.
Section
Original Articles

References

1. Ho KM, Lan NS, Williams TA, Harahsheh Y, Chapman AR, Dobb GJ, et al. A comparison of prognostic significance of strong ion gap (SIG) with other acid-base markers in the critically ill: a cohort study. J Intensive Care 2016;4:43. https://doi.org/10.1186/s40560-016-0166-z.
2. Borron SW. Acid–Base Balance in the Poisoned Patient. In: Brent J, Burkhart K, Dargan P, Hatten B, Megarbane B, Palmer R, et al., Editors. Critical Care Toxicology: Diagnosis and Management of the Critically Poisoned Patient. Cham: Springer International Publishing; 2017. p. 325-58. https://doi.org/10.1007/978-3-319-17900-1_67.
3. Hamilton PK, Morgan NA, Connolly GM, Maxwell AP. Understanding Acid-Base Disorders. Ulster Med J 2017;86(3):161-6.
4. Samuel R. A Graphical Tool for Arterial Blood Gas Interpretation using Standard Bicarbonate and Base Excess. Indian J Med Biochem 2018;22(1):85-9. https://doi.org/10.5005/jp-journals-10054-0061.
5. Bishop M. Clinical Correlations and Analytical Procedures. In: Fody EP, Scheoff LE, Editors. Clinical chemistry: principles, techniques, and correlations. 8th Ed. Philadelphia : Wolters Kluwer; 2017. p. 931-2.
6. Raibman Spector S, Mayan H, Loebstein R, Markovits N, Priel E, Massalha E, et al. Pyroglutamic acidosis as a cause for high anion gap metabolic acidosis: a prospective study. Sci Rep 2019;9(1):3554. https://doi.org/10.1038/s41598-019-39257-4.
7. Rudkin SE, Grogan TR, Treger RM. The Bicarbonate Ratio in Early Lactic Acidosis: Time for Another Delta? J Kidney 360 2021;2(1):20-5. https://doi.org/10.34067/KID.0000842019.
8. Ijaz A. Acid Base Disorders. In: Ikram A, Siddiq A, Tariq A, Hussain A, Ali A, Majeed A, et al., Editors. Chemical Pathology for the Beginners. 1st Ed. 22-Urdu Bazar, Lahore: Azeem Academy Publishers; 2018. p. 85-6.
9. Reijenga J, van Hoof A, van Loon A, Teunissen B. Development of Methods for the Determination of pKa Values. Anal Chem Insights 2013;8:53-71. https://doi.org/10.4137/ACI.S12304.
10. Rifai N, Horvath A, Rita , Wittwer C, T. Electrolytes and Blood Gases. In: Schindler EI, Brown SM, Scott MG, editors. Tietz textbook of Clinical Chemistry and Molecular Diagnostics. 6th Ed: St. Louis, Missouri: Elsevier Publishers; 2018. p. 617-8.
11. Ing TS, Massie L, Tzamaloukas AH, Lew SQ. Plasma bicarbonate and total carbon dioxide: terms to be employed with precision. Int Urol Nephrol 2021;53(7):1483-4. https://doi.org/10.1007/s11255-020-02734-1.
12. Chen H-Z, Liang W-S, Yao W-F, Liu T-X. Compression methods after femoral artery puncture: A protocol for systematic review and network meta-analysis. Medicine (Baltimore) 2021;100(4):e24506-e. https://doi.org/10.1097/MD.0000000000024506.
13. Bijapur MB, Kudligi NA, Asma S. Central Venous Blood Gas Analysis: An Alternative to Arterial Blood Gas Analysis for pH, PCO(2), Bicarbonate, Sodium, Potassium and Chloride in the Intensive Care Unit Patients. Indian J Crit Care Med 2019;23(6):258-62. https://doi.org/10.5005/jp-journals-10071-23176.
14. Chittamma A, Vanavanan S. Comparative study of calculated and measured total carbon dioxide. Clin Chem Lab Med 2008;46(1):15-7. https://doi.org/10.1515/cclm.2008.005.
15. Kumar V, Karon BS. Comparison of measured and calculated bicarbonate values. Clin Chem 2008;54(9):1586-7. https://doi.org/10.1373/clinchem.2008.107441.
16. Story DA, Poustie S. Agreement between two plasma bicarbonate assays in critically ill patients. Anaesth Intensive Care Med 2000;28(4):399-402. https://doi.org/10.1177/0310057X0002800407.
17. Goundan PN, Willard DL, Sahin-Efe A, Fan S-LL, Alexanian SM. Comparison of bicarbonate values from venous blood gas and chemistry panels measured at the time of diagnosis and resolution of diabetes ketoacidosis. J Clin Transl Endocrinol 2019;18:100205. https://doi.org/10.1016/j.jcte.2019.100205.
18. Kim Y, Massie L, Murata GH, Tzamaloukas AH. Discrepancy between Measured Serum Total Carbon Dioxide Content and Bicarbonate Concentration Calculated from Arterial Blood Gases. Cureus 2015;7(12):e398-e. https://doi.org/10.7759/cureus.398.
19. Chandrasekaran S, Gopinath P. Evaluation of pKa as a cause of discordance between calculated and measured bicarbonate in arterial and venous blood. Int Arch Integrated Med 2019;6(3):127-31.
20. Fujii T, Udy AA, Nichol A, Bellomo R, Deane AM, El-Khawas K, et al. Incidence and management of metabolic acidosis with sodium bicarbonate in the ICU: An international observational study. J Crit Care 2021;25(1):1-10. https://doi.org/10.1186/s13054-020-03431-2.
21. Roche Diagnostics. CO2-L Bicarbonate Liquid. 2020 [Accessed On: January 11, 2022]. Available from URL: https://pim-eservices.roche.com/eLD/api/downloads/2959b7e5-c101-e911-edbb-00215a9b3428?countryIsoCode=pk
22. Harr KE, Flatland B, Nabity M, Freeman KP. ASVCP guidelines: allowable total error guidelines for biochemistry. Vet Clin Pathol 2013;42(4):424-36. https://doi.org/10.1111/vcp.12101.
23. Gerke O. Reporting Standards for a Bland-Altman Agreement Analysis: A Review of Methodological Reviews. Diagnostics (Basel) 2020;10(5):334. https://doi.org/10.3390/diagnostics10050334.
24. Sadler WA. Using the variance function to generalize Bland-Altman analysis. Ann Clin Biochem 2019;56(2):198-203. https://doi.org/10.1177/0004563218806560.
25. Nasir NM, Sthaneshwar P, Yunus PJ, Yap SF. Comparing measured total carbon dioxide and calculated bicarbonate. Malays J Pathol 2010;32(1):21-6.
26. Mohan T, Kumar BV. Comparison of measured Serum Total Carbon Dioxide with calculated Bicarbonate calculated from Arterial Blood Gas Analysis. J Med Biochem 2017;21(2):76-80.
27. Stöckl D, Rodríguez Cabaleiro D, Van Uytfanghe K, Thienpont LM. Interpreting method comparison studies by use of the bland-altman plot: reflecting the importance of sample size by incorporating confidence limits and predefined error limits in the graphic. Clin Chem 2004;50(11):2216-8. https://doi.org/10.1373/clinchem.2004.036095.
28. Kumar A, Kushwah S, Sahay S. Effect of extra amount of heparin in syringe and its effect on arterial blood gas analysis. Eur J Pharm Med Res 2015;2(6):290-3.
29. Stein H. Spuriously Low Serum Bicarbonate Levels in Patients With Hyperlipidemia: A Report of 4 Cases. Am J Kidney Dis 2019;73(1):131-3. https://doi.org/10.1053/j.ajkd.2018.04.016.