Utility of Stewart’s Acid-Base Approach in a Liver Intensive Care Unit: An Observational Study
,
Abstract
Background: Stewart's method of acid-base analysis involves analyzing the strong ion difference in the blood. The anion gap (AG), strong ion difference (SID), and strong ion gap (SIG) not only assist in diagnosing underlying acid-base disturbances but also serve as prognostic markers. This study aimed to analyze Stewart's approach in patients with cirrhosis.
Methods: Acid-base parameters of forty-eight cirrhosis patients requiring intensive care were prospectively studied. The primary objective of this study was to evaluate the prognostic value of SIG. The secondary objective was to examine the correlation between acid-base parameters, such as lactate, base excess of arterial blood gas analysis (ABG-BE), base excess of unmeasured anions [BE (UA)], AG, SID, and SIG.
Results: The median SIG was 4.1 (IQR: 2.5 - 5.6). The median albumin-corrected AG (acAG) level was 15 (IQR, 14–20). The median BE (UA) was -4.2 (IQR: -7.1, 1.7). Apparent SID and BE (UA) demonstrated a strong correlation (r = 0.92; p < 0.001). Effective SID was strongly correlated with ABG-BE (r = 0.83, p < 0.001). SIG and acAG showed a strong correlation with an r value of 0.94 (p < 0.001). An ICU stay of more than 8 days was considered prolonged (75th percentile). ABG-BE, SIG, and acAG on admission day effectively predicted prolonged ICU stay, with AUCs of 0.73, 0.75, and 0.78, respectively.
Conclusion: SIG effectively predicts prolonged ICU stay with good predictive ability. However, the anion gap, when corrected for albumin, is better than SIG in terms of predictive accuracy, requiring fewer variables and offering greater ease of use.
[2] Schwartz WB, Relman AS. A critique of the parameters used in the evaluation of acid-base disorders: whole-blood buffer base and standard bicarbonate compared with blood pH and plasma bicarbonate concentration. N Engl J Med. 1963; 268(25):1382-8.
[3] Stewart PA. Independent and dependent variables of acid-base control. Respir Physiol. 1978; 33(1):9-26.
[4] Kim MJ, Kim YH, Sol IS, Kim SY, Kim JD, Kim HY, et al. Serum anion gap at admission as a predictor of mortality in the pediatric intensive care unit. Sci Rep. 2017; 7(1):1456.
[5] Chen Q, Chen Q, Li L, Lin X, Chang SI, Li Y, et al. Serum anion gap on admission predicts intensive care unit mortality in patients with aortic aneurysm. Exp Ther Med. 2018; 16(3):1766-77.
[6] Dafal A, Kumar S, Agrawal S, Acharya S, Nirmal A. Admission anion gap metabolic acidosis and its impact on patients in medical intensive care unit. J Lab Physicians. 2021; 13(02):107-11.
[7] Paliwal R, Pakavakis A, Divatia JV, Kulkarni AP. Utility of Stewart's Approach to Diagnose Missed Complex Acid–Base Disorders as Compared to Bicarbonate-anion Gap-based Methodology in Critically Ill Patients: An Observational Study. Indian J Crit Care Med. 2022; 26(1):23.
[8] McPhail MJ, Shawcross DL, Abeles RD, Chang A, Patel V, Lee GH, et al. Increased survival for patients with cirrhosis and organ failure in liver intensive care and validation of the chronic liver failure–sequential organ failure scoring system. Clin Gastroenterol Hepatol. 2015; 13(7):1353-60.
[9] Fencl V, Jabor A, Kazda A, Figge J. Diagnosis of metabolic acid–base disturbances in critically ill patients. Am J Respir Crit Care Med. 2000; 162(6):2246-51.
[10] Stewart PA. Modern quantitative acid–base chemistry. Can J Physiol Pharmacol. 1983; 61(12):1444-61.
[11] John AK, Norbert L, Peter A, Rashad SB, Emmanuel AB, Stuart LG, et al. Kidney disease: Improving global outcomes (KDIGO) acute kidney injury work group. KDIGO clinical practice guideline for acute kidney injury. Kidney Int Suppl. 2012; 2:1-38.
[12] Singer M, Deutschman CS, Seymour CW, Shankar-Hari M, Annane D, Bauer M, et al. The third international consensus definitions for sepsis and septic shock (Sepsis-3). Jama. 2016; 315(8):801-10.
[13] Hopkins E, Sanvictores T, Sharma S. Physiology, Acid Base Balance. 2022 Sep 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–.
[14] Figge J, Jabor A, Kazda A, Fencl V. Anion gap and hypoalbuminemia. Crit Care Med. 1998; 26(11):1807-10.
[15] SIGGAARD-ANDERSEN O. The acid-base status of the blood. Scand J Clin Lab Invest Suppl. 1963; 15 Suppl 70:1-134.
[16] Berend K, de Vries AP, Gans RO. Physiological approach to assessment of acid-base disturbances. N Engl J Med. 2014; 371(20):1948.
[17] Grist G, Thomas D. Blood anion gaps and venoarterial carbon dioxide gradients as risk factors in long-term extracorporeal support. J Extra Corpor Technol. 1997; 29(1):6-10.
[18] Shackleton CR, Schechter MT, Bianco R, Hildebrand HD. Preoperative predictors of mortality risk in ruptured abdominal aortic aneurysm. J Vasc Surg. 1987; 6(6):583-9.
[19] Gunnerson KJ, Srisawat N, Kellum JA. Is there a difference between strong ion gap in healthy volunteers and intensive care unit patients? J Crit Care. 2010; 25(3):520-4.
[20] Rocktaeschel J, Morimatsu H, Uchino S, Bellomo R. Unmeasured anions in critically ill patients: can they predict mortality? Crit Care Med. 2003; 31(8):2131-6.
[21] Antonini B, Piva S, Paltenghi M, Candiani A, Latronico N. The early phase of critical illness is a progressive acidic state due to unmeasured anions. Eur J Anaesthesiol. 2008; 25(7):566-71.
[22] Dondorp AM, Chau TT, Phu NH, Mai NT, Loc PP, Chuong LV, et al. Unidentified acids of strong prognostic significance in severe malaria. Crit Care Med. 2004; 32(8):1683-8.
[23] Kaplan LJ, Kellum JA. Comparison of acid-base models for prediction of hospital mortality after trauma. Shock. 2008; 29(6):662-6.
[24] Durward A, Tibby SM, Skellett S, Austin C, Anderson D, Murdoch IA. The strong ion gap predicts mortality in children following cardiopulmonary bypass surgery. Pediatr Crit Care Med. 2005; 6(3):281-5.
[25] Murray D, Grant D, Murali N, Butt W. Unmeasured anions in children after cardiac surgery. J Thorac Cardiovasc Surg. 2007; 133(1):235-40.
[26] Drolz A, Horvatits T, Roedl K, Rutter K, Brunner R, Zauner C, et al. Acid-base status and its clinical implications in critically ill patients with cirrhosis, acute-on-chronic liver failure and without liver disease. Ann Intensive Care. 2018; 8(1):48.
[27] Cusack R, Rhodes A, Lochhead P, Jordan B, Perry S, Ball J, et al. The strong ion gap does not have prognostic value in critically ill patients in a mixed medical/surgical adult ICU. Intensive Care Med. 2002; 28(7):864-9.
[28] Zhou YH, Pang S, Miao GR, Zhao XY, Dong JZ. Combining the anion gap with the sequential organ failure assessment score to evaluate the short-term prognosis of patients in the cardiac intensive care unit. Int J Cardiol. 2023; 370:381-7.
| Files | ||
| Issue | Article in Press |
|
| Section | Research Article(s) | |
| Keywords | ||
| Strong ion gap anion gap acid-base disorders cirrhosis intensive care unit. | ||
| Rights and permissions | |
|
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. |
