Elsevier

Journal of Critical Care

Volume 36, December 2016, Pages 140-145
Journal of Critical Care

Outcome / Prediction
The prognostic value of the strong ion gap in acute pancreatitis

https://doi.org/10.1016/j.jcrc.2016.06.035Get rights and content

Abstract

Purpose

In this study, we aimed to evaluate the predictive value of Stewart-derived parameters for the development of severe type of acute pancreatitis (AP) and for AP-related mortality.

Methods

We studied 186 patients admitted to the hospital with AP. We performed blood gas and biochemical analysis for each patient on admission. We calculated multiple metrics according to the Stewart's acid-base theory and assessed their accuracy as predictors of AP severity and mortality.

Results

Of the 186 patients presenting with AP, 85 (45.7%) developed severe AP and 33 (17.7%) died during hospitalization. Patients with severe AP had significantly higher median strong ion gap (SIG) than did patients with mild or moderate AP (7.88 vs 2.11 mEq/L, P< .001). In multivariate logistic regression analysis, SIG had an odds ratio (OR) of 1.56 (P< .001). In addition, SIG had good predictive power for mortality (OR, 1.26; P= .014) as well as acute kidney injury (OR, 1.34; P< .001).

Conclusions

In a cohort of patients with AP, SIG was a strong independent predictor of severity and mortality. Besides, SIG might also be an early marker for acute kidney injury in AP patients. Additional research is needed to identify the nature of the unmeasured anions responsible for such findings.

Introduction

Acid-base disorders are common in critically ill patients and associated with high mortality [1], [2], [3]. In patients with acute pancreatitis (AP), such disorders are often present on admission to the intensive care unit (ICU) [4], [5]. The epidemiology and clinical significance of such disorders in AP, however, are poorly understood.

The traditional method for interpreting acid-base disorders is based on the Henderson-Hasselbalch equation [6], which is then coupled with the anion gap (AG) [7] and clinical assessment to define the presence of specific metabolic or respiratory acid-base states. However, the traditional method has been criticized for not taking into account the impact of hypoalbuminemia, disorders of phosphatemia, and the presence and impact of unmeasured anions when used improperly (without correction for hypoalbuminemia) [8], [9], [10]. Stewart's approach offers an alternative paradigm for the interpretation of acid-base disorders and allows for quantification of the effects of changes in strong ion difference (SID), albumin and phosphate levels, and unmeasured anions (strong ion gap [SIG]).

Two studies have shown that SID and SIG correlate with hospital mortality in trauma patients [11], [12]. Moreover, the prognostic value of SIG was also confirmed in other critically ill patients [13]. More recently, Sharma et al [5] also found that arterial pH, bicarbonate levels, and base deficit at presentation were early markers for predicting adverse outcome in AP. However, no information exists on the predictive value of acid-base variables as estimated by the Stewart approach in patients with AP.

The purpose of our investigation was to evaluate how acid-base variables obtained at the earliest stages of AP and analyzed according to the Stewart model may help predict subsequent AP severity and AP-related mortality.

Section snippets

Patients and materials

We conducted a retrospective, cohort study in the surgical ICU of Jinling Hospital, Nanjing, China, a tertiary referral center for the treatment of AP. The data collection for this study was approved by the institutional review board of Jinling Hospital. Patients with a primary diagnosis of AP admitted to our center from September 2010 to June 2014 were screened for potential inclusion. Diagnosis of AP required 2 of the 3 following criteria: (1) abdominal pain consistent with the disease, (2)

Results

During the study period, 980 patients with AP were screened and 794 were excluded (see the details in Fig. 1), leaving 186 consecutive patients for analysis. Their demographic data are shown in Table 1. The study patients had an overall mortality of 17.7%. In total, 24 (72.7%) patients died of septic shock and multiple-organ failure, 4 (12.1%) died of uncontrolled intra-abdominal hemorrhage, 2 (6.1%) died of tracheal hemorrhage, and the last 3 died of middle cerebral artery aneurysm rupture

Key findings

We conducted a retrospective observational study to identify predictors of severity and outcome in a large cohort of AP patients from a tertiary referral center for pancreatitis in China before fluid resuscitation. We aimed to evaluate whether the Stewart analysis might help predict severity, mortality, and AKI in adult AP patients with simple and routine clinical tests. Our results suggested that SIG was an accurate predictor of severity of AP and a moderate predictor of mortality and

Conclusions

In this study, we assessed the predictive value of the SIG in patients with AP. Our study demonstrated that an elevated SIG was a common phenomenon at the early stage of severe AP, that it was independently correlated with adverse outcomes, and that it was an accurate predictor of subsequent severity and mortality, suggesting that it could be used in the triage, risk stratification, management, and prognosis of such patients in the future.

Acknowledgments

This study was supported by the National Science Foundation of China (81300360). The funding agency had no role in study design, the collection of data, in the interpretation of data, in the writing of the article, or in the decision to submit the article for publication.

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