#3235 ELECTROLYTE DISORDERS IN COMMUNITY-ACQUIRED ACUTE KIDNEY INJURY
Authors: Porta Jose Maria Peña , Mayor Paula Juarez , Saumell Mireia Pujol , Gascó José Antonio Ferreras , Babara Axenia , Gil Pablo Iñigo 
Published: June 2023

Abstract

Background and Aims
The kidney plays a decisive role in regulating the homeostasis of the internal environment. Acute kidney injury (AKI) compromises the kidney's ability to maintain this regulation intact, and the appearance of various electrolyte disorders is to be expected in this situation. There are few data in the literature that describe these alterations in patients with community-acquired AKI (CA-AKI). The purpose of this study is to analyze the incidence of electrolyte disorders in a cohort of patients with CA-AKI admitted to the nephrology service of a tertiary level hospital.

Method
This is a single-center, observational, longitudinal, and retrospective study based on a cohort of patients with CA-AKI admitted to the Nephology Service of a third level hospital from January 2010 to December 2018. We analyzed the incidence of changes in sodium, potassium, chloride, bicarbonate, calcium, and phosphorus in these patients and their clinical consequences during admission and follow-up after hospital discharge.

Results
A total of 639 patients were included in the final analyses. The mean age was 72,93±13,38 years. 61,7% were men. Charlson comorbidity index was 5,87 ±2,4 points. The length of stay was 11,63±10,14 days. In view of the Etiology of AKI, 72,1% had prerenal AKI and 27,9% non-prerenal. 436 patients had a history of previous chronic kidney disease (CKD) (68.23%). AKI KDIGO stages were: stage I, 105 cases (16.4%); stage II, 67 cases (10.5%); stage III 467 cases (63.1%). Hemodialysis (HD) was required in 114 patients (17.8 %). 62 patients (9.7 %) died during hospital stay. The percentage of patients with alterations in the different ions was: chlorine 54%, potassium 60.1%, sodium 45.23%, bicarbonate 85.67%, calcium 52.68%, phosphorus 54.49%. The most frequent ionic alterations at a global level were low bicarbonate (78.3%), hyperkalemia (53.05%), hypocalcemia (49.6%) and hyponatremia (41.5%). No significant differences were observed in these percentages when comparing patients with previous CKD with respect to carriers of normal baseline renal function (glomerular filtration rate &gt; 60 ml/min). When analyzing whether electrolyte alterations occurred simultaneously: 2.2% of cases did not present any, 6.3% only one, 18.2% two, 26.4% three, 26.1% four, 14.9% five and 5.9% six simultaneous alterations. In the univariate analysis, patients with hypernatremia (Chi square 22.7; p &lt; 0.001), hyperkalemia (Chi square 9.7; p = 0.008) and hyperphosphatemia (Chi square 18.5; p &lt; 0.001) had higher mortality during admission. In the multivariate analysis using logistic regression, the variables that were independently associated with mortality during hospitalization were phosphorus (OR 1.425; 95% CI 1.212 - 1.676) and chlorine (OR 1.045; 95% CI 1.002 - 1.089). In the follow-up after hospital discharge, the Kaplan-Meier curves in the univariate analysis showed higher mortality in patients who presented hyperkalemia (log rank test: Chi square 15.5; p &lt; 0.0001), hypernatremia (log rank test: Chi square 47.7; p &lt; 0.0001), hypocalcemia (log rank test: Chi square 6.73; p &lt; 0.034) and hyperphosphatemia (log rank test: Chi square 10.24; p &lt; 0.006). In the multivariate analysis using Cox regression, the variables that were independently associated with mortality after hospital discharge were sodium (Exp(B) 1.001; 95% CI 1.002 - 1.048; p = 0.048), potassium (Exp(B) 1.140; 95% CI 1.055 - 1.233; p = 0.001) and phosphorus (Exp(B) 1.087; 95% CI 1.023 - 1.048; p = 0.154).

Conclusion
In our series of patients with CA-AKI, we detected a high prevalence of electrolyte disorders, without a history of previous CKD having any influence on it. The most frequent was the finding of three or four simultaneous alterations. Phosphorus and chlorine independently influenced mortality during admission. In the follow-up after hospital discharge, sodium, potassium, and phosphorus were independent predictors of mortality. The clinician who treats cases of CA-AKI must expect the appearance of frequent electrolyte disorders and must be prepared for their correct management.