Observational Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Crit Care Med. Feb 4, 2015; 4(1): 71-76
Published online Feb 4, 2015. doi: 10.5492/wjccm.v4.i1.71
Serum bicarbonate may independently predict acute kidney injury in critically ill patients: An observational study
Anuksha Gujadhur, Ravindranath Tiruvoipati, Elizabeth Cole, Saada Malouf, Erum Sahid Ansari, Kim Wong
Anuksha Gujadhur, Kim Wong, Department of Renal Medicine, Frankston Hospital, Frankston VIC 3199, Australia
Ravindranath Tiruvoipati, School of Public Health, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria 3800, Australia
Ravindranath Tiruvoipati, Elizabeth Cole, Saada Malouf, Erum Sahid Ansari, Department of Intensive Care Medicine, Frankston Hospital, Frankston VIC 3199, Australia
Author contributions: Gujadhur A, Cole E, Malouf S, Ansari ES and Wong K contributed to conception and design, acquisition of data, interpretation of data, drafting the manuscript and revising it critically for important intellectual content and have given final approval of the version to be published; Tiruvoipati R contributed to conception and design, acquisition of data, or analysis and interpretation of data; Tiruvoipati R had been involved in drafting the manuscript or revising it critically for important intellectual content; Tiruvoipati R had given final approval of the version to be published; all authors read and approved the final manuscript.
Ethics approval: Human Ethics Review Committee of Peninsuln Health hace reviewed (Ref HREC/11/PH/63) and approved the study for publication. a copy of approval can be provided on request.
Informed consent: The Human Ethics Review Committee of Peninsuln Health consent from individual patients as the study was seen as a retrospective audit of data routinely collected for patient care and not experimental research.
Conflict-of-interest: None of the authors have commercial association or financial involvement that might pose a conflict of interest in connection with this article.
Data sharing: Data presented in the manuscript is anonymised and the risk of identifying individual patient is very low. No additional data is available other than stated in the manuscript for this study.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Dr. Ravindranath Tiruvoipati, Department of Intensive Care Medicine, Frankston Hospital, 2 Hastings Road Frankston, Victoria 3199, Australia. travindranath@hotmail.com
Telephone: +61-431-279347 Fax: +61-3978-47398
Received: May 10, 2014
Peer-review started: May 10, 2014
First decision: June 6, 2014
Revised: December 27, 2014
Accepted: January 9, 2015
Article in press: January 12, 2015
Published online: February 4, 2015
Processing time: 277 Days and 8.2 Hours
Abstract

AIM: To explore whether serum bicarbonate at admission to intensive care unit (ICU) predicted development of acute kidney injury (AKI).

METHODS: We studied all patients admitted to our ICU over a 2 year period (February 2010 to 2012). The ICU has a case mix of medical and surgical patients excluding cardiac surgical, trauma and neurosurgical patients. We analysed 2035 consecutive patients admitted to ICU during the study period. Data were collected by two investigators independently and in duplicate using a standardised spread sheet to ensure accuracy. Ambiguous data were checked for accuracy where indicated. AKI was defined using the Kidney Disease Improving Global Outcomes criteria. Patients were divided into two groups; patients who developed AKI or those who did not, in order to compare the baseline characteristics, and laboratory and physiologic data of the two cohorts. Regression analysis was used to identify if serum bicarbonate on admission predicted the development of AKI.

RESULTS: Of 2036 patients 152 (7.5%) were excluded due to missing data. AKI developed in 43.1% of the patients. The AKI group, compared to the non-AKI group, was sicker based on their lower systolic, diastolic and mean arterial pressures and a higher acute physiology and chronic health evaluation (APACHE) III and SAPS II scores. Moreover, patients who developed AKI had more co-morbidities and a higher proportion of patients who developed AKI required mechanical ventilation. The multi-regression analysis of independent variables showed that serum bicarbonate on admission (OR = 0.821; 95%CI: 0.796-0.846; P < 0.0001), APACHE III (OR = 1.011; 95%CI: 1.007-1.015; P < 0.0001), age (OR = 1.016; 95%CI: 1.008-1.024; P < 0.0001) and presence of sepsis at ICU admission (OR = 2.819; 95%CI: 2.122-23.744; P = 0.004) were each significant independent predictors of AKI. The area under the ROC curve was 0.8 (95%CI: 0.78-0.83), thereby demonstrating that the predictive model has relatively good discriminating power for predicting AKI.

CONCLUSION: Serum bicarbonate on admission may independently be used to make a diagnosis of AKI.

Keywords: Acute kidney injury, Bicarbonate, Mortality, Sepsis

Core tip: Metabolic acidosis is often associated with acute kidney injury (AKI) and can result in multiple complications, including cardiac dysfunction, hypotension and mortality. There is however, a paucity of data regarding the value of metabolic acidosis, especially serum bicarbonate, in making an early diagnosis of AKI in an intensive care unit (ICU) setting. We demonstrated that serum bicarbonate on admission may independently be used to make a diagnosis of AKI, in a mixed ICU setting. Our results are relevant since serum bicarbonate is inexpensive and easily available, which will enable initiate prompt treatment of AKI, for better outcomes.