Fluid overload and changes in serum creatinine after cardiac surgery: predictors of mortality and longer intensive care stay. A prospective cohort study

Maria Irigoyen,Edemar Costa Pereira,Cassian Belettini,Fernanda Consolim-Colombo,Willian Menegazzo,Lilian Araújo,Júlio Viégas,Anna Stein,Renato Eick,Lucas de Souza

doi:10.1186/cc11368

Abstract

IntroductionFluid overload is a clinical problem frequently related to cardiac and renal dysfunction. The aim of this study was to evaluate fluid overload and changes in serum creatinine as predictors of cardiovascular mortality and morbidity after cardiac surgery.MethodsPatients submitted to heart surgery were prospectively enrolled in this study from September 2010 through August 2011. Clinical and laboratory data were collected from each patient at preoperative and trans-operative moments and fluid overload and creatinine levels were recorded daily after cardiac surgery during their ICU stay. Fluid overload was calculated according to the following formula: (Sum of daily fluid received (L) - total amount of fluid eliminated (L)/preoperative weight (kg) × 100). Preoperative demographic and risk indicators, intra-operative parameters and postoperative information were obtained from medical records. Patients were monitored from surgery until death or discharge from the ICU. We also evaluated the survival status at discharge from the ICU and the length of ICU stay (days) of each patient.ResultsA total of 502 patients were enrolled in this study. Both fluid overload and changes in serum creatinine correlated with mortality (odds ratio (OR) 1.59; confidence interval (CI): 95% 1.18 to 2.14, P = 0.002 and OR 2.91; CI: 95% 1.92 to 4.40, P <0.001, respectively). Fluid overload played a more important role in the length of intensive care stay than changes in serum creatinine. Fluid overload (%): b coefficient = 0.17; beta coefficient = 0.55, P <0.001); change in creatinine (mg/dL): b coefficient = 0.01; beta coefficient = 0.11, P = 0.003).ConclusionsAlthough both fluid overload and changes in serum creatinine are prognostic markers after cardiac surgery, it seems that progressive fluid overload may be an earlier and more sensitive marker of renal dysfunction affecting heart function and, as such, it would allow earlier intervention and more effective control in post cardiac surgery patients.

Highlights

Fluid overload is a clinical problem frequently related to cardiac and renal dysfunction
When we analyzed the association of fluid accumulation and changes in serum creatinine by Z score variables with mortality, we observed that fluid overload and changes in serum creatinine were significantly associated with mortality
Our analysis describes the importance of fluid overload and changes in serum creatinine during the perioperative period following cardiac surgery as early markers of intra-ICU mortality and longer ICU stay

Summary

Introduction

Fluid overload is a clinical problem frequently related to cardiac and renal dysfunction. The aim of this study was to evaluate fluid overload and changes in serum creatinine as predictors of cardiovascular mortality and morbidity after cardiac surgery. Fluid overload has been linked with worse prognosis in several situations, including heart failure [6,7]. Due to this close interaction, fluid overload has been identified as a new biomarker of heart and renal function [8]. In kidney and in heart dysfunction, fluid overload is generally regarded as an important clinical condition [9,10]. Fluid overload often remains symptomless for several days until clinical symptoms set in, when treatment is usually initiated [12]

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