"Hidden Fluid" In The Critically Ill Patient: A Wake-Up Call

Background and Aim: Fluid overload and unfavorable outcomes in critically ill patients have been demonstrated in many clinical settings, such as acute lung injury/acute respiratory distress syndrome, septic patients, and those with acute kidney injury. Fluid overload has been reported in up to 70% of patients admitted to the intensive care unit (ICU). Fluid optimization strategies are often used to prevent fluid overload. Less obvious sources of fluid intake are often overlooked. The aim of this study was to determine the contribution of intravenous medications to daily fluid intake and balance in our ICU. Methodology: We conducted a retrospective study on adult patients admitted to the ICU of the University College Hospital, Ibadan, from January to December 2015. Daily ICU record charts were reviewed to determine the sources and volumes of various fluids for the study patients. Fluid other than intravenous fluid, enteral feeds, and blood/blood products were categorized as hidden fluid. These were mainly intravenous medications. Data were analyzed using the Statistical Package for the Scientific Solutions Version 20. Results: A total of 286 patients were admitted during the study year. There were 26 nonadults (<= 16 years) excluded, and the records of 74 patients were not available. The mean daily volume of drug solutions (473.4 ml) was about 16% of the mean daily intake (2846.1 ml). The percentage of hidden fluid was highest in the neurology group (26.7%). No group had <10%. The use of vasopressor was significantly associated with higher volume of hidden fluid (P = 0.001). Hidden fluid constituted 13% of the total fluid administered during the study period. Conclusion: Intravenous drug solutions were important contributions to fluid intake and balance in our review. ICU clinician should always consider this when calculating daily fluid maintenance. Further study is needed to determine their contribution to the development of fluid overload and ICU mortality.