Insensible water loss in Italian intensive care units: a nationwide survey on its integration into daily fluid balance and quantification practices

Background: Fluid balance monitoring is a common practice in intensive care units (ICUs) to assess the volemic status of critically ill patients. However, its accuracy is limited in estimating insensible water loss (IWL), a component that is difficult to quantify but potentially significant. Literature shows considerable heterogeneity in the methods used to estimate IWL, with limited standardisation. Aim: To assess its use, a nationwide cross-sectional survey was conducted, targeting adult ICUs in Italy. The aim was to evaluate the extent to which IWL is included in daily fluid balance calculations and to describe the methods used for its estimation. Materials and methods: The survey consisted of a 26-item questionnaire and was distributed via REDCap software from March 10, 2025 to April 10, 2025. Results: Responses were obtained from 100 ICUs, of which 75 were included in the final analysis. Of these, 70.6 % reported including IWL in fluid balance assessments. Among these, 79 % used a specific formula, with the most frequently adopted being 0.5 ml/kg/hour (52 %). The main parameters considered in the calculation were body weight (83 %), body temperature (86.6 %), and type of ventilatory support (60.3 %). Furthermore, 73.6 % of respondents considered IWL to be moderately or extremely relevant. Conclusions: Findings suggest that IWL is widely taken into account in clinical practice, although with heterogeneous approaches. Our results highlight the need for future physiological studies to standardise its estimation and improve the accuracy of fluid balance assessments in critically ill patients. Implications for clinical practice: This paper underlines the lack of evidences and standardisation in IWL’s estimation. It provides available alternatives and foundation for further investigations.