| Abstract |
Background: Fluid overload leads to organic complications, prolonged stay of the patient on mechanical ventilation, and even death. The patient's fluid balance is a biomarker indicating the severity of the condition. Late correction with diuretics or renal replacement therapy not only fails to change the consequences of fluid overload but can also cause more complications. Alternatively, initially restricting and adjusting the type of fluids yields better outcomes for patients. Despite these strategies, fluid overload coexists in patients with acute kidney injury. Even if the acute kidney injury is overcome, patients are at an increased risk of developing chronic kidney failure and comorbidities in the future.
Objective: The main aims of the study are to record the characteristics of fluids administered on the day before admission and during the first three days of hospitalization in the adult ICU, along with their correlation with the 24-hour and overall fluid balance. The secondary aims are to correlate fluid balance, type, and category of fluids administered during the first three days of ICU stay with the development of acute kidney injury and patient outcomes.
Methods: This is a retrospective monocentric observational study of adult patients admitted to the ICU of the University Hospital of Heraklion, Crete, during the period 2017-2023. Patients aged 18 to 100 years, with a hospital stay longer than 72 hours, were included in the study. Various data were recorded, including demographic characteristics, anthropometric measurements, individual medical history, laboratory tests, arterial blood gas analysis (worst values during the first 3 days in the ICU separately), assessment of acute kidney injury according to KDIGO criteria, and the use of mRAI for adult patients. Disease severity indicators, clinical indicators at admission, and recording of worst values within the first 24 hours were also documented. Outcome indicators for patients were assessed, as well as pre-admission fluid intake in quantity and type, and detailed recording of fluids administered during the first 3 days of ICU stay and on the 7thday if applicable. Daily and cumulative fluid balance was recorded, and Fluid Overload [% (Lt/Kg)] was calculated for each day and cumulatively for the 3rd and 7th day. Statistical analysis of the data was conducted using SPSS 29.0 statistical software. The significance level was set at α=0.05.
Results: A total of 100 patients participated, mainly pathological admissions, with comorbidities in 84% of patients and ICU mortality reaching 32%. 52% of patients had developed AKI on admission, with 40.4% mortality. No significant difference in overall patient outcome was found between the different types of solutions administered, i.e., between balanced crystalloids and N/S 0.9%, as well as between crystalloids and colloids, with their pre-ICU administration being quite deficient. Fluids administered widely involved balanced crystalloid solutions, mainly Ringer's Lactate, Plasma-Lyte and combinations with D/W solutions as well as more specific use of N/S 0.9%. Possible hyperchloremia due to N/S 0.9% was not observed in this study, with acidosis and elevated lactate values in the first 3 days being findings in patients with high (FO%) (p<0.05, p=0.021). Creep fluids were a significant part of the fluid balance on all recording days and at the occurrence of FO. Cumulative balance and (FO%) were significantly higher in patients who died on the 3rd (p=0.005, p=0.003) and 7th (p=0.018) days of hospitalization. Treatment of AKI through CRRT was associated with higher mortality compared to the use of diuretics (p=0.013). Abnormal mRAI at 1st 24 hours was associated with increased ICU (p=0.019) and hospital (p=0.002) mortality in 49 patients, while at 1st 24 hours, high RAI and mRAI values were also associated with increased patient mortality.
Conclusion: Fluid overload in ICU patients is associated with the occurrence of AKI, with intravenous administration of balanced crystalloid solutions and the use of N/S 0.9% in specific practices to help maintain Cl values. The treatment of AKI with CRRT as well as high RAI and mRAI values during the 1st 24 hours are associated with increased mortality, making the mRAI index an important predictive factor in the occurrence of AKI and mortality. It appears that mRAI can predict better the probability of death in the ICU compared to other indicators of renal function in the 1st 24 hours.
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