Cardiovascular system response to intravenous administration of physiologic sodium chloride solution in healthy subjects

Introduction . Infusion therapy, despite all its advantages, is not fully understood regarding its impact on the cardiovascular system when large volumes of fluid are used. Objective . To assess the response of the cardiovascular system to massive infusion load in 5 healthy individuals. Materials and Methods . The study included 5 healthy volunteers (2 men and 3 women), with a mean age of 31.6±5.3 years, mean weight of 73.25±15.8 kg, and mean body surface area of 1.83±0.2 m². The study protocol involved the administration of 0.9 % sodium chloride solution through a peripheral catheter for ≈10 hours during the daytime over 2 days, at a volume of 2.2 L/m² body surface area per day. Before the start of the experiment, as well as 48 hours (2 days) and 168 hours (7 days) after the start, all participants underwent measurements of body weight, blood pressure (BP), heart rate (HR), blood tests for NT-proBNP levels, and transthoracic echocardiography. Results . The study found no significant changes in BP, HR, and body weight. A significant increase in NT-proBNP level was noted, rising from 29.3±17.67 ng/ml to 295.4±136.1 ng/ml (p=0.018) after 48 hours of infusion, followed by a decrease (38.0±20.94 ng/ml, p=0.020) and normalization after 7 days. Additionally, after 48 hours, there was an increase in the volume of the left atrium (from 39.2±9.0 ml to 58.2±10.7 ml; p=0.003), basal size of the right ventricle (from 3.44±0.18 cm to 3.66±0.26 cm; p=0.020), and vertical size of the right atrium (from 4.12±0.24 cm to 4.56±0.37 cm; p=0.032), as well as an increase in the amplitude of tricuspid annulus systolic excursion (TAPSE) – from 2.5±0.27 cm to 2.94±0.25 cm; p=0.034) and the E/e’ index (from 3.87±0.52 to 4.83±0.35; p=0.015. Conclusion . Intravenous administration of large volumes of 0.9 %NaCL is associated with an enlargement of the right heart chambers, with enhanced contractility of the right ventricle, increased volume of the left atrium, elevated left ventricular filling pressure, and a marked increase in NT-proBNP. NT-proBNP level should be estimated outside of infusion therapy.