Investigating the Anteroposterior Diameter of the Inferior Vena Cava as a Measure of the Adequacy of Fluid Therapy in Patients

Introduction: Investigating and adjusting the volume of intravascular fluids in many patients is significant for diagnosis, management, and evaluation of response to treatment. Measuring central venous pressure (CVP) is the preferred method of physicians to estimate or adequacy of fluid therapy in most cases. However, based on the studies, there is an interest in measuring the diameter of the inferior vena cava (IVC) using ultrasound as a non-invasive and fast method. However, there are several confounding factors and technical reasons to fear the accuracy of IVC measurements. It requires more studies in different groups. Thus, the present study investigates the anteroposterior diameter of the IVC after fluid therapy as a measure of the adequacy of fluid therapy and compares it with CVP.

Methods: This cross-sectional descriptive study was conducted at the Kausar Teaching Center of Kurdistan in 2022. The studied population included patients who need fluid therapy and were referred to the hospital. They were included in the study by a census method between the beginning of September and the end of October 2021 (two months). The inclusion criteria were patients with falls, burns, trauma, and accidents. The exclusion criteria also included other groups of patients and non-satisfaction of the patients. A radiology specialist and the sonography device, model ESAOTE MYLAB SIGMA, were used to measure the anteroposterior diameter of the IVC. Additionally, CVP was determined by central venous catheter. The demographic information was recorded in a checklist. Data were analyzed using SPSS16 software and Pearson correlation coefficient, and linear regression (P<0.05).

Results: Twenty-two patients were included in the study. The mean age of the patients was 37.88 ± 20.98. Most of them (54.5%) were male. The clients were burn patients (41%). The mean anteroposterior diameter of IVC was 13.80 ± 1.93 mm during inhalation and 13.32 ± 2.01 mm during exhalation. The mean CVP was 11.13 ± 1.62 cm of water. There was a significant and positive correlation between the anteroposterior diameter of IVC and CVP during inhalation (r=0.59, P=0.004). The correlation was positive and significant during exhalation (r=0.56, P=0.006). The results of linear regression analysis also revealed that for each unit of increase in IVC diameter, CVP increases by 0.495 units during inhalation. For each unit of increase in IVC diameter, CVP increases by 0.457 units during exhalation, which was significant.

Conclusion: Based on the results of the present study and similar studies, measuring the anteroposterior diameter of the IVC during inhalation and exhalation using ultrasound can be used as an indicator of the adequacy of fluid therapy. It is a non-invasive and quick method for patients suffering from burns and falls, trauma, and accident.