Comparison of Different Methods of Superior Vena Cava Flow Measurment in Preterm Infants

Objectives: Echocardiographic assessment of hemodynamic status is a determining factor in the adequate treatment of patients in the neonatal intensive care unit. Superior vena cava (VCS) flow represents surrogate marker for systemic blood flow. We hypothesized that superior vena cava flow velocity measurements obtained by using a suprasternal or high parasternal view are comparable with those obtained from a subcostal long and short axis, as well as using modified method including VCS area measurements. We also hypothesize positive correlation between SVC flow and flow on middle cerebral artery.

Methods: a prospective, single center, observational study in Pediatric Clinic, CCU Sarajevo, including 50 preterm infants. The enrolment period is June 2021 to June 2022. Accepted permissible variability of the VCS flow value between individual measurement methods was +/- 20ml/kg/min.

Results: Using standard protocol flow over superior vena cava median value was 74.3 ml/kg/min (63.1-87.9), while using the second standard protocol median value was slightly higher 80.8 ml/min/kg (64.8-100.1). Median flow value for modified method was 75.5 (67.5-99.7) ml/kg/min. Median flow value with second modified technique was 86.5 (68.1-98.6) ml/min/kg. We found positive correlation with middle cerebral artery pulsality index (rho=0.284; p=0.046), which points that when flow on vein cava superior was increasing flow on middle cerebral artery was increasing too. We found no correlation with the resistance index. Regarding anterior cerebral artery no statistically significant correlation were found.

Conclusion: Different approaches to measuring VCS flow have justification and clinical utility, while respecting potential limitations.

Keywords: SVC flow, preterm infant, cerebral flow.