The relative position of femoral artery and vein in children under general anesthesia--an ultrasound-guided observational study.

Background: Femoral artery overlaps femoral vein by varying degrees distal to the inguinal ligament, which may result in difficult venous access and also increases the risk of arterial puncture.

Objective: To study the size of femoral vessels and the degree of overlap in children undergoing anesthesia using ultrasound at 1 and 3 cm distal to inguinal ligament.

Methods: A prospective observational study, 84 children aged <7 years were recruited in six different age groups. An experienced anesthetist identified the femoral vessels and their overlap using ultrasound at two fixed points distal to the inguinal ligament. We also evaluated the correlation of skin puncture site marked as per Advanced Paediatric Life support (APLS) guidance using landmark technique with the ultrasound location of femoral vein beneath the same site.

Results: The percentage of children with overlap of femoral vein by femoral artery increases from 5% to 60% as we move distal to the inguinal ligament. At 3 cm distal to inguinal ligament, the incidence of any degree of overlap was statistically significant (P < 0.05) in children <5 years. In 80% of children, the femoral vein was located by ultrasound beneath the skin puncture site as recommended by APLS guidelines.

Conclusion: A significant increase in femoral vein overlap occurs as we move distal to the inguinal ligament. There is one in five chance of failure to locate femoral vein by landmark technique. In children <2 years, a high approach to femoral vein cannulation under ultrasound guidance is recommended.