[The relationships between the head-down angles and the internal jugular vein cross-sectional areas in regard to the patients' heights and the venous flattening ratios in children].

BACKGROUND: The head-down tilt is thought to increase the cross-sectional areas (CSAs) of the vein in central venous catheterization. In this study, the effectiveness of the head-down tilt was investigated in children. METHODS: Forty patients were divided into two groups: L (n = 20) less than 8.3 kg and H (n = 20) more than 8.3 kg in weights. Right IJVs were described with the ultrasound echo at the middle of the neck. The maximal width (W) and thickness (T) of the IJVs were measured at 0, 10, and 20 degrees head-down. The IJV CSAs and the flattening ratios were calculated as pi x W x T x 2(-2) and as 1-T/W respectively. It is considered significant when the CSA increase ratio is more than 20%. RESULTS: Patients were 9.0 in median months of age. The increase ratio of CSA in group H at 10 degrees was 27% when the flattening ratios at 0 degrees were more than 0.30. In group L the increases in ratios of CSA were less than 5% when the flattening ratios at 0 degrees were less than 0.30. CONCLUSIONS: The head-down at 10 degrees effectively increased the CSA when the IJV flattening ratios at 0 degrees was more than 0.3 in group H.