Obesity hinders ultrasound visualization of the subclavian vein: implications for central venous access

International policy statements from the US and the UK recommend real-time ultrasound guidance (USG) for placement of central venous catheters (CVCs) to improve patient safety. The evidence to support USG for the internal jugular (IJ) route is unequivocal; however, there is conflicting data on the effectiveness of USG in visualization of the subclavian vein (SCV). This study sought to determine whether body mass index (BMI) or clavicle shape affected SCV visualization with USG.

Forty-one emergency department patients were enrolled. Subject height and weight were recorded for BMI calculation. The clavicle shape was recorded as either flat or protuberant. USG was performed to identify the SCV vein in both the transverse and sagittal views. The ability to visualize the vein was rated on a three point rubric scale.

One subject had an underweight BMI, 18 a normal BMI, 12 an overweight BMI, and 10 an obese BMI. The improvement in the odds ratio (OR) of the ability to see the SCV in subjects with a normal compared to overweight/obese BMI was statistically significant (transverse view unadjusted OR=18.0 (95% CI 3.21-100.94), P=.001 and adjusted for a flat clavicle OR=10.54 (95% CI 1.41-78.37), P=.021).

Higher BMI and the presence of a flat clavicle limit the ability to visualize the SCV. These findings may help account for why USG for placement of SCV CVCs is less utilized. However, patients with a low/normal BMI and protuberant clavicle may benefit from USG when attempting SCV CVCs.