Figure 1. Cross-section of thorax at the level of the T11 vertebral body demonstrating anatomy relevant to insertion of paravertebral sympathetic (splanchnic) catheters. The needles, although visible in their entirety in the diagram, are inserted at an acute angle to the horizontal plane shown. The initially inserted narrow, pencil-point needles are shown in dotted outline. The tips of the paravertebral catheters can be seen exiting the larger-bore Tuohy needles, shown in continuous outline. A = aorta; AV = azygous vein; D = diaphragm; HAV = hemiazygous vein; IVC = inferior vena cava; RLL = right lower lobe of lung; Snn = splanchnic nerves; TD = thoracic duct; T11 = 11th vertebral body.