Intercostal catheterisation. An alternative approach to the paravertebral space

Twenty-one patients scheduled to undergo thoracotomy or median sternotomy had intercostal catheters inserted pre-operatively. During thoracotomy, under direct vision, the spread of 20 ml of a solution containing bupivacaine and methylene blue was followed. In most cases the spread involved one or two intercostal spaces. However, in all but one patient, dye spread medially to the paravertebral space where it then spread in both caudad and cephalad directions to reach between two and five vertebrae. In three cases, dye was seen crossing the anterior surface of the vertebrae to reach the contralateral aspect. It is concluded that a major component of dermatomal block during intercostal catheterisations may be secondary to paravertebral spread.