Varying anatomical injection points within the thoracic paravertebral space: effect on spread of solution and nerve blockade.

The factors responsible for the spreading pattern of a single paravertebral injection are still uncertain. In this study, 28 patients were randomly assigned to receive a paravertebral injection of radio-opaque dye (10 ml, with or without co-administration of 20 ml of local anaesthetics) either dorsal or ventral to the endothoracic fascia. The point of injection was determined by use of a nerve-stimulator and the radiographic distribution pattern was assessed blindly by a radiologist. Injections made in the more ventral part of the thoracic paravertebral space, supposedly anterior to the endothoracic fascia, resulted in a multisegmental longitudinal spreading pattern, whereas injections made dorsal to the endothoracic fascia resulted in a less predictable cloud-like spreading pattern, with only limited distribution over adjacent segments. The use of a nerve stimulator-guided technique appears to enhance the likelihood of achieving the more desirable longitudinal spreading pattern.