A prospective evaluation of psoas muscle and intravascular injection in lumbar sympathetic ganglion block.

Background: Intravascular and intramuscular injection of local anesthetics during lumbar sympathetic ganglion block (LSGB) can cause false positive or negative results in a diagnostic block, and complications. In the present study, we prospectively evaluated the incidence and possible factors causing intravascular and IM injection during LSGB.
Methods: We evaluated 216 LSGBs in 83 patients. All LSGBs were performed by 1 of the authors using a 3-needle technique. After final needle position was confirmed by biplanar fluoroscopy, an aspiration test was conducted, and 1 mL of contrast was injected sequentially. Incidences of psoas muscle injection, blood flashback, and the presence of intravascular contrast spread on static and real-time fluoroscopy were assessed.
Results: The incidence of psoas muscle injection of contrast was 21.3% (46/216), and it was associated with the level of injection (L2) significantly (chi(2) = 14.773, P = 0.001). The incidence of intravascular injection of contrast was 12.5% (27/216). Among 27 cases of documented intravascular injections, 5.1% (11/216) of patients showed contrast spread at the area where the sympathetic ganglion was presumed to be and to the vessels simultaneously, and 7.4% (16/216) of patients showed only intravascular injection of contrast. The sensitivity of the aspiration test and static radiography were 40.7% and 70.4%, respectively.
Conclusions: LSGB at the L2 level showed the lowest incidence of psoas muscle injection of contrast in comparison with LSGB at L3 and L4. The aspiration test and static radiography frequently missed the intravascular injection of contrast during LSGBs.