To Assess the Technical Feasibility of Ultrasound Lumbar Sympathetic Block with Electrical Stimulation Needle in Out-of-Plane Needle Orientation: A Prospective Interventional Study

Objective: We describe the technical feasibility of a new technique of ultrasound lumbar sympathectomy validated by fluoroscopy. Design: Prospective interventional study. Setting: Pain block area. Subjects: Thirty patients with peripheral arterial disease with pain at rest (numerical rating score [NRS] ≥3) were recruited. Methods: In the lateral position, a curved probe (FUJIFILM SonoSite Edge, Bothell, WA, USA, 2-5 MHz) was placed transversely at the iliac crest. An electrical stimulation needle was inserted out of plane, below the lower pole of the kidneys, directed anterior to the vertebral body below. When the needle tip was not visualized, a current of 2.0 A was applied. Patients' quadriceps contractions, ultrasound psoas contractions, and bone contact guided needle placement, which was confirmed on fluoroscopy. Other parameters noted were the number of needle insertions, vertebral level, pain NRS at baseline and at 4 hours, 24 hours, 1 week, and 2 weeks after block, temperature rise, and any other complications. Results: In all patients, the needle tip was correctly placed in one to three attempts. In 73% of patients, the needle tip was at L3. Baseline pain NRS was 8 (interquartile range 7-8), which decreased to 2 (interquartile range 2-3) at 1 week after the procedure, and it was maintained in this range until 2 weeks later. A temperature rise of >2ºC was noted in all patients. Conclusion: Ultrasound lumbar sympathectomy can be performed safely in patients with peripheral arterial disease by an out-of-plane approach in the lateral patient position with an electrical stimulation needle. Before injection of the drug, aspiration of blood should be ruled out in view of the possibility of aortocaval injection.