Effects of Stellate Ganglion Block on Analgesia Produced by Cervical Paravertebral Block as Established by Quantitative Sensory Testing: A Randomized Controlled Trial

Abstract

Objective. To use quantitative sensory testing (QST) to assess whether a stellate ganglion block (SGB) modulates the analgesia induced by cervical paravertebral block (CPVB). Design. A prospective double-blind randomized controlled trial. Setting. Department of Anesthesia, Antwerp University Hospital, October 2011 to December 2015. Subjects. Twenty-eight adults scheduled for arthroscopy of a nonfractured shoulder were enrolled. Methods. Participants were randomly assigned to receive either single CPVB (5mL of levobupivacaine 0.5%) or combined CPVB+SGB (5mL and 3mL of levobubivacaine 0.5%, respectively). The detection thresholds for cold/warm sensations and cold/heat pain were established using thermal QST on the C4-C7 dermatomes before local anesthetic infiltration and at 0.5, 6, 10, and 24 hours thereafter. Our primary outcome was the time course of QST thresholds for the different neurosensitive/nociceptive modalities. As secondary and tertiary outcomes, we evaluated the degree of motor block and the time to first administration of rescue analgesics. Results. We randomized 20 patients. There were no significant differences in the detection thresholds for the neurosensitive/nociceptive modalities, motor block, or timing for rescue analgesics between the groups (P=0.15-0.94). All patients with CPVB+SGB exhibited Horner's signs, whereas patients in the CPVB group did not exhibit these signs; however, this does not exclude sympathetic block. Conclusions. We were unable to demonstrate any analgesic benefit of CPVB+SGB in arthroscopic shoulder surgery. It is therefore not unreasonable to suppose that pain from soft tissue injuries without bony lesions is transmitted mainly by somatic nerves with no or only minimal involvement of the sympathetic nervous system.