Anesthetic Spread of Ultrasound-Guided Paraspinal Blocks in Video-Assisted Thoracoscopic Surgery: A Three-Dimensional Reconstruction Image Study

Background: Anesthetic spread of ultrasound-guided paraspinal blocks is still unknown. Objectives: To compare the drug diffusion qualities of intertransverse process block (ITPB) and erector spinae plane block (ESPB) in clinical practice. Study Design: Prospective computed tomography (CT)-3-dimensional (3D) reconstruction image study. Setting: Operation room in hospital. Methods: Twenty patients undergoing thoracoscopic pulmonary wedge resection or segmentectomy were enrolled. These procedures require localization of pulmonary nodules using CT-guided needle puncture immediately before surgery. The patients were divided into 2 groups, each consisting of 10 patients. Group I underwent ITPB, while group E underwent ESPB. These interventions were performed 30 minutes before surgery using 20 mL of 0.25% bupivacaine with 2 mL iohexol. Sensory loss of the thoracic dermatomes was assessed using cold stimulation before general anesthesia. Patients' CT localization images were used for 3D reconstruction after surgery, and the diffusion of the drug in each cross-section of the CT images was evaluated. Results: Three-dimensional imaging of the drug showed that in group E, drug diffusion was improved in the cephalocaudal area compared to group I (10 vs 4.5 segments). Drug diffusion in group I was improved anteriorly and laterally ([10/10, 100%] in the paravertebral and intercostal spaces) and reached the front of the vertebral body along the thoracic fascia in certain segments (6/10, 60%). In group E, very few segments of the drug reached the paravertebral (2/10, 20%) and intercostal (3/10, 30%) spaces. All patients in group I had clear signs of loss of cold sensation on the lateral and anterior chest walls, with an average of 4 thoracic dermatomes. In group E, 3 patients had definite lateral and anterior chest wall cold stimulation signs, the thoracic dermatome was discontinuous, and the effect was only present between 1-2 segments. The blocking effect of the paraspinal zone was excellent (100%) in both groups. Limitations: However, this study has some limitations. First, the sample size was small, and clinical trials with larger samples are required to further verify the effects of ITPB and ESPB. Second, the same local anesthetic drug concentration and volume were used for both techniques in this study, and the effect of volume or concentration on drug diffusion was not further explored. Conclusions: Compared with ESPB, ITPB yielded increased stability in lateral and anterior chest wall block with improved anterior and intercostal spread, but reduced cephalocaudal spread.