Methylene Blue Diffusion After Multilevel Thoracic Paravertebral Blocks

Abstract

Thoracic paravertebral nerve blockade (TPVB) has been reported to be used in different scenarios like cardiac, thoracic, and breast surgery; chronic pain management; and unilateral surgical procedures of the abdomen.1Karmakar M.K. Thoracic paravertebral block.Anesthesiology. 2001; 95: 771-780Crossref PubMed Scopus (375) Google Scholar, 2Davies R.G. Myles P.S. Graham J.M. A comparison of the analgesic efficacy and side-effects of paraverteral vs epidural blockade for thoracotomy—A systematic review and meta-analysis of randomized trials.Br J Anaesth. 2006; 96: 418-426Crossref PubMed Scopus (471) Google Scholar Few studies investigated local anesthetic spread into the paravertebral space.3Naja Z.M. El-Rajab M. Al-Tannir M.A. et al.Thoracic paravertebral block: Influence of the number of injections.Reg Anesth Pain Med. 2006; 31: 196-201PubMed Google Scholar, 4Karmakar M.K. Kwok W.H. Kew J. Thoracic paravertebral block: Radiological evidence of controlateral spread anterior to the vertebral bodies.Br J Anaesth. 2000; 84: 263-265Crossref PubMed Scopus (62) Google Scholar, 5Conacher I.D. Resin injection of thoracic paravertebral spaces.Br J Anaesth. 1988; 61: 657-661Crossref PubMed Scopus (44) Google Scholar Naja et al6Naja M.Z. Ziade M.F. El Rajab M. et al.Varying anatomical injection points within the thoracic paravertebral space: Effect on spread of solution and nerve blockade.Anaesthesia. 2004; 59: 459-463Crossref PubMed Scopus (85) Google Scholar observed 4 different spreading patterns of TPVB: pure longitudinal, longitudinal + intercostal, intercostal, and cloud-like. The purpose of our study was to evaluate the spreading patterns from the paravertebral space using a solution of methylene blue and local anesthetic. Ten patients scheduled for video-assisted thoracoscopy received 2 TPVB at T3 and T7 levels using a 20-mL solution of local anesthetic and methylene blue (ropivacaine, 100 mg-10 mL; methylene blue, 50 mg-5 mL; and saline, 5 mL). Paravertebral injection was performed after the induction of general anesthesia, with patients in the lateral position with one-lung ventilation according to the percutaneous approach technique described by Conacher and Slinger.7Conacher I.D. Slinger P. Pain Management.in: Kaplan Joel A. Slinger Peter D. Thoracic Anesthesia. (ed 3). Churchill Livingstone, Oxford, UK2003: 436-462Google Scholar The presence and spreading patterns of the solution into the paravertebral space were checked after the introduction of the thoracoscopy camera into the chest; the classification used was the same proposed by Naja et al.6Naja M.Z. Ziade M.F. El Rajab M. et al.Varying anatomical injection points within the thoracic paravertebral space: Effect on spread of solution and nerve blockade.Anaesthesia. 2004; 59: 459-463Crossref PubMed Scopus (85) Google Scholar In one patient we saw an intercostal spread from the vertebral bodies of T2 and T8 (Fig 1), in 4 patients a longitudinal diffusion from T2 to T8 and intercostal spreads at T2-T3 and T7-T8 were noted (Fig 2), in 2 patients we observed a cloud-like pattern at T2-T3 and T7-T8 (Fig 3), and in 3 patients we did not see any diffusion of the solution into the chest. No complications related to the block (pleural puncture, and vascular puncture) or methylene blue (neurotoxicity) were observed. A small amount of local anesthetic and methylene blue solution was found out of the thoracic paravertebral space and endothoracic fascia into the chest of all 7 patients. There was evidence of subparietal pleura hematoma at the T3 and T7 levels where the injections were performed in 1 of the 4 patients with longitudinal and intercostal spreads; this did not require any surgical actions. According to the pattern, the best block could be the one that allows longitudinal and intercostal diffusion.Fig 2Longitudinal and intercostal methylene blue diffusion. (Color version of figure is available online.)View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 3Cloud-like methylene blue diffusion. (Color version of figure is available online.)View Large Image Figure ViewerDownload Hi-res image Download (PPT)