Comparison of Anatomic Landmarks and Ultrasound Guidance for Intercostal Nerve Injections in Cadavers Anuj Bhatia, MBBS, MD, FRCA, FRCPC, FIPP, FFPMRCA, EDRA,* Michael Gofeld, MD, FIPP,†‡ Sugantha Ganapathy, MBBS, DA, FRCA, FRCPC,§ John Hanlon, MSc, MD, FRCPC,∥ and Marjorie Johnson, PhD*¶ Background and Objectives: Intercostal nerve (ICN) injections are routinely performed under anatomic landmark or fluoroscopic guidance for acute and chronic pain indications. Ultrasound (US) is being used in- creasingly to perform ICN injections, but there is lack of evidence to support categorically the benefits of US over conventional techniques. We compared guidance with US versus anatomic landmarks for accuracy and safety of ICN injections in cadavers in a 2-phase study that included evaluation of deposition of injected dye by dissection and spread of con- trast on fluoroscopy. Methods: A cadaver experiment was performed to validate US as an imaging modality for ICN blocks. In the first phase of the study, 12 ICN injections with 2 different volumes of dye were performed in 1 cadaver using anatomic landmarks on one side and US-guidance on the other (6 injections on each side). The cadaver was then dissected to evaluate spread of the dye. The second phase of the study consisted of 74 ICN injections (37 US-guided and 37 using anatomic landmarks) of contrast dye in 6 non-embalmed cadavers followed by fluoroscopy to evaluate spread of the contrast dye. Results: In the first phase of the study, the intercostal space was identi- fied with US at all levels. Injection of 2 mL of dye was sufficient to ensure compete staining of the ICN for 5 of 6 US-guided injections but anatomic landmark guidance resulted in correct injection at only 2 of 6 intercostal spaces. No intravascular injection was found on dissection with either of the guidance techniques. In the second phase of the study, US-guidance was associated with a higher rate of intercostal spread of 1 mL of contrast dye on fluoroscopy compared with anatomic landmarks guidance (97% vs 70%; P = 0.017). Conclusions: Ultrasound confers higher accuracy and allows use of lower volumes of injectate compared with anatomic landmarks as a guidance method for ICN injections in cadavers. Ultrasound may be a viable alternative to anatomic landmarks as a guidance method for ICN injections. (Reg Anesth Pain Med 2013;38: 00–00) T he intercostal nerves (ICN) supply major parts of the skin and musculature of the chest and abdominal wall. Braun first described local anesthetic block of these nerves in 1907. 1 Intercostal nerve block is now commonly performed for treat- ment of acute and chronic pain conditions affecting the thorax and upper abdomen. Intercostal nerve block provides excellent analgesia for chest trauma such as rib fractures 2 and after chest and upper abdominal surgery such as thoracotomy, thoracostomy, mastectomy, gastrostomy, and cholecystectomy. 3 Intercostal nerve block is usually performed using anatomic landmarks and/or fluoroscopy guidance. Neither of these guid- ance techniques ensures accuracy or safety of ICN block. Fluo- roscopy also involves radiation exposure, higher cost, and the possible use of contrast dye, and a lack of availability and porta- bility often poses logistical challenges. Volumes of up to 4 mL are recommended for blockade of ICN, 2 but the results of a ca- daveric study suggest that with US guidance lower volumes could ensure ICN block. 4 Inability to visualize the pleura and blood vessels during ICN injection performed using anatomic land- marks or fluoroscopy exposes patients to risks of pneumothorax, hemothorax, injury to the lung, and intravascular injections. Ultra- sound (US) guidance allows the needle and injectate to be visual- ized in real time, and recent review articles on outcomes after nerve injections performed with US guidance suggest that it can enhance accuracy, efficacy, and safety. 5 Although a retrospective review comparing US and fluoros- copy for ICN blockade suggests equivalence for analgesia, 6 there is a lack of evidence for superiority or noninferiority of US over anatomical landmark-guided techniques. In this 2-phase investi- gation, we compared accuracy of US and anatomical landmark- guided approaches for ICN injections in cadavers by dissection and evaluation of spread of contrast dye on fluoroscopy. METHODS Institutional review board approval was not required because no personal information regarding the deceased individuals was available to the investigators. Approval was obtained for use of cadaveric material outside the anatomy department. Seven non- embalmed cadavers were used for this study. The mean age at death was 77 years, and the mean body mass index was less than 25 kg m − 2 . Bilateral ICN injections were performed on all cadavers in the prone position. Injections were performed using US-guidance on one side and anatomical landmarks on the other. US-guided Technique for Intercostal Injection This was performed according to the technique previously described in literature. 7 The intercostal space was identified using an L38 13 to 6 MHz linear transducer (M-Turbo; SonoSite, Bothell, Washington). The probe was initially placed in a trans- verse orientation over the midline to identify the tips of one of the midthoracic (fourth-eighth) vertebral spinous processes. The From the *Department of Anesthesia and Pain Management, University of Toronto and University Health Network-Toronto Western Hospital, Toronto, Ontario, Canada; †Departments of Anesthesiology and Pain Medicine; ‡Neu- rological Surgery, University of Washington, Seattle, WA; §Department of Anesthesiology and Perioperative Medicine, University of Western Ontario, London Health Sciences Centre, London; ∥Department of Anesthesia and Pain Management, University of Toronto and St Michael’ s Hospital, Toronto; and ¶Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. Accepted for publication July 23, 2013. Address correspondence to: Anuj Bhatia, MD, Department of Anesthesia and Pain Management, Toronto Western Hospital, University Health Network, 399 Bathurst St, McL 2-405, Toronto, Ontario, Canada M5T 2S8 (e‐mail: anuj.bhatia@uhn.ca). The authors declare no conflict of interest. Internal department funding and equipment support from SonoSite, Canada. Copyright © 2013 by American Society of Regional Anesthesia and Pain Medicine ISSN: 1098-7339 DOI: 10.1097/AAP.0000000000000006 ORIGINAL ARTICLE Regional Anesthesia and Pain Medicine • Volume 38, Number 6, November-December 2013 1 Copyright © 2013 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.