1. Cadaver study on spread of injectate in the Serratus anterior muscle plane (SAP) Dr. Veena Daga (ST7 Anaesthesia, University Hospitals of Leicester NHS Trust), Dr. M Narayan (Consultant Anaesthetics - Frimley Park Hospital Health NHS Foundation Trust), Dr. Jatin Dedhia, Consultant Anaesthetics, United Lincolnshire Hospitals NHS Trust, Lincoln), Dr. H Crick (Head of Anatomy-Medical and Social Care Education, University of Leicester.), Dr. Atul Gaur (Consultant Anaesthetics - University Hospitals of Leicester NHS Trust) BACKGROUND Serratus anterior muscle plane (SAP) block has been recently described for post-operative pain relief following breast surgery and in trauma cases. It may be a safe alternative to other regional technique such as thoracic paravertebral and central neuraxial blockade. There has been no descriptive cadaver study in literature to our knowledge that describes delineation of plane for this new technique. OBJECTIVES To assess the SA morphology i.e. formation of muscle belly/plane. To assess the use of air-water contrast in delineating the spread of injectate on ultrasound. To evaluate the extent of vertical spread of injectate in Serratus Anterior muscle plane. SUMMARY The use of agitated water contrast under ultrasonography technique has number of advantages such as portability of imaging equipment, low cost of contrast media, ease of handling and avoidance of defacement of cadaver, thus allowing the use of same cadavers for subsequent anatomical dissection training. Secondly, in our study most of the cadavers had a well formed Serratus anterior muscle belly just before the posterior axillary line. Hence the ideal position for injection in to SAP should be in the posterior axillary line for ultrasound-guided injections for optimal spread of injectate. Thirdly, the study showed that the extent of cephalad spread was variable. In majority of cadavers, the cephalad spread was up to 3rd inter-costal space, suggesting that the SAP block would cover dermatomes T3 to T9. Finally, we limited the volume of injectate to 30 mls total in our study, which was adequate to cover 3rd to 9th Rib level in most cases. The extent of spread may vary and depend on factors such as site of incision planned, height and weight etc. The spread of injectate in patients may not be same as in cadavers as other factors may influence the spread of injectate. Gender4 male, 3 female Age50-91 years Serratus anterior plane36% Mid-axillary line 50% Between posterior and mid- axillary line 14% Posterior axillary line Lower limit of spreadSubcostal margin Upper limit of spread7% 2nd ICS 71% 3rd ICS 22% 4th ICS (ICS – intercostal space) RESULTS CONCLUSIONS REFERENCES MATERIALS & METHODS Seven cadavers were studied bilaterally in prone position. Ethical permission was obtained from University of Leicester Medical School GE 12L-RS Linear Ultrasound Probe and 21G 100mm Stimuplex needle was used. Scanning was performed in anterior axillary line(Fig. A) and posterior axillary line (Fig. B) Injection site - posterior axillary line at intercostal space 4/5 level (Fig. C). 20 ml Normal saline followed by 10 ml Air-Water contrast (8 mls water and 2 cc air) was injected under real time USG. Spread of hyperechoic air bubbles was observed in real time on ultrasound in SAP plane (Fig. D). Air-water contrast use was successful in delineating SAP in all cadavers. A well formed Serratus Anterior plane was located in posterior axillary line. In none of the cadavers the Serratus Anterior plane was formed in anterior axillary line. The injections should be made in posterior axillary line or posterior to this for a proper spread of the injectate. 30 ml was adequate to delineate the SAP Spread varied caudally and sidewise. This study shows a relatively economical and effective approach of using agitated water contrast ultrasonography to delineate muscle plane. R. Blanco, T. Parras, J. G. McDonnell and A. Prats-Galino. Serratus plane block: a novel ultrasound-guided thoracic wall nerve block. Anaesthesia 2013, 68, 1107–1113 Kunhabdulla NP, Agarwal A, Gaur A et al. Serratus anterior plane block for multiple rib fractures. Pain Physician. 2014 Jul-Aug;17(4):E553-5. De Cosmo G, Aceto P, Gualtieri E, Congedo E. Analgesia in thoracic surgery: review.Minerva Anestesiol. 2009 Jun;75(6):393-400. Epub 2008 Oct 27..Wenk M, Schug SA Peri erioperative pain management after thoracotomy. Curr Opin Anaesthesiol. 2011 Feb;24(1):8-12 Meierhenrich R, Gorsewski G, et al Analgesia and pulmonary function after lung surgery: is a single intercostal nerve block plus patient- controlled intravenous morphine as effective as patient-controlled epidural anaesthesia? A randomized non-inferiority clinical trial.Br J Anaesth. 2011 Apr;106(4):580-9. Aristomenis et al Can anaesthetic technique for primary breast cancer surgery affect recurrence or metastasis? Anesthesiology. Oct 2006; 105(4): 660–664. Tips for Inserting Graphs or Images Note: Skip the following procedure if your graphs were created in PowerPoint®, Illustrator (eps file) or Excel. Image checking procedure: After you insert the image (72 dpi screen resolution) and resize* to fit, right click on it and select Format Picture. When the pop-up window comes up, click on size and check the scale. The image will print better if its width and height scale is at 25% or lower (20% or 10%, etc.) If the scale of the image is higher than 25%, try to replace it with a larger size (more dpi, e.g. 300dpi) image if possible. (Note: This should not be done by manually stretching the image to a larger size.) 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This is only a reminder.) A - Ultrasound image of incomplete Serratus muscle belly in anterior axillary line B - Ultrasound image of complete belly formation in posterior axillary line C - Ultrasound image of in plane view of needle and hypoechoic fluid in plane D - Ultrasound image of hyper echoic air bubbles in plane DISCUSSION