The Journal of the Arkansas Medical Society Med Journal Sept 2019 FInal 2 | Page 17

Medical Board Legal Issues? Call Pharmacist/Attorney Darren O’Quinn 1-800-455-0581 Figure 2: Dissection down to the PIF plane shows that the injectate spread throughout the PIF plane entirely, proving involvement of the anterior cutaneous branches of the intercostal nerve. Lateral spread of injectate is likely to involve the lateral cutaneous branch of the intercostal nerve as well. In this figure the pectoralis major muscle (PMM) is reflected bilaterally. A 12 cm ruler is placed in the midline over the sternum at the base of the sternal notch. The sternal head of the sternocleidomastoid muscles (SH) are indicated bilaterally. METHODS With the approval of the UAMS Institutional Review Board, five lightly embalmed cadavers were obtained from the Department of Anatomy. The cadavers were embalmed in house using the methods described by Anderson, stored at 4 degrees Celsius until the day of use, taken out the morning of the procedure and allowed to warm to room temperature for six-to-eight-8 hours. 8 Under ultrasound guidance, methylene blue dye was injected into the PIF plane of each hemi-chest wall of each cadaver for a total of 10 hemi-chest walls. For each left-side hemi-chest wall, a single injection was performed at the level of the fourth rib, into which 20mL of dye was injected. For each right-side hemi-chest wall, two separate injections at the third and fifth ribs were performed; 10mL of dye was injected at each site. In total, each hemi- chest wall was injected with 20mL of dye. A draped, linear-array NextGen LOGIQ e ultrasound transducer (GE Healthcare UK, Ltd., Chalfont, Buckinghamshire, UK) was used. The ultrasound probe was placed 2 cm laterally from the sternal border in the parasagittal plane, and the indicated rib was identified. A two-inch echogenic 20-gauge block needle (B. Braun Medical Inc., Bethlehem, PA, USA) was then advanced using an in-plane technique from cephalad to caudad starting at the superior border of the probe until the needle tip was seen between the pectoralis major muscle (PMM) and the external intercostal membrane (EIM). After a test dose of 1-2 mL of normal saline to confirm correct needle placement by hydrodissection, the indicated volume of blue dye (equal parts 0.25% methylene blue dye with normal saline) was injected through the needle. (Fig. 1) After the injection was complete, the injectate was allowed to settle for 20 minutes. An experienced anatomist then dissected the chest wall down to the PIF plane. RESULTS Dissection of the cadavers confirmed successful injection in nine of the 10 hemi-chest walls and showed that the dye spread entirely throughout the PIF plane (Fig. 2). One injection of a left hemi-chest wall failed due to incorrect needle- tip placement within the PMM. The mean single- injection (left side) maximal superior-inferior spread was 13.75 cm (standard deviation 2.10 cm). The mean double-injection (right side) maximal superior inferior spread was 16.63 cm (standard deviation 3.67 cm). The mean single-injection maximal lateral spread was 12 cm (standard deviation 2.16 cm). The mean double-injection maximal lateral spread was 12.25 cm (standard deviation 1.70 cm). The single-injection achieved a mean intercostal- space spread of 4.75 spaces (standard deviation 0.5 spaces). The double-injection achieved a mean intercostal-space spread of 5.75 spaces (standard deviation 1.22 spaces). www.DarrenOQuinn.com Little Rock, Arkansas MAKE THE SMART CHOICE, ADVERTISE IN: For more advertising information, contact Penny Henderson at 501.224.8967 or [email protected] > Continued on page 66. NUMBER 3 SEPTEMBER 2019 • 65