in this video we will show you how to scan and the soner anatomy required to perform aex 2 block there are numerous potential indications for this block such as breast surgery or any surgery involving the chest wall it should reliably provide analgesia between T1 and T5 this block is usually performed with 30 MS of 25% Leo bivan divided into two injections 10 ms between PEC major and pec minor and 20 Ms between PEC minor and seratus anterior care should be taken when performing bilateral blocks to ensure that the toxic dose is not exceeded we will now go through the neural innovation of the anterior chest wall and breast this consists of the supraclavicular nerve to the superior aspect of the chest wall the medial and lateral petral nerves responsible for sensory motor and sympathetic Innovation to the petral muscles the thoracodorsal nerve responsible for Innovation to latissimus dorsy the long thoracic nerve responsible for Innovation to seratus anterior and the lateral and anterior intercostal cutaneous nerve branches of T2 to T6 in this illustration we will go through the anatomy relevant to the PEX block underneath the skin and subcutaneous tissue lies the clavicle and pectoralis major muscle deep to pectoralis major lies pectoralis minor and in the plane between PC major and PEC minor lie the pectral branch of the thoro chromal artery and the lateral petral nerve at the lateral border of PEC minor you will see seratus anterior and the lateral intercostal cutaneous branches if we zoom in here on the image you will identify that the medial petrol nerve lies underneath PEC minor and pierces it at its medial border to lie in the same plane as a lateral petral nerve along with the petral branch of the thoro chromal artery to start scanning for the PEX block place the probe in a paramedian orientation just making contact with the clavicle similar to the position for an infraclavicular block the image generated will look like this with the clavicle demonstrated kead the pectoralis major muscle superficially deep to that PEC minor and you may also identify subclavius deep to the muscular structures you'll identify the auxilary artery and the auxilary vein if a rib is visualized it is likely to be the second rib and you can see the plura lying adjacent to it from this initial scan position the probe is slid down the patient's chest in a cad Direction counting the ribs as you go in this schematic you can see PEC major and pec minor the interfacial plane between them and the second and the third rib once the third rib is identified the probe is rotated through 90° and slid towards the lateral aspect of the chest wall once youve reached the lateral aspect of the Pectus minor muscle the image generated allows you to identify PEC major PEC minor one of the petral branches of the thoro chromal artery between the two of them and the third and fourth rib at this point this is the optimal position to site the peex block shown here is the needle insertion point over the anterior part of the chest Direct directed laterally in this block video you will see the needle introduced from the left hand side of the screen from the medle part of the chest wall directed laterally it's aiming to identify the fasal plane between PEC major superficially and pec minor deep to it as the local anesthetic is spreading you can identify the two pectral branches of the thoro chromal artery and a hyper aoic structure on the left of them which may well represent the lateral petral nerve after 10 ms of local anesthetic is in injected the needle is Advanced through PEC minor to identify the fasal plane between PEC minor and serrator anterior injection of 20 Ms of local anesthetic here is causing this fascial plane to open up and local anesthetic is directed laterally towards the axilla here are some tips to optimize your chances of success ensure that you have optimal ergonomics and positioning between yourself and the ultrasound machine you can either stand on the contralateral side of the patient needling along your line of sight or stand at the head end of the patient although you can needle this block in or out of plane we recommend inplane needling to optimize needle tip visualization when performing The Block ensure that you identify the pectral branches of the thoro chromal artery the plura and the needle tip at all times as an aid you can use the superior surface of the third or the fourth rib as a Target or a stop Gap to ensure that the needle does not Traverse deep to them towards the plura if performing bilateral blocks in patients less than 70 kg you may need to dilute down your local anesthetic to ensure that you don't go over the toxic level