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The serratus plane block is easy and appears to work very well for rib fracture analgesia by blocking the lateral intercostal nerves. Early on, but potentially a major advance.
At it most simple, the block is simply targeting the thoracic level (T3-T9 of the fracture, finding the rib around the mid-axillary line, the muscle overlying the ribs here is the serratus muscle. Guide your needle towards the rib and inject a large bolus of dilute local anesthetic ( e.g. 30cc total of 0.25% bupivicaine or 0.5% ropivicaine in a normal healthy adult) into the plane between the rib and serratus muscle.
There are many possible variations to this technique, but this is basic idea, keep reading for more details.
We began working with the PECS I and II for breast and axilla abscess I&D. This block is not difficult, but involves starting just under the clavicle, and identifying multiple tissue layers as you slide down and medial into the axilla. This is a great block that can provide total anesthesia. ( see below, this abscess managed in the ED just with a PECS II block.)
High Pecs block for the axilla
PA de la Torre 2016
Highland case performed with only a PECS II block and light sedation for anxiolysis
It turns out that for rib fractures, the procedure can be simplified even more down to just simply injecting a large deposit of local anesthetic over the ribs between the intercostal muscle and the serratus anterior muscle. As patients breathe, the local is distributed widely for a block centered at T3-T8.
Details of how this works
The block involves injecting 30-40cc dilute anesthetic ( e.g. 0.25% bupiv) over the serratus muscle OR under the serratus muscle ( the clinic effect is the same, with presumed continuity of the space) at about the T4-T5 level in the axillary region. The area is bounded by the latissimus muscle posteriorly and the pecs anteriorly. The injection can be made from the back the front or even caudal to cephalad.
A quick note of clarification: the serratus block will not block the pectoral nerves. For axillary anesthesia and breast anesthesia, a PECS block is needed. For chest tube placement, serratus may be sufficient.
Emergency Case: Injection over the serratus in a patient with 4-5-6 rib fractures. 30 minutes after block, pain free, able to cough and laugh without pain.
Emergency Case: Injection under the serratus in patient with 4-5-6-7 rib fractures. 30 minutes after block pain significantly relieved, declined further analgesia during ED stay.
Review Blanco's description below, fascinating development allowing blockade of the axilla and the rib cage without time-consuming, technically advanced paravertebral blocks or multiple intercostal blocks.
PECS II videos off yotube from LSORA and Sanford School of regional anesthesia