Ultrasound-Guided Serratus Anterior Block

The serratus anterior muscle is a fan-shaped muscle located on the lateral wall of the thorax. The majority of it is located deep beneath the scapula and pectoral muscles. The latissimus dorsi and pectoralis major muscles are easily palpated.

It is inserted precisely at the front edge of the scapula. The muscle is split into three sections:

· Upper / Superior: 1st to 2nd rib → superior angle of the scapula.

·  Middle / Intermedius: 2nd to 3rd rib → medial border of the scapula.

·  Lower / Inferior: 4th to 9th rib → medial border and inferior angle of the scapula. It is the most powerful and prominent part.

The main actions are protraction and upward rotation of the scapulothoracic joint, moving the scapula forward across the thoracic wall. It also keeps the medial border and inferior angle of the scapula close to the thoracic wall.

Serratus anterior muscle dysfunction is one of the causes of scapular winging. Weakness of the serratus anterior muscle allows the glenohumeral abductors to act unopposed, resulting in scapula downward rotation, inward rotation, and anterior tilt during shoulder abduction and flexion. If this position is maintained, the pectoralis minor muscle will shorten adaptively, resulting in more scapular anterior tilt and inward rotation.

The ultrasound-guided serratus anterior plane block (SAPB) is a promising single-injection method to anesthetize the chest wall in patients with multiple rib fractures, providing optimal emergency department care.

The SIFULTRAS-5.18 Wireless Linear Ultrasound Scanner has a frequency range of 5 to 10MHz and a depth of 9.6 cm for superficial applications. Indeed, SIFULTRAS-5.18 helps reduce the number of needle passes, shortens the block performance time, and accelerates the block onset time. Linear Ultrasound Probe is a special development of the Ultrasound Image Block Algorithm (UIBA, High-speed Parallel Image Block Algorithm), which is used to demodulate high frequency, high contrast, high resolution, and uniform B-mode/Color images.

SIFULTRAS-5.18 ensures a high-performance, dependable ultrasound imaging system solution. 

Because of its efficacy, relative ease, single-injection method, and limited side-effect profile, ultrasound-guided serratus anterior plane block (SAPB) has recently piqued the interest of anesthesiologists and pain physicians. SAPB is used by anesthesiologists in controlled environments such as OT or ICU for various breast surgeries and thoracotomy pain control. There is, however, limited literature on its feasibility and efficacy in the emergency department by emergency physicians (EP) for acute pain.

In conclusion, the ultrasound-guided SAPB offers an effective approach to the management of lateral chest wall pain, particularly in the context of traumatic rib fractures, and is a desirable alternative to opiate analgesia, especially in the elderly. 

References: Serratus Anterior (https://www.physio-pedia.com/Serratus_Anterior#:~:text=The%20serratus%20anterior%20muscle%20is,major%20and%20latissimus%20dorsi%20muscles)