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Serratus Anterior Plane Block Anatomy — FRCA Final MCQ

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ModerateRegional AnaesthesiaSerratus Anterior Plane Block AnatomyFRCA Final

A 45-year-old woman (ASA II, 70 kg) is having a mastectomy under general anaesthesia. She receives a serratus anterior plane block for postoperative analgesia. What is the target plane for injection in a serratus anterior plane block?

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Correct answer: A — Into the erector spinae muscle

The serratus anterior plane (SAP) block targets the fascial plane either SUPERFICIAL to the serratus anterior muscle (between latissimus dorsi/pectoralis and serratus anterior) or DEEP to it (between serratus anterior and the external intercostal muscles/ribs). Local anaesthetic blocks the lateral cutaneous branches of the intercostal nerves (T2-T9) as they emerge through this plane. The superficial approach is more commonly described and technically easier under ultrasound guidance. The block is performed at the mid-axillary line, typically at the 4th-5th rib level, using 20-30 mL of LA.

Reference: Blanco R et al – 2013 – Serratus anterior plane block; RCOA – 2023 – Regional anaesthesia module