[Difference in the Spread of Injectate between Ultrasound Guided Pectoral Nerve Block I and II. A Cadaver Study].

BACKGROUND: Pectoral nerve block (PECS block) is first reported by Blanco et al, and mainly used for analgesia for breast surgery in Japan. However, the spread of PECS block is unclear.
METHODS: Ultrasound guided PECS I and II blocks were performed in a cadaver, and the cadaver was dissected for evaluation of the spread of coloring matter.
RESULTS: The coloring matter by PECS I block was spread to the axillary region between the major and minor pectoral muscles, while PECS II block remained over the fascia of the serratus muscle from mid-clavicular line to middle axillary line. Two possible routes to the axillary region by PECS I include: dorsal to the pectoral minor muscle through the clavipectoral fascia, and over the pectoral minor muscle to the axillary sheath.
CONCLUSIONS: Our cadaveric evaluation suggests that PECS I block produces more analgesia of the axillary region than PECS II. Further evaluation is needed in more cadavers.