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Repeat Block Cumulative LA Dose Safety — FRCA Final MCQ

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ModerateRegional AnaesthesiaRepeat Block Cumulative LA Dose SafetyFRCA Final

A 35-year-old man (ASA I) is having a shoulder arthroscopy under GA with an interscalene block. He receives 20 mL of 0.375% ropivacaine for the block. The block is effective. Two hours post-operatively, the surgeon asks for a repeat block for inadequate analgesia. When can a repeat block be safely administered?

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Correct answer: D — Wait 6 hours only

Repeat local anaesthetic blocks must respect cumulative dosing limits. The first block used 75 mg ropivacaine (20 mL × 3.75 mg/mL). Maximum ropivacaine dose: 3 mg/kg (~225 mg for 75 kg). While technically another 150 mg could be given within the max dose, plasma levels from the first block may still be significant at 2 hours (ropivacaine peak plasma after interscalene block occurs at ~30-60 minutes with a slow decline). Safest practice: wait until the first block has substantially worn off (>6-8 hours, ideally 12+ hours) before repeat injection, or use alternative analgesia.

Reference: BNF – 2025 – Ropivacaine dosing; AAGBI – 2020 – LAST prevention