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Cumulative LA Dose Calculation — FRCA Final MCQ

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HardRegional AnaesthesiaCumulative LA Dose CalculationFRCA Final

A 50-year-old otherwise healthy woman weighing 65 kg is undergoing bilateral transversus abdominis plane blocks. Before injection, the theatre team agrees to use its local levobupivacaine dose limit of 2 mg/kg, subject to an absolute maximum of 150 mg, and to include all levobupivacaine administered by both the anaesthetist and surgeon. She receives 20 mL of 0.25% levobupivacaine on each side. The surgeon then infiltrates the wound with 10 mL of 0.5% levobupivacaine. What is the total dose, and how does it compare with the agreed patient-specific limit?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — 150 mg – exceeds the limit

The correct answer is B. A 0.25% solution contains 2.5 mg/mL, so the bilateral TAP blocks deliver 40 × 2.5 = 100 mg. A 0.5% solution contains 5 mg/mL, so wound infiltration adds 10 × 5 = 50 mg. The cumulative dose is therefore 150 mg. The patient-specific limit is 2 × 65 = 130 mg; the 150 mg absolute maximum is a ceiling, not a dose permitted irrespective of weight. The total consequently exceeds the agreed limit by 20 mg. Option E applies only the absolute ceiling. Option D omits the surgeon's infiltration, while C and D result from incorrect concentration or volume conversion. Dose limits do not eliminate the risk of local anaesthetic systemic toxicity, which also depends on injection site and intravascular administration.

Reference: NHS Borders, Local Anaesthetic Dosing for Arthroplasty Guideline (Right Decisions, NHS Scotland) — levobupivacaine maximum 2 mg/kg with combined block-plus-infiltration dosing: https://www.rightdecisions.scot.nhs.uk/nhs-borders-clinical-guidelines/adult-acute-services/anaesthetics/local-anaesthetic-dosing-for-arthroplasty-guideline/