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LAST Early Signs Day Case Recognition — FRCA Final MCQ

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ModerateRegional AnaesthesiaLAST Early Signs Day Case RecognitionFRCA Final

A 45-year-old man (ASA II) is having a vasectomy under local anaesthesia in the day unit. The surgeon infiltrates the spermatic cord bilaterally with 2% lidocaine. After the second injection, the patient complains of a metallic taste, circumoral numbness, and tinnitus. What has happened and what is the initial management?

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Correct answer: E — Anxiety attack – reassure only

Metallic taste, circumoral numbness, and tinnitus are the classic early warning signs of local anaesthetic systemic toxicity (LAST) – CNS excitation from sodium channel blockade. The LA has likely entered the systemic circulation (either intravascular injection or rapid absorption from the highly vascular spermatic cord). Immediate management: STOP further LA injection, administer 100% O2, call for help, establish IV access, and prepare Intralipid 20% (1.5 mL/kg bolus). Monitor closely for progression to seizures (CNS excitation peak) and then cardiovascular collapse (arrhythmias, cardiac arrest). Early recognition at the CNS stage allows intervention before cardiovascular toxicity.

Reference: AAGBI – 2020 – Management of severe LAST; RCOA – 2023 – Local anaesthetic toxicity