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Background and Aims While advances in regional anaesthesia have enhanced safety in anaesthetic procedures, systemic toxicity from local anesthetics (LAST) remains a significant risk. This risk is influenced by factors such as the method and location of anaesthetic application, and patient comorbidities. Lidocaine, in particular, is frequently implicated in these events.

Methods We report the case of a 70-year-old female, 65kg, ASA-PS 4E, presenting with several comorbidities including frailty, hypertension, dyslipidemia, diabetes mellitus, heart failure, atrial fibrillation, and chronic pulmonary disease. The patient underwent urgent femoro-distal thromboembolectomy for acute lower limb ischaemia under monitored anesthesia care, with subcutaneous lidocaine administered by the surgeon.

Results The patient was administered 0.05mg of fentanyl and 0.625mg of droperidol intravenously, and 400mg of 2% lidocaine administered subcutaneously in fractioned doses in the femoral region. Approximately 2 minutes after lidocaine administration, the patient experienced a sudden altered state of consciousness, with disorientation and agitation, along with a rapid ventricular response in atrial fibrillation. Suspecting LAST, treatment with a 20% Intralipid® infusion was initiated, with a rapid restoration of her baseline mental and cardiac status. A subsequent CT scan confirmed the absence of acute cerebral events. After 24h in intensive care without further complications, the patient was discharged to the ward. The remaining postoperative course was unremarkable.

Conclusions Prompt recognition and treatment of LAST are imperative, particularly in patients with significant comorbidities. This case highlights the need to consider the risk of systemic toxicity even with subcutaneous infiltration of local anesthetics, a procedure frequently performed with large volumes by non-anesthesiologists.