2025 FSA Podium and Poster Abstracts

Introduction: Local anesthetic systemic toxicity (LAST) is extremely rare in the pediatric population, occuring in 0.76 cases per 10,000 procedures (4). Infants are particularly vulnerable due to immature hepatic and renal function, reduced protein binding, and increased free drug concentrations, leading to higher susceptibility even at recommended doses (1,2). Here, we present a case of cardiac arrest in an infant following a paravertebral block (PVB) test dose with the aim of contributing to provider awareness and safer dosing practices in this high-risk population.

Case Report: A five-month-old, 8.3 kg term female presented for a left lower lobectomy via thoracotomy. Anesthesia induction and intubation were uneventful. During an ultrasound-guided left T4 PVB, she developed ventricular fibrillation immediately following a 2 mL test dose of 0.5% bupivacaine with 1:200,000 epinephrine.

A code was called, and return of spontaneous circulation (ROSC) was achieved after chest compressions, 50 mcg of epinephrine, and defibrillation. Suspecting LAST, 20% intralipid was administered as a 1.5 mL/kg bolus followed by a 0.25 mL/kg/min infusion. The infusion was stopped after 45 minutes but resumed when she re-entered ventricular fibrillation. ROSC was again achieved with chest compressions, 50 mcg of epinephrine, and another 1.5 mL/kg bolus of intralipid. The infusion continued until the daily maximum dose of 150 mL was reached. An ECMO alert was called but ultimately not required.

A bedside echocardiogram was unremarkable. Initial arterial blood gas revealed severe metabolic acidosis (pH 6.82). Lipidemia-induced dilutional anemia (Hgb 5.6) was treated with packed red blood cells. In the CVICU, follow-up ECG revealed QT prolongation, but she was extubated the next day, demonstrated appropriate neurological function, and was discharged without long-term complications. She returned two months later for an uneventful surgery, performed without a block.

Discussion: This case underscores the increased susceptibility of infants to LAST due to their unique pharmacokinetics (Table 1). A PVB carries a moderate to high risk of intravascular injection and LAST due to the vascularity of the paravertebral space and potential for multi-level injections. While its LAST risk is higher than distal peripheral nerve blocks but lower than intercostal blocks, proper technique—ultrasound guidance, aspiration, fractionated dosing, and vigilant monitoring—is essential to mitigate these risks.

Currently, no standardized guidelines exist for pediatric test dosing, particularly in infants. However, expert consensus suggests 0.1 mL/kg of LA with epinephrine (5 mcg/mL, 1:200,000) (3), equating to 0.5 mcg/kg of epinephrine. In this case, the 2 mL test dose administered exceeded this recommendation, potentially contributing to the cardiac arrest. Despite this, the test dose played a crucial role in preventing a more catastrophic outcome by allowing for immediate recognition and treatment of LAST.

This report highlights the importance of vigilance, dose consideration, and rapid intervention when using local anesthetics in pediatric patients. Increased awareness and further research into pediatric-specific dosing guidelines may help prevent similar events in the future.