LIPID EMULSION THERAPY FOR LIFE-THREATENING FLECAINIDE TOXICITY

Abstract

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: We present a case of flecainide (FLC) toxicity secondary to renal failure treated with intravenous lipid emulsion (ILE) therapy. CASE PRESENTATION: The patient is a 63 year old female with a history of stage IVB uterine carcinosarcoma, chronic kidney disease and supraventricular tachycardia (SVT) on FLC. She was admitted with intra-abdominal hemorrhagic metastases. A rapid response was called due to hypotension, and she was noted to be oliguric for the previous 24 hours with a serum creatinine 2.5 mg/dL (baseline 1.3 mg/dL) and hyponatremic (126 mmol/L). EKG showed a new wide complex rhythm, at 78bpm, QRS widening to 280ms, and prolonged QTc of 631. She subsequently suffered a wide complex tachyarrhythmic cardiac arrest (CA), refractory to two shocks, with return of spontaneous circulation after treatment with sodium bicarbonate (NaHCO3). FLC was discontinued and the patient was started on a hypertonic NaHCO3 drip, but frequent NaHCO3 pushes were required to correct widening of the QRS complex. The hypotension progressed requiring high dose infusions of epinephrine (15 mcg/min) and norepinephrine (90 mcg/min). ILE infusion was started, 20% lipid 1.5 mL/kg administered over 5 minutes, followed by an infusion of 0.25 mL/kg/minute over two hours. A serum FLC level was drawn during ILE infusion and came back elevated at 1.35 mcg/mL (therapeutic level 0.20-1.0 mcg/mL). In the 48 hours following ILE, there was resolution of the wide complex arrhythmias, and vasopressor requirements were reduced by more than 50% DISCUSSION: FLC is a class 1C antiarrhythmic that inhibits Na+ channels and is used for prevention of SVT. It has a narrow therapeutic range and about 30% is renally excreted making acute kidney injury a risk for toxicity. Other risk factors for toxicity are hyponatremia and hypokalemia. Characteristic signs of toxicity include hypotension, lethargy and EKG changes such as QRS widening and PR prolongation. These changes can progress to wide complex brady or tachyarrhythmic CA as seen in our patient. Standard of care is administration of hypertonic NaHCO3 which acts both as a Na+ load to compete with FLC for binding at Na+ channels and as an alkalinizing agent which decreases the ionized receptor-binding form of FLC. However, when NaHCO3 treatment fails, there are few other well studied options. One is VA-ECMO for which our patient was not a candidate. The other is lipid emulsion therapy, which is hypothesized to work by creating a lipid sink to sequester the drug and also has some positive ionotropy. CONCLUSIONS: In our patient, administration of ILE resulted in significant clinical improvement. Unfortunately, the clinical improvement did not sustain after several days and due to overall poor prognosis, the patient was eventually transitioned to comfort measures. REFERENCE #1: Subedi R, Dean R, Chaudhary A. Flecainide toxicity in renal failure. Proc (Bayl Univ Med Cent). 2018 May 9;3(3):328-330. REFERENCE #2: Ghataoura R, Patil S. Flecainide toxicity: a presentation to the emergency department with literature review. BMJ Case Rep. 2020 Feb 28;13(2):e232691. doi: 10.1136/bcr-2019-232691. PMID: 32114494; PMCID: PMC7050315. REFERENCE #3: Valentino MA, Panakos A, Ragupathi L, Williams J, Pavri BB. Flecainide Toxicity: A Case Report and Systematic Review of its Electrocardiographic Patterns and Management. Cardiovasc Toxicol. 2017 Jul;17(3):260-266. doi: 10.1007/s12012-016-9380-0. PMID: 27435408. DISCLOSURES: No relevant relationships by Rebecca Fieles, source=Web Response No relevant relationships by David Gerber, source=Web Response No relevant relationships by Brian Park, source=Web Response No relevant relationships by Harry Rockower, source=Web Response No relevant relationships by Diana Solomon, source=Web Response No relevant relationships by Yanika Wolfe, source=Web Response