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Hypertonic sodium bicarbonate is advocated for the treatment of sodium channel blocker poisoning, but its efficacy varies amongst different sodium channel blockers. This Commentary addresses common pitfalls and appropriate usage of hypertonic sodium bicarbonate therapy in cardiotoxic drug poisonings. Serum alkalinization is best achieved by the synergistic effect of hypertonic sodium bicarbonate and hyperventilation (PCO2 ∼ 30–35 mmHg [0.47–0.6 kPa]). This reduces the dose of sodium bicarbonate required to achieve serum alkalinization (pH ∼ 7.45–7.55) and avoids adverse effects from excessive doses of hypertonic sodium bicarbonate. Tricyclic antidepressant poisoning responds well to sodium bicarbonate therapy, but many other sodium channel blockers may not. For instance, drugs that block the intercellular gap junctions, such as bupropion, do not respond well to alkalinization. For sodium channel blocker poisonings in which the expected response is unknown, a bolus of 1–2 mmol/kg sodium bicarbonate can be used to assess the response to alkalinization. Hypertonic sodium bicarbonate can cause electrolyte abnormalities such as hypokalaemia and hypocalcaemia, leading to QT interval prolongation and torsade de pointes in poisonings with drugs that have mixed sodium and potassium cardiac channel properties, such as hydroxychloroquine and flecainide. Excessive doses of hypertonic sodium bicarbonate commonly occur if it is administered until the QRS complex duration is < 100 ms. A prolonged QRS complex duration is not specific for sodium channel blocker toxicity. Some sodium channel blockers do not respond, and even when there is a response, it takes a few hours for the QRS complex duration to return completely to normal. In addition, QRS complex prolongation can be due to a rate-dependent bundle branch block. So, no further doses should be given after achieving serum alkalinization (pH ∼ 7.45–7.55). A further strategy to avoid overdosing patients with hypertonic sodium bicarbonate is to set maximum doses. Exceeding 6 mmol/kg is likely to cause hypernatremia, fluid overload, metabolic alkalosis, and cerebral oedema in many patients and potentially be lethal. We propose that hypertonic sodium bicarbonate therapy be used in patients with sodium channel blocker poisoning who have clinically significant toxicities such as seizures, shock (systolic blood pressure < 90 mmHg, mean arterial pressure <65 mmHg) or ventricular dysrhythmia. We recommend initial bolus dosing of hypertonic sodium bicarbonate of 1–2 mmol/kg, which can be repeated if the patient remains unstable, up to a maximum dose of 6 mmol/kg. This is recommended to be administered in conjunction with mechanical ventilation and hyperventilation to achieve serum alkalinization (PCO2∼30–35 mmHg [4-4.7 kPa]) and a pH of ∼7.45–7.55. With repeated bolus doses of hypertonic sodium bicarbonate, it is imperative to monitor and correct potassium and sodium abnormalities and observe changes in serum pH and on the electrocardiogram. Hypertonic sodium bicarbonate is an effective antidote for certain sodium channel blocker poisonings, such as tricyclic antidepressants, and when used in appropriate dosing, it works synergistically with hyperventilation to achieve serum alkalinization and to reduce sodium channel blockade. However, there are many pitfalls that can lead to excessive sodium bicarbonate therapy and severe adverse effects. [ABSTRACT FROM AUTHOR]

Hydroxychloroquine overdose is associated with myocardial toxicity and conduction disorders. We report a case of hydroxychloroquine overdose that demonstrated a rapid progressive intraventricular conduction delay and QT prolongation resulting in significant bradycardia and shock despite aggressive treatment. We describe the rare capture of abrupt abnormalities of this overdose in sequential electrocardiograms in the immediate hours post-ingestion. [ABSTRACT FROM AUTHOR]

Introduction: Patients with Fontan anatomy are at increased risk for exercise intolerance and early morbidity and mortality. QRS complex fragmentation (fQRS) and prolongation have been studied in multiple heart diseases, but their clinical importance is unknown in the Fontan population. Methods: A retrospective cross‐sectional study was performed. ECGs were evaluated for QRS prolongation (>98 percentile for age) and fQRS (≥3 R‐waves/notches in the R/S complex [more than two in RBBB] in ≥2 contiguous leads). The primary outcome measures were CPET performance. Results: Total 90 patients (median age 18 years, 57% male, 59% RV dominant) were included; 13% had fQRS and 31% had prolonged QRS. Demographically, patients with fQRS or prolonged QRS were like those without. Peak VO2 (64% vs. 63%, p.45), VE/VCO2 slope (85% vs. 88%, p =.74), and O2 pulse (149% vs. 129%, p =.83) were similar in the fQRS group versus those without. Upon multi‐variable regression, body mass index (β = ‐0.38, p <.01) and QRS duration (β = ‐0.29, p <.01) were independently associated with % predicted VO2; fQRS was not. Lower cardiac index (2.2 vs. 2.8 L/min/m2, p =.03) and higher ventricular end‐diastolic pressure (13 vs. 10 mmHg, p =.02) was seen with fQRS. Conclusions: QRS fragmentation is present in patients with Fontan physiology. fQRS showed no association with CPET performance but was related to invasive hemodynamic markers of ventricular performance. QRS duration may be a better predictor of exercise function following Fontan. [ABSTRACT FROM AUTHOR]

Bupropion is an antidepressant used in the treatment of major depressive disorder, seasonal affective disorder, nicotine addiction, and weight loss. It primarily functions via norepinephrine and dopamine reuptake inhibition. At toxic doses, bupropion can elicit seizures, as well as precipitate corrected QT interval (QTc) and QRS prolongation. We describe a case of an 18-year-old female who reportedly ingested 28 grams of extended-release bupropion, a dose much higher than in previously reported cases. Toxic ingestion precipitated status epilepticus, prolonged QTc, widened QRS, pulseless ventricular tachycardia (pVT), and subsequent cardiovascular collapse necessitating veno-arterial extracorporeal membrane oxygenation (ECMO) and Impella support. Historically, the cardiotoxic effects of bupropion toxicity have largely been treated with supportive care, sometimes requiring ECMO. This patient's course was complicated by a widening QRS despite aggressive bicarbonate therapy and recurrent pVT, which was ultimately aborted with lidocaine. Neurological prognostication was further complicated by a lack of brainstem reflexes on the exam. With maximal supportive care, the patient was liberated from Impella, ECMO, and the ventilator by hospital day seven. At discharge, she was neurologically intact with full recovery of cardiac function. This case emphasizes the need for early consideration of transfer to an ECMO center in the setting of a bupropion overdose and offers a potentially effective treatment option for bupropion-induced ventricular arrhythmia., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Reinsch et al.)