Management of BTMPS Toxicity

Overview

• BTMPS poisoning should be treated using calcium‑channel‑blocker (CCB) protocols, with first‑line agents — intravenous calcium, high‑dose insulin, and vasopressors (norepinephrine or epinephrine) — selected according to the dominant clinical picture of bradycardia, hypotension, or cardiogenic shock. 1, 2

Mechanism and Clinical Presentation

• BTMPS acts as a non‑competitive L‑type calcium‑channel blocker and a use‑dependent nicotinic acetylcholine‑receptor antagonist; toxicity therefore presents with classic CCB cardiovascular effects and should follow established CCB poisoning management pathways. 1
• Typical findings include cardiac conduction abnormalities on electrocardiogram and possible progression to cardiogenic shock due to myocardial dysfunction. 1

Initial Assessment and Supportive Care

• Immediate actions: obtain large‑bore IV access and begin continuous cardiac monitoring. 1
• If ingestion was recent and the patient is asymptomatic, consider gastrointestinal decontamination (e.g., activated charcoal). 1

First‑Line Therapies

Intravenous Calcium

• Calcium chloride 2000 mg IV (≈20 mg/kg in pediatric patients) is recommended, followed by a maintenance infusion of 20–40 mg/kg/h.
• Titrate the infusion to achieve target blood pressure while keeping ionized calcium ≤ 1.5–2 × the laboratory upper‑normal limit; administer through a central line, especially in children. 2, 3
• Calcium alone often fails to reverse severe toxicity and should be combined with additional agents when needed. 4

High‑Dose Insulin Therapy

• Give an initial bolus of 1 U/kg regular insulin, then start a continuous infusion of 1–10 U/kg/h.
• Monitor closely for hypoglycemia, hypokalemia, and volume overload throughout therapy.
• Insulin markedly improves myocardial contractility in cardiogenic shock and should be initiated early in the treatment course. 2, 5, 3, 4

Vasopressors

• Norepinephrine is the preferred first‑line vasopressor (up to 100 µg/min in adults).
• Epinephrine is added when cardiogenic shock predominates. 4, 1

Second‑Line Therapies for Refractory Cases

Atropine (Symptomatic Bradycardia)

• Dose 0.5–1.0 mg IV every 3–5 min (maximum 3 mg; pediatric ≈0.02 mg/kg).
• Clinical response is frequently inadequate; atropine alone should not be relied upon. 2, 3, 6, 4

Intravenous Lipid Emulsion (ILE)

• Administer a 1.5 mL/kg bolus, then infuse 0.25 mL/kg/min for up to 30 min.
• Routine use is not supported by current evidence; reserve ILE for cases refractory to calcium, insulin, and vasopressors. 2, 5, 3, 4

Methylene Blue (Vasodilatory Shock)

• Give 1–2 mg/kg intravenously; repeat hourly if needed, not exceeding a cumulative 5–7 mg/kg.
• Hemodynamic responses are variable and often transient. 2, 5, 3, 4

Electrical Pacing (Unstable Bradycardia/High‑Grade AV Block)

• Consider temporary pacing when bradyarrhythmia persists without severe myocardial dysfunction.
• Outcomes are mixed, especially when AV nodal blockade coexists with vasodilatory shock. 1, 4

Advanced/Rescue Therapies

Veno‑Arterial Extracorporeal Membrane Oxygenation (VA‑ECMO)

• Indicated for refractory shock or periarrest states; reported survival up to 77 % in CCB overdose cohorts.
• Initiate early because circuit setup requires time; most beneficial when refractory shock has a dominant cardiogenic component. 1, 2, 7, 4, 8

Cardiac Arrest Management

• Follow standard ACLS algorithms, adding IV calcium, lipid emulsion, and VA‑ECMO when available. 7, 1, 2

Pitfalls and Recommendations

• Do not postpone high‑dose insulin; it should be started early rather than as a last‑resort measure. 8
• Avoid relying solely on atropine for bradycardia, as failure rates are high. 4
• Keep ionized calcium ≤ 2 × the upper‑normal limit to prevent iatrogenic complications. 2, 3
• Reserve ILE for refractory toxicity; routine use is not evidence‑based. 4
• Aggressively monitor for hypoglycemia and hypokalemia during insulin therapy. 2, 5, 3
• Early consultation with a poison‑control center is advised for complex presentations. 1, 8

Adjunctive Therapies

• Glucagon (2–10 mg bolus followed by 1–15 mg/h infusion) may be used as an adjunct; response is variable, vomiting is common, and rapid tachyphylaxis can develop. 2, 3, 4

Peripheral Administration of Calcium Gluconate and Implications for Bicarbonate Concentration

Safety Considerations

• When 10 % calcium gluconate is administered via a peripheral line to reduce vein irritation (as opposed to calcium chloride), the same principle applies to sodium bicarbonate—using lower‑concentration bicarbonate solutions (e.g., 7.5 % rather than 8.4 %) is safer for peripheral veins. 9