Emergency Medicine Hub / Toxicology & Environmental • 3 min read • 2 sections

Beta-Blocker Toxicity & High-Dose Insulin (HIET)

Evidence-based emergency management of beta-adrenergic antagonist overdoses: lipophilicity, membrane-stabilizing activity (sodium channel blockade by propranolol, carvedilol), intrinsic sympathomimetic activity, sotalol potassium-channel block and Torsades de Pointes, early fluid resuscitation, high-dose insulin euglycemia therapy (HIET: 1 unit/kg/hr to 10 units/kg/hr), IV glucagon rescue, calcium salts, and venoarterial ECMO indications.

Resuscitation Quick Actions • First 2 Minutes

High-Acuity

HIET Bolus & Infusion

Regular Insulin 1 unit/kg IV bolus + 1 unit/kg/hr infusion (titrate up to 5–10 units/kg/hr for refractory cardiogenic shock)

Dextrose Support

D50W 1–2 amps (25–50g) IV bolus, followed by 10% or 20% Dextrose infusion at 100–250 mL/hr; maintain glucose 100–250 mg/dL

Glucagon Bridging Dose

5–10 mg IV push over 1–2 minutes; if HR/BP improves, start continuous infusion at 2–5 mg/hr (premedicate with ondansetron)

QRS Widening (Propranolol)

Sodium Bicarbonate 1–2 mEq/kg IV push (100–150 mEq) for QRS > 100 ms (membrane stabilizing effect)

Sotalol QT Prolongation

Magnesium Sulfate 2g IV over 10 min; maintain potassium 4.5–5.0 mEq/L; overdrive pacing or isoproterenol for TdP

Extracorporeal Life Support

VA-ECMO (E-CPR) consult early for cardiogenic shock refractory to HIET, vasopressors, and inotropes

Bottom-Line Clinical Pearl

Beta-blocker toxicity classically presents with profound bradycardia, hypotension, cardiogenic shock, and hypoglycemia. Propranolol carries the highest fatality rate due to CNS penetration (seizures, coma) and fast sodium-channel blockade (QRS widening). First-line targeted inotrope therapy is High-Dose Insulin Euglycemia Therapy (HIET) started at 1 unit/kg bolus followed by 1 unit/kg/hr infusion with concurrent 10–25% dextrose. Glucagon (5–10 mg IV push) acts as a bridge but causes refractory vomiting and tachyphylaxis.

1. Pathophysiology & Drug-Specific Mechanisms

Beta-adrenergic antagonists competitively bind beta-1 (cardiac inotropy, chronotropy, dromotropy), beta-2 (bronchial and vascular smooth muscle relaxation, glycogenolysis), and beta-3 (lipolysis) receptors, inhibiting G-protein coupled adenylyl cyclase and diminishing intracellular cyclic AMP (cAMP). Without cAMP, protein kinase A cannot phosphorylate L-type calcium channels, severely curtailing intracellular calcium entry during systole.

Unique Toxin Property	Exemplar Agents	Distinct Clinical Manifestations & Lethality
Membrane-Stabilizing Activity (MSA)	Propranolol, Carvedilol, Acebutolol	Fast myocardial sodium-channel blockade produces profound QRS prolongation, ventricular arrhythmias, rapid CNS penetration causing seizures and coma.
High Lipophilicity	Propranolol, Metoprolol, Timolol	Crosses the blood-brain barrier rapidly; leads to early respiratory depression, obtundation, and generalized status epilepticus.
Potassium Channel Blockade (Class III)	Sotalol	Blocks delayed rectifier potassium current (IKr), causing marked QT prolongation, ventricular bigeminy, and recurrent Torsades de Pointes.
Intrinsic Sympathomimetic Activity (ISA)	Pindolol, Acebutolol	Partial agonist properties can paradoxically produce resting tachycardia and hypertension before precipitating sudden cardiac collapse.

2. High-Dose Insulin Euglycemia Therapy (HIET) Protocol

In cardiogenic shock from beta-blocker or calcium channel blocker poisoning, the stressed myocardium switches from its preferred fuel source (free fatty acids) to carbohydrates (glucose). Toxic shock suppresses pancreatic insulin release while inducing marked peripheral insulin resistance. High-dose insulin exerts a potent direct inotropic effect by driving glucose into cardiomyocytes, restoring cytoplasmic calcium levels, and improving sarcoplasmic reticulum pump function.

Step/Component	Dosing & Administration	Target Endpoints & Monitoring Pearls
Step 1: Baseline Lab Check	Check fingerstick glucose and serum potassium	If glucose < 200 mg/dL, give 1 amp D50W (25g). If K+ < 3.0 mEq/L, repletion is required before large insulin bolus.
Step 2: Insulin Bolus	Regular Insulin 1 unit/kg IV push	Administer over 1 minute. Do not delay waiting for specialized pumps.
Step 3: Continuous Insulin Infusion	Regular Insulin 1 unit/kg/hr IV	Titrate up every 15–30 minutes by 1 unit/kg/hr up to 5 to 10 units/kg/hr until MAP > 65 mmHg and cardiac output recovers.
Step 4: Dextrose Infusion	D10W or D20W at 100–250 mL/hr	Target blood glucose 100–250 mg/dL. Check fingerstick glucose every 15–30 minutes until stable, then q1h.
Step 5: Potassium Monitoring	Check serum K+ q1h for first 4–6 hours	Insulin shifts K+ intracellularly. Do NOT aggressively treat K+ unless < 2.8–3.0 mEq/L, as total body stores are preserved.

Critical Pitfall / Contraindication

CRITICAL PITFALL: Do not rely solely on glucagon or atropine. Glucagon provides transient inotropy via non-adrenergic cAMP generation, but depletes hepatic glycogen within 1–2 hours, triggers massive intractable emesis (increasing aspiration risk during altered mental status), and does not sustain survival in severe overdoses. Start HIET immediately; do not treat it as a last resort.

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