Makindo Medical Notes

Related Subjects: |Drug Toxicity - clinical assessment |Metabolic acidosis |Aspirin or Salicylates toxicity |Ethylene glycol toxicity |Ethanol toxicity |Methanol toxicity |Ricin toxicity |Carbon Tetrachloride Toxicity |Renal Tubular Acidosis |Lactic acidosis |Iron Toxicity |Tricyclic Antidepressant Toxicity |Opiate Toxicity |Carbon monoxide Toxicity |Benzodiazepine Toxicity |Paracetamol (Acetaminophen) toxicity |Amphetamine toxicity |Beta Blocker toxicity |Calcium channel blockers toxicity |Cannabis toxicity |Cyanide toxicity |Digoxin Toxicity |Lithium Toxicity |NSAIDS Toxicity |Ecstasy toxicity |Paraquat toxicity |Quinine toxicity |SSRI Toxicity |Theophylline Toxicity |Organophosphate (OP) Toxicity |Toxin elimination by dialysis |Drug Toxicity with Specific Antidotes

Glucagon is the conventional antidote for beta-blocker overdose, the most likely cause of this patient's presentation. It reverses hypoglycaemia and improves myocardial contractility and heart rate by stimulating the production of cyclic AMP, thereby enhancing cardiac output and counteracting the effects of beta-blockade.

About Beta Blocker Toxicity

• Beta-blocker toxicity can lead to significant clinical effects, especially in cardiovascular, respiratory, CNS, and metabolic systems.
• Commonly encountered beta-blockers include propranolol, atenolol, metoprolol, and carvedilol.
• Overdose may occur due to accidental ingestion, deliberate self-harm, or interactions with other medications.

Clinical Features

• Cardiovascular Effects:
  • Bradycardia (slow heart rate) is often the most prominent sign.
  • Hypotension (low blood pressure) may occur due to reduced cardiac output.
  • AV block and other arrhythmias, including junctional rhythms and ventricular ectopy, are common.
  • Cardiogenic shock can develop in severe cases, necessitating urgent intervention.
  • Signs of poor perfusion, such as cool extremities and altered mental status, may also be present.
• Respiratory Effects:
  • Bronchospasm, particularly with non-selective beta-blockers, can lead to wheezing and difficulty breathing.
  • Respiratory depression may occur, especially in patients with underlying lung conditions or who are also using CNS depressants.
• Central Nervous System Effects:
  • Lethargy and dizziness are common early signs.
  • Seizures can occur, particularly in severe cases or with polysubstance use.
  • Coma may result in advanced toxicity, necessitating intensive monitoring and management.
• Metabolic Effects:
  • Hypoglycemia is especially concerning in children, who may present with irritability and altered consciousness.
  • Hyperkalemia can develop due to impaired renal function and cellular shifts caused by beta-blocker effects on potassium channels.

Management

• Immediate Actions:
  • Perform ABC (Airway, Breathing, Circulation) assessment to stabilize the patient.
  • Continuous cardiac monitoring is essential due to the risk of arrhythmias.
  • Provide supportive IV fluid therapy with 0.9% Saline to maintain blood pressure and volume.
• Bradycardia: Administer Atropine 0.5 mg (500 mcg) IV, repeating up to a total of 3 mg IV if necessary; consider temporary pacing if bradycardia persists.
• Glucagon: Administer a 2-10 mg IV bolus over 2-5 minutes with 5% Dextrose, followed by a continuous infusion of 2-10 mg/hr as needed.
  • Note: Monitor for side effects, which may include hypocalcemia and hyperglycemia. Glucagon can be effective in both beta-blocker and calcium channel blocker toxicity due to its inotropic effects.
• Alternative Therapy: Consider using Enoximone 5–20 mcg/kg/min, especially in cases where beta-blockade has resulted in significant hemodynamic instability.
• High-Dose Insulin Euglycemia (HIE) Therapy: Consultation with a poison specialist or intensive care unit is advised for management.
  • Initiate treatment with a bolus of 1 U/kg of regular insulin and administer 0.5 g/kg dextrose IV, followed by 10% Dextrose and potassium as per local guidelines.
  • Monitor blood glucose and electrolytes closely during treatment.
• Inotropes: Dobutamine may be employed to enhance cardiac output if the patient remains hypotensive despite other interventions. Intra-aortic balloon pumping may also be considered in critical cases.
• Bronchospasm: Administer Salbutamol (Albuterol in the US) nebulizers to relieve bronchospastic symptoms; monitor respiratory status closely.

References

• Beta Blocker Toxicity
• Enoximone in ICU