Beta blockers

β1

• Heart
• Kidneys
  • β1 blockade of the juxtaglomerular cells → ↓ renin release → ↓ angiotensin II conversion → ↓ H₂O resorption → ↓ BP t

Tip

• Beta-1 agonists can result in increased renin release → hypokalemia
• Beta-2 agonists can increase the activity of the Na-K-ATPase pump → hypokalemia (transient)

Beta blocker overdose

Clinical features

• Clinical features of CV drug poisoning: typically bradycardia, hypotension, and CNS depression
• Other features
  • Delirium
  • Respiratory depression
  • Seizures (typically seen with propranolol)
  • Bronchospasm (rare)

Management

• Hypotension: IV fluid bolus
• Symptomatic bradycardia: atropine
• High-dose glucagon therapy
  • Glucagon activates adenylate cyclase, leading to increased intracellular cAMP during depolarization, which improves cardiac contractility and heart rate.