Beta Blocker Overdose

Clinical Manifestations: Mainly hypotension and bradycardia.  On EKG, can see PR prolongation leading ot AV block, and sometimes QRS prolongation (with certain beta blockers like sotalol).  Can also see mild hyperkalemia and hypoglycemia. 
Ddx includes overdose of calcium channel blockers, digoxin, and cholinergic agents.
Management:

• ABCs first obviously
• IVF boluses as tolerated
• Remember your ACLS Bradycardia Algorhithm, which emphasizes treatment for symptomatic bradycardia first with atropine (0.5 mg at a time, up to max 3 g); if ineffective, follow with transcutaneous pacing +/- infusions of dopamine or epinephrine.

Medical Therapy for Beta-Blocker Toxicity:
1.  Atropine – 0.5 mg pushes at a time, q3-5 minutes, maximum of 3 g.
Acts at the AV node – will not work for block at or below the bundle of His.  Also does not work in transplanted hearts (as they lack vagal innervation).      
Side effects: Anticholinergic effects = 1) CNS effects, 2) GI – decreased saliva, nausea, vomiting, ileus, 3) GU – urinary retention, 4) CV – tachycardia (obviously) and arrhythmias, 5) Eyes – blurry vision
2.  Glucagon – 5 mg bolus over 1 minute, can repeat 10-15 minutes later.  If positive response, can start an infusion at 2-5 mg/hour.
Activates adenylate cyclase to raise cAMP levels, which increases intracellular Ca releat.  This increases contractility and possibly heart rate.  Even though this is considered a 1st-line “antidote” there is actually limited data to support this.  Main side effect = nausea/vomiting.
3.  IV calcium – can give CaCl (if have central line) or Ca Gluconate (if peripheral line).  CaCl has 3-5x more calcium than Ca gluconate, but is sclerosing to veins and hence must be given through central lines.  Acts to increase contractility, does not raise HR.  Careful of causing hypercalcemia!
4.  Catecholamines – first line are Epinephrine or Dopamine, due to both inotropic effect and vasoconstriction.  Avoid Isoproterenol as this can cause peripheral vasodilation and thus hypotension; avoid dobutamine alone for this same reason.  Norepinephrine is not unreasonable but careful due to the predominantly vasoconstricting effects without inotropy, which due to increased afterload, can negatively affect cardiac output.

*Note that the treatment for Calcium Channel Blocker toxicity is basically the same, and both Calcium and Glucagon can be given in both situations!*

(Chanue Rhee MD, 3/24/11)