What is the treatment for an adult patient with a history of bipolar disorder and potential renal disease, presenting with bradycardia due to lithium toxicity?

Treatment of Bradycardia from Lithium Toxicity

Immediately discontinue lithium and initiate aggressive supportive care with intravenous fluids, atropine for symptomatic bradycardia, and hemodialysis for severe toxicity, while preparing for temporary pacing if pharmacologic measures fail. 1, 2

Immediate Management Steps

Discontinue Lithium and Assess Severity

• Stop lithium immediately upon recognition of toxicity, as this is the first and foremost intervention 1, 3
• Measure serum lithium level urgently (therapeutic range 0.4-1.0 mEq/L; toxicity typically >1.5 mEq/L, though cardiac effects can occur at therapeutic levels) 4, 3
• Assess for hemodynamic compromise: hypotension, altered mental status, and degree of bradycardia 2
• Obtain ECG to evaluate for conduction abnormalities including sinus bradycardia, sinoatrial block, PR prolongation, and QT changes 4

Fluid Resuscitation and Electrolyte Management

• Administer aggressive intravenous fluid therapy as the cornerstone of initial treatment, which enhances renal lithium elimination and corrects dehydration that often precipitates toxicity 1, 5, 2
• Correct electrolyte imbalances, particularly hyperkalemia, hypokalemia, and hypoglycemia, which can worsen bradycardia 6
• Monitor renal function closely, as acute kidney injury commonly accompanies lithium toxicity and impairs lithium clearance 2, 7

Pharmacologic Treatment of Bradycardia

Atropine as First-Line Agent

• Administer atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg total) for symptomatic bradycardia with hemodynamic compromise 6, 8
• Atropine is reasonable to increase sinus rate in patients with sinus node dysfunction from reversible causes like lithium toxicity 6
• Avoid doses <0.5 mg as paradoxical slowing may occur 8

Alternative Pharmacologic Agents

• Consider inotropic support with dopamine or dobutamine if bradycardia persists despite atropine, particularly in patients with hypotension 2
• Beta agonists (isoproterenol, dopamine, dobutamine, or epinephrine) may be considered in patients at low likelihood of coronary ischemia, though use cautiously in elderly patients 6

Temporary Cardiac Pacing

Indications for Pacing

• Initiate transcutaneous pacing if bradycardia is unresponsive to atropine and causing hemodynamic instability 8, 2
• Consider temporary transvenous pacemaker insertion for severe, persistent sinus bradycardia despite pharmacologic interventions 5
• Pacing may be necessary during the acute phase while lithium levels decline and cardiac function recovers 5, 2

Enhanced Elimination Strategies

Hemodialysis Indications

• Perform hemodialysis urgently for severe lithium toxicity, particularly when serum lithium >3.0 mEq/L, severe neurological symptoms, cardiac arrest, or refractory bradycardia are present 1, 5, 7
• Hemodialysis is the most effective and rapid means of removing lithium from severely toxic patients 1
• Continue dialysis until lithium levels are in safe range and clinical improvement is evident 5, 7

Adjunctive Measures to Enhance Excretion

• Urea, mannitol, and aminophylline can produce significant increases in lithium excretion, though hemodialysis remains superior for severe cases 1
• Maintain adequate kidney function through fluid resuscitation to optimize lithium clearance 1

Special Considerations in This Population

Bipolar Disorder and Renal Disease Context

• Assess thyroid function immediately in patients with suspected lithium toxicity, as thyrotoxicosis increases tubular reabsorption of lithium and can precipitate toxicity even after lithium cessation 5
• Pre-existing renal disease dramatically increases risk of lithium accumulation and toxicity 2, 7
• Dehydration is a common precipitant in this population and must be aggressively corrected 5, 7

Monitoring During Recovery

• Cardiac manifestations of lithium toxicity are typically reversible upon discontinuation and normalization of lithium levels 4, 3
• Normal sinus rhythm usually restores within 3-7 days after lithium discontinuation and supportive care 3
• Continue cardiac monitoring until bradycardia resolves and lithium levels normalize 2

Critical Pitfalls to Avoid

• Do not delay hemodialysis in patients with severe toxicity (lithium >3.0 mEq/L), cardiac arrest, or profound neurological symptoms 5, 7
• Do not assume therapeutic lithium levels exclude toxicity, as cardiac effects can occur within therapeutic range, particularly with chronic use 3
• Do not overlook precipitating factors including dehydration, renal insufficiency, thyroid dysfunction, and drug interactions that impair lithium clearance 5, 7
• Do not use atropine in heart transplant patients without evidence of autonomic reinnervation 6
• Permanent pacemaker insertion is rarely needed, as lithium-induced bradycardia is typically reversible; reserve this only for irreversible sinus node dysfunction requiring long-term lithium continuation 3

Prognosis and Long-Term Management

• Most patients recover completely with appropriate supportive care and lithium discontinuation 4, 3
• Neurological recovery may lag behind cardiac recovery, with gradual improvement over weeks 5
• Re-evaluate the need for lithium therapy after recovery, considering alternative mood stabilizers if toxicity was severe 3
• If lithium must be continued, ensure close monitoring of serum levels, renal function, thyroid function, and cardiac rhythm 7