What is the management for an elderly patient with a history of cardiovascular disease, presenting with hyponatremia and bradycardia, on metoprolol (beta blocker), who is alert and comfortable with slight giddiness?

Management of Hyponatremia and Bradycardia in an Elderly Patient on Metoprolol

Immediate Priority: Address the Symptomatic Bradycardia First

Hold the metoprolol immediately and do not administer the next dose. The patient has symptomatic bradycardia (37 bpm with giddiness), which represents an absolute contraindication to continued beta-blocker therapy 1. The European Heart Journal identifies symptomatic bradycardia (heart rate <50-60 bpm with symptoms like dizziness or lightheadedness) as a contraindication to beta-blocker therapy 1.

Critical Assessment Before Any Intervention

• Check blood pressure immediately - if systolic BP <100 mmHg with symptoms, this compounds the urgency 1
• Obtain a 12-lead ECG to rule out high-grade AV block (second or third-degree), which would be an absolute contraindication to restarting metoprolol 1
• Assess for signs of hypoperfusion: altered mental status beyond the giddiness, oliguria, cool extremities 1
• Rule out other causes of bradycardia: hypothyroidism, increased intracranial pressure, infection, or drug interactions with other rate-lowering agents (digoxin, diltiazem, verapamil, amiodarone) 1

If Severe Hemodynamic Compromise Develops

• Administer atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg total) as first-line therapy for acute symptomatic bradycardia while arranging definitive management 1
• Have transcutaneous pacing readily available if atropine fails 1

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Management of the Hyponatremia (Sodium 125 mEq/L)

Classification and Symptom Assessment

This patient has moderate hyponatremia (sodium 125 mEq/L, defined as 125-129 mEq/L) 2. The "slight giddiness" could represent either the bradycardia or mild hyponatremic symptoms (nausea, weakness, headache, mild neurocognitive deficits are typical) 2. Importantly, the patient is alert and comfortable, indicating this is not severely symptomatic hyponatremia requiring emergency hypertonic saline 3.

Determine Volume Status

Assess whether the patient is hypovolemic, euvolemic, or hypervolemic 3:

• Check for orthostatic hypotension (suggests hypovolemia)
• Examine for edema, jugular venous distension, pulmonary rales (suggests hypervolemia from heart failure)
• Order urine sodium and osmolality to help differentiate causes 2

Likely Etiology in This Patient

Metoprolol is not a direct cause of hyponatremia, but polypharmacy and cardiovascular medications increase risk 4. In elderly patients on metoprolol, hyponatremia is commonly associated with:

• Diuretics (especially thiazides) - if the patient is taking these, they are strongly associated with hyponatremia (OR: 1.83) 4
• RAAS inhibitors (ACE inhibitors/ARBs) - associated with hyponatremia (OR: 1.71) 4
• Antidepressants (SSRIs like escitalopram OR: 1.82, trazodone OR: 2.27) 4
• Syndrome of inappropriate antidiuresis (SIAD) - common in elderly 3

Treatment Strategy Based on Volume Status

For euvolemic hyponatremia (most likely SIAD):

• Restrict free water to 800-1000 mL/day 2
• Consider salt tablets (1-2 grams three times daily) 2
• Urea (15-30 grams/day) or vaptans can be effective but have adverse effects (poor palatability with urea; overly rapid correction risk with vaptans) 3

For hypovolemic hyponatremia:

• Administer normal saline (0.9% NaCl) infusions 2
• This will correct both volume and sodium 2

For hypervolemic hyponatremia (if heart failure present):

• Treat underlying heart failure with diuretics and GDMT optimization 3
• Restrict free water 2
• Vaptans may be considered for heart failure-related hyponatremia 3

Critical Correction Limits

Do NOT correct sodium faster than 4-6 mEq/L in the first 1-2 hours, and no more than 10 mEq/L in 24 hours 3. Overly rapid correction can cause osmotic demyelination syndrome, resulting in parkinsonism, quadriparesis, or death 3. Use calculators to guide fluid replacement 2.

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Management of the Metoprolol

Do Not Abruptly Discontinue

Never abruptly stop metoprolol completely - this can cause severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias, with a 50% mortality rate in one study 1, 5. Beta-blocker withdrawal is associated with a 2.7-fold increased risk of 1-year mortality 1.

Recommended Strategy

Once heart rate improves above 50-55 bpm and symptoms resolve:

• Restart metoprolol at 50% of the previous dose (e.g., if on 25 mg twice daily, restart at 12.5 mg twice daily) 1
• Monitor heart rate and blood pressure closely - check every 4-6 hours initially 1
• Titrate slowly over weeks based on heart rate response, targeting resting heart rate of 50-60 bpm 1
• Maintain systolic BP >100 mmHg 1

Alternative Consideration

If bradycardia recurs or patient cannot tolerate metoprolol restart:

• Consider switching to a rate-neutral alternative if the indication is hypertension alone (not heart failure or post-MI) 6
• For rate control in atrial fibrillation, consider diltiazem 120-360 mg daily as an alternative 1

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Monitoring Plan

Short-term (First 24-48 Hours)

• Check sodium every 4-6 hours until stable and correcting appropriately 2
• Monitor heart rate and blood pressure every 4-6 hours 1
• Assess mental status frequently for worsening confusion or new neurological symptoms 3
• Watch for signs of worsening heart failure, angina, or ischemia after holding metoprolol 1

Medium-term (1-2 Weeks)

• Recheck sodium after 1 week to ensure stability 7
• Reassess heart rate and blood pressure at 1-2 week follow-up after metoprolol dose adjustment 1
• Review all medications for potential contributors to hyponatremia (diuretics, RAAS inhibitors, antidepressants, opioids) 4, 7

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Common Pitfalls to Avoid

• Do not give IV metoprolol in this setting - the patient has symptomatic bradycardia, which is an absolute contraindication 1
• Do not correct sodium too rapidly - this causes osmotic demyelination 3
• Do not completely stop metoprolol without a plan to restart - withdrawal increases mortality 1
• Do not assume giddiness is only from hyponatremia - symptomatic bradycardia is the more immediate threat 1
• Do not delay treatment while pursuing diagnosis - address the symptomatic bradycardia first 2
• Do not forget to check for drug interactions - multiple medications causing bradycardia (digoxin, calcium channel blockers, amiodarone) compound the risk 1