In an elderly woman with hypertension, hyperlipidemia, a prior episode of hyperosmolar hyponatremia, and anxiety, who is taking hydrochlorothiazide, levothyroxine, lorazepam (Ativan), amlodipine, hydralazine, melatonin, polyethylene glycol (MiraLAX), apixaban, and docusate (Colace) and now has mild hyponatremia (serum sodium 129 mmol/L), what are the appropriate next management steps?

Immediate Management of Mild Hyponatremia in an Elderly Woman on Hydrochlorothiazide

Discontinue hydrochlorothiazide immediately, as thiazide diuretics are the most likely culprit for this patient's sodium of 129 mEq/L, and switch to an alternative antihypertensive agent such as amlodipine (which she is already taking) or add a low-dose ACE inhibitor/ARB. 1

Diagnostic Evaluation

Confirm Thiazide-Induced Hyponatremia

• Thiazide diuretics cause hyponatremia through impaired urinary dilution, renal sodium and potassium loss, stimulation of antidiuretic hormone, and possibly increased thirst 1
• Risk factors present in this patient include elderly age, female sex, and concurrent use of lorazepam (benzodiazepines can impair water excretion) 1
• Thiazide-associated hyponatremia can develop after months or years of use, not just early in treatment 1

Assess Symptom Severity

• Sodium of 129 mEq/L is classified as moderate hyponatremia (125-129 mEq/L) 2
• Evaluate for mild symptoms: nausea, vomiting, weakness, headache, or mild neurocognitive deficits 2
• Check for severe symptoms requiring emergency treatment: delirium, confusion, impaired consciousness, ataxia, or seizures 2

Determine Volume Status

• Assess whether the patient is hypovolemic, euvolemic, or hypervolemic through physical examination (skin turgor, mucous membranes, jugular venous pressure, peripheral edema, orthostatic vital signs) 2
• Obtain serum osmolality, urine sodium, and urine osmolality to confirm hypotonic hyponatremia and guide management 3

Immediate Management Steps

For Asymptomatic or Mildly Symptomatic Patients (Most Likely Scenario)

Step 1: Discontinue Hydrochlorothiazide

• Stop HCTZ immediately—this is the cornerstone of therapy for thiazide-associated hyponatremia 1
• Do not restart thiazide diuretics even after sodium normalizes, as recurrence is common 1

Step 2: Replace Cations

• Check serum potassium and replete if low (thiazides cause both sodium and potassium depletion) 1
• Potassium repletion helps correct hyponatremia by reducing osmotic inactivation of sodium 1

Step 3: Fluid Restriction

• Restrict oral fluid intake to 800-1000 mL/day if euvolemic 2, 1
• If hypovolemic (unlikely given multiple antihypertensives), administer normal saline infusions 2

Step 4: Monitor Sodium Correction

• Recheck serum sodium in 24-48 hours 3
• Target correction rate: 4-6 mEq/L per 24 hours to avoid osmotic demyelination syndrome 2
• Avoid overly rapid correction, especially in chronic hyponatremia (>48 hours duration) 1

For Severely Symptomatic Patients (Sodium <125 mEq/L with Seizures/Altered Mental Status)

• Administer 3% hypertonic saline as 100 mL bolus over 10 minutes, repeatable up to 3 times 2
• Use calculators to guide fluid replacement and avoid overly rapid correction 2
• Transfer to intensive care unit for continuous monitoring 2

Alternative Antihypertensive Management

Replace Hydrochlorothiazide With:

Option 1: Optimize Current Amlodipine

• She is already on amlodipine; consider increasing dose if blood pressure requires better control 4
• Calcium channel blockers do not cause hyponatremia 4

Option 2: Add ACE Inhibitor or ARB

• Start lisinopril 5-10 mg daily or losartan 25-50 mg daily 4
• ACE inhibitors/ARBs are appropriate for elderly patients with hypertension and do not cause hyponatremia 4
• Monitor potassium and creatinine 2-4 weeks after initiation 5

Option 3: Add Chlorthalidone (Only After Sodium Normalizes and If Absolutely Necessary)

• If a diuretic is essential for blood pressure control, chlorthalidone 12.5 mg is preferred over HCTZ 4
• However, avoid reintroducing any thiazide diuretic in this patient given her documented susceptibility to thiazide-induced hyponatremia 1

Additional Considerations

Evaluate for Synergistic Medication Effects

• Lorazepam (Ativan) does not directly cause hyponatremia but may impair water excretion 6
• The combination of thiazide diuretics with medications affecting water balance can have synergistic effects 6
• Consider tapering lorazepam if anxiety can be managed with alternative approaches 6

Rule Out Other Contributing Factors

• Assess for excessive free water intake (common in elderly patients) 2
• Evaluate thyroid function (levothyroxine dose may need adjustment; hypothyroidism causes hyponatremia) 3
• Review for other medications that can cause hyponatremia 2

Monitor for Recurrence

• Recheck sodium weekly for 4 weeks after discontinuing HCTZ 1
• Many patients recover without intervention once the offending agent is stopped 3
• Educate patient to avoid excessive water intake and report symptoms of hyponatremia 2

Critical Pitfalls to Avoid

• Do not continue hydrochlorothiazide while attempting to correct sodium—this will fail 1
• Do not correct sodium too rapidly (>8-10 mEq/L in 24 hours)—risk of osmotic demyelination syndrome is real and devastating 2, 1
• Do not delay treatment while pursuing extensive diagnostic workup if patient is symptomatic 2
• Do not restart thiazide diuretics after sodium normalizes—use alternative antihypertensives 1
• Do not assume all elderly women on thiazides will develop hyponatremia—only a minority are susceptible, but this patient has demonstrated susceptibility 1

Blood Pressure Management During Transition

• Target blood pressure <140/90 mmHg minimum for this elderly patient 4
• She is already on amlodipine, hydralazine, and apixaban (not antihypertensive but indicates cardiovascular risk) 4
• Optimize existing agents before adding new ones 4
• Recheck blood pressure within 2-4 weeks of medication changes 4