Hyponatremia secondary to SIADH and coexisting LV systolic dysfunction

• 77-year-old woman who had quit smoking after 33 years presented with worsening shortness of breath
  • Patient also reported fatigue
• At the time of presentation, patient had recurrence of lung cancer and breast cancer
• The following was found when the patient was admitted to the hospital:
  • Serum [Na⁺]: 127 mEq/L
  • New onset severe LV systolic dysfunction

LV = left ventricle

Medical History

• COPD
• Lung Cancer
  • Left upper lobe
  • Status post wedge resection
  • Radiation and chemotherapy
  • Now with recurrence
• Colon Cancer
• Diverticulosis
• Paroxysmal atrial fibrillation
• Breast Cancer
  • Left breast
  • Status post mastectomy
  • Now with recurrence

Surgical History

• Left upper lobe resection
• Appendectomy
• Partial colectomy
• Cholecystectomy
• Vocal cord transplant
• Left mastectomy

The patient was on the following medications at the time of admission:

• Cetirizine 10 mg qd
• Amiodarone 200 mg qd
• Ipratropium bromide/albuterol inhaled as needed
• Albuterol 2 puffs bid
• Docusate sodium 100 mg qd
• Tiotropium inhaled one puff qd
• Methylcellulose 2 g qd
• Multivitamin qd
• Lorazepam 0.5 mg bid prn
• Letrozole 2.5 mg qhs
• Fluticasone propionate/salmeterol inhaled 500/50 one puff bid
• Fluticasone propionate nasal 2 sprays qd
• Doxycycline 100 mg bid x5 days

The patient appeared in no apparent respiratory distress but did feel winded. Patient was cooperative and communicated clearly.

Laboratory Data:

• Serum [Na⁺]: 127 mEq/L
• Urine osmolality: 245 mOsm/Kg
• Serum uric acid: 1.7 mg/dL
• TSH: WNL

Physical Exam:

• Vital Signs
  • BP: 116/65 mm Hg
  • HR: 102 bpm (regular)
  • RR: 18
  • Temperature:97.5^°C
• HEENT
  • Anicteric sclerae
  • Pink conjunctivae
  • Dry mucous membranes
  • PERRLA
  • EOMI
  • No nystagmus noted
• Neck
  • No JVD
  • No carotid bruit
• Chest
  • Decreased air entry
  • Minimal expiratory wheeze anteriorly
• Heart
  • S1, S2 heard
  • RRR
• Abdomen
  • Benign
• Extremities
  • No cyanosis
  • No clubbing
  • No edema

BP = blood pressure; EOMI = extraocular movements intact; HEENT = head, eyes, ears, nose, and throat; HR = heart rate; JVD = jugular venous distension; PERRLA = pupils equal, round, reactive to light and accommodation; RR = respiratory rate; RRR = regular rate and rhythm; TSH = thyroid stimulating hormone; WNL = within normal limits

• Symptomatic dilutional hyponatremia from SIADH (possibly secondary to lung cancer) complicated by cardiac congestion
  • Hypouricemia and absence of obvious signs of volume overload were more consistent with SIADH
  • Paitent was already on adequate steroids, so adrenal insufficiency was unlikely
  • TSH was normal, excluding hypothyroidism as an etiology

• Patient was initially treated with fluid restriction and loop diuretic
• Serum [Na⁺] decreased initially from 127 to 126 mEq/L (day 2) and remained steady to day 3

• Serum [Na⁺] of 126 mEq/L (resisted correction with fluid restriction) and patient remained symptomatic with fatigue
• Diagnosis of dilutional hyponatremia, likely secondary to SIADH

Too-rapid correction of hyponatremia (e.g., >12 mEq/L/24 hours) can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death.

Subjects with SIADH may be at greater risk for too-rapid correction of serum [Na⁺].

• Initial management of the patient’s hyponatremia included fluid restriction and the use of loop diuretics
• This strategy was continued for 2 days, but as shown, did not result in an increase in serum [Na⁺]
• On day 3 the decision was made to discontinue fluid restriction and to initiate SAMSCA (15 mg/day)
• The next day, the patient’s serum [Na⁺] rose 6 mEq/L
• On day 5, SAMSCA was discontinued and the patient’s serum [Na⁺] normalized over the remainder of the hospital stay

Do not administer SAMSCA for more than 30 days to minimize the risk of liver injury.

• Patient with dilutional hyponatremia likely secondary to SIADH and coexisting LV systolic dysfunction
• Serum [Na⁺] at admission was 127 mEq/L
• Following 2 days of fluid restriction and loop diuretics, serum [Na⁺] was 126 mEq/L
• Fluid restriction was discontinued, and SAMSCA was started
  • The next day, serum [Na⁺] increased 6 mEq/L
  • On day 5, SAMSCA was discontinued, and the patient’s serum [Na⁺] normalized over the course of her hospital stay

Too-rapid correction of hyponatremia (e.g., >12 mEq/L/24 hours) can cause serious neurologic sequelae, including osmotic demyelination syndrome (ODS)

Avoid fluid restriction during the first 24 hours of therapy

Do not administer SAMSCA for more than 30 days to minimize the risk of liver injury.