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Syndrome of Inappropriate Antidiuretic Hormone (SIADH) CDI Scenario

April 2023

H&P: 67-year-old male sent to ER from Rehab with altered mental status and lethargy. Has been complaining of headache for last 24 hours. Patient is currently oriented to self and is unable to participate in exam. CT Scan completed at Rehab with no change to ICH, no midline shift or brain compression. Pt is hyponatremic with a sodium of 123 mEq/L.

PMH: MVA with ICH 4 weeks ago, HTN, DM 2, COPD on 2 LPM via NC home oxygen, Complete heart block with PPM placement, Chronic Diastolic CHF, CKD stage 3a

Home medications: Keppra 500 mg PO BID, Losartan 50 mg PO daily, Metoprolol 100 mg PO daily, Lasix 40 mg PO daily, Metformin 500 mg PO BID, Advair inhaler BID, Albuterol inhaler PRN

Vitals: Temp 98.4, B/P 135/82, RR 21, HR 60, Pulse ox 92% on 2 LPM via NC, 89% on room air

Physical Exam: Oriented x 1 to self, lethargic, complaining of headache, skin turgor normal, no extremity edema noted, euvolemic, hypoxia on room air

Labs: Serum Sodium 118, Serum Osmolality 205, Creatinine 2.1 (baseline 2.2), GFR 49, BNP 105, Glucose 146, Urine sodium 58, Urine Osmolality 545, Thyroid function tests and ACTH stimulation test WNL

Sodium Day 2 = 121, day 3 = 125, day 4 = 127, day 5 = 124, day 6 = 130, day 7 = 135, day 8 = 136

Radiology: MRI with reduction in size of ICH, Renal US with normal kidneys, ureters, and bladder

Treatment: Renal & endocrine consult, infusion of 3% saline for 24 hrs, fluid restriction 1L, Salt tabs 1g PO TID, Renal US, Thyroid & Adrenal testing, daily labs, Endocrine – started Tolvaptan 15 mg po daily, fluid restriction lifted, d/c Salt tabs

Discharge Summary: Hyponatremia – resolved, altered mental status – resolved, currently A&O x 3, CKD 3a, Chronic diastolic congestive heart failure – euvolemic, COPD – remains on 2 LPM NC due to hypoxia, History of ICH 4 weeks ago, HTN, DM2

Discharge Medication: D/C to Rehab, Tolvaptan 15 mg po daily, Endocrine appt in 2 weeks, lab & LFT testing prior to appt.

Are there query opportunities based on the scenario stated above?

Discussion: Pt with recent ICH admitted with hyponatremia, AMS, and lethargy. Low serum sodium, elevated serum osmolality, elevated urine sodium and osmolality, normal thyroid and adrenal function tests.

  • 3% Sodium infusion for 24 hours
  • Consult to Renal and Endocrine
  • Tolvaptan 15 mg po daily

UASI Recommends:

  • Query for the etiology of Hyponatremia (due to SIADH versus other etiology)
  • Query for Altered Mental Status with Metabolic Encephalopathy versus Altered Mental Status without Metabolic Encephalopathy
  • Query for Chronic Hypoxic Respiratory Failure versus Hypoxia without Respiratory Failure

Documentation without clarification:

Principal Diagnosis: Hyponatremia (E87.1)

Secondary Diagnosis: HTN/CHF/CKD (I13.0), Chronic Diastolic CHF (I50.32), COPD (J44.9), CKD 3a (N18.31), DM2 CKD (E11.22) Complete Heart Block (I44.2) Presence of Pacemaker (Z95.0)

Working DRG: Miscellaneous disorders of nutrition, metabolism, fluids & electrolytes without MCC – DRG 641

RW: 0.7542 GMLOS: 2.60 SOI/ROM: 2/2

Documentation with clarification:

Principal Diagnosis: SIADH (E22.2)

Secondary Diagnosis: Metabolic Encephalopathy (G93.41), Chronic hypoxic respiratory failure (J96.11), HTN/CHF/CKD (I13.0), Chronic Diastolic CHF (I50.32), COPD (J44.9), CKD 3a (N18.31), DM2 CKD (E11.22) Complete Heart Block (I44.2) Presence of Pacemaker (Z95.0)

Working DRG: Endocrine disorders with MCC – DRG 643

RW: 1.6677 GMLOS: 5.00 SOI/ROM: 3/3

CDI Educational Tips:

Coding considerations:

  • SIADH develops when too much antidiuretic hormone is released by the pituitary gland inappropriately, causing the body to retain fluid and lower blood sodium levels by dilution
  • The SIADH presenting symptoms are hyponatremia and hypo-osmolality
  • Conditions leading to SIADH include the following:
    • Central nervous system disturbances such as stroke, hemorrhage, infection, and trauma which cause an excessive release of ADH resulting in decreased sodium level and possible fluid overload
    • Cancer including small cell lung cancer, extrapulmonary small cell carcinomas, head and neck cancers, and olfactory neuroblastomas
    • Certain medications including: SSRIs, Ecstasy, NSAIDs, opiates, interferons, methotrexate, vincristine, vinblastine, ciprofloxacin, haloperidol, and high dose imatinib
    • Surgery which is thought to be mediated by pain afferents
    • Pulmonary disease including pneumonia, atelectasis, asthma, pneumothorax, and acute respiratory failure
    • Hormone deficiencies including hypopituitarism and hypothyroidism
    • Exogenous hormone administration, including vasopressin, desmopressin, and oxytocin
    • Human Immunodeficiency Virus infection
    • Hereditary SIADH
  • SIADH Evaluation is based on the Schwartz and Bartter Clinical Criterion:
    • Serum sodium < 135 mEq/L o Serum osmolality < 275 mOsm/kg o Urine sodium > 40 mEq/L
    • Urine osmolality > 100 mOsm/kg
    • The absence of clinical evidence of volume depletion – skin turgor normal, B/P WNL
    • The absence of other causes of hyponatremia – adrenal insufficiency, hypothyroidism, cardiac failure, pituitary insufficiency, renal disease with salt wastage, hepatic disease, drugs that impair renal water excretion.
    • Correction of hyponatremia by fluid restriction
  • Code only the SIADH, not the hyponatremia since it is integral to the disease process
  • Must rule out adrenal insufficiency and hypothyroidism before diagnosing with SIADH

This is a short synopsis of a possible patient record and is not intended to be all inclusive. This is for educational purposes only and not intended to replace your institutional guidelines.