Hyponatremia resident survival guide

Hyponatremia Resident Survival Guide
Overview
Causes
FIRE
Diagnosis
Treatment
Do's
Don'ts

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Iqra Qamar M.D.[2] Priyamvada Singh, M.D. [3]Vidit Bhargava, M.B.B.S [4]

Overview

Hyponatremia is defined as a serum sodium concentration < 135 mEq/L.

Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated. Severe hyponatremia ( <115 mEq/L) is by itself life threatening and should be treated as such irrespective of the cause.

Common Causes

Hypovolemic hyponatremia:

• Cerebral salt wasting syndrome
• Adrenal failure
• Thiazide diuretics
• Vomiting or diarrhea treated with free water replacement

Euvolemic hyponatremia:

• SIADH
• Primary polydipsia
• Exercise associated hyponatremia
• Glucocorticoid deficiency
• Hypothyroidism
• Nephrogenic syndrome of inappropriate antidiuresis
• Low sodium intake

Hypervolemic hyponatremia:

• Acute kidney injury
• Cirrhosis
• Heart failure

Causes of Hyponatremia based upon Serum Osmolality:

Serum Osmolality	Etiology
Hypertonic Hyponatremia	Hyperglycemia
	Mannitol
	Glycerol
	Sorbitol
Isotonic Hyponatremia	Lab/blood draw error
	Hyperparaproteinemia
	Hyperlipidemia
	Post TURP (bladder irrigation with osmotic solutions)
Hypotonic Hyponatremia	Etiology depends upon volume status (Hypervolemic/ Euvolemic/ Hypovolemic

Classification

Hyponatremia is defined as serum sodium less than 135 mEq/L (mmol/L).There are different classifications for hyponatremia based on duration, severity, volume status and ADH level.

Hyponatremia is classified based on serum sodium level to :

• Mild : Serum sodium 130– 135 mmol/L
• Moderate:  Serum sodium ≤125–129 mmol/L
• Severe: Serum sodium <124 mmol/L

Classification based on duration :

• Hyperacute: Develops in a few hours, excess water intake, impaired water excretion, runners, users of the recreational drug (Ecstasy)

• Acute: Rapid onset <48 hours, surgeries, colonoscopy preparation, polydipsia, diuretics
• Chronic: Gradual onset >48 hours, caused by chronic disease ( including cardiac, renal, hepatic and other conditions)

Classification based on ADH level :

• ↑ ADH: Volume depletion (GI loss, Renal loss) , decreased perfusion ( CHF, Cirrhosis), increased ADH secretion, reset osmostat

• ↓ ADH: Primary polydipsia, ↓ dietary solute intake, advanced renal failure

According to volume status :

Volume status	Sodium status	True volume depletion : GI loss, Renal loss, Insensible loss
Hypovolemic Hyponatremia	total body water ↓ total body sodium ↓↓
Hypervolemic Hyponatremia	total body water ↑↑ total body sodium ↑	Decreased effective arterial volume : Cirrhosis, Renal disease, CHF
Euvolemic Hyponatremia	total body water ↑ total body sodium ↔	Drugs ,Increased ADH level, Reset osmostat, Low dietary salt intake

Management

Diagnostic Approach

Shown below is an algorithm depicting the diagnostic management of hyponatremia based on Diagnosis, Evaluation, and Treatment of Hyponatremia: Expert Panel Recommendations (2013).

Characterize the symptoms: ❑ Nausea and vomiting ❑ Headache ❑ Confusion ❑ Lethargy, fatigue, loss of appetite ❑ Restlessness and irritability ❑ Muscle weakness, spasms, cramps ❑ Seizures ❑ Decreased consciousness or coma Hyponatremic encephalopathy: (sodium < 115 meq/L) ❑ Altered thirst, hunger, dilated pupils (suggestive of brain stem compression) ❑ Decorticate or decerebrate posturing ❑ Respiratory arrest ❑ Non-cardiogenic pulmonary edema

Examine the patient: ❑ Orthostatic vital signs ❑ Mental status examination (low score) ❑ Jugular venous pressure ↑/↓ ❑ Peripheral edema

Check labs: ❑ Plasma osmolality ❑ Urine osmolality ❑ Urinary sodium concentration ❑ Serum uric acid/creatinine ❑ Thyroid stimulating hormone (TSH) ❑ Serum cortisol level ❑ Serum proteins ❑ Triglyceride ❑ Random blood sugar

Consider alternative diagnosis: ❑ Adrenal crisis ❑ Alcoholism ❑ Hypothyroidism ❑ Pulmonary/cardiogenic edema

❑ Check serum osmolality Serum osmolality (mmol/kg) = (2 x serum sodium concentration) + (serum glucose concentration/18) + (blood urea nitrogen/2.8)

Isotonic hyponatremia (Serum osmolality 280-295 mOsm/kg)

Hypotonic hyponatremia (Serum osmolality < 280 mOsm/kg)

Hypertonic hypernatremia (Serum osmolality > 295 mOsm/kg)

Pseudohyponatremia

Assess volume status

Hyperglycemia Mannitol infusion

Hypovolemia

Euvolemia

Hypervolemia

Urine sodium levels

Urine sodium levels

Urine sodium levels

>20 mEq/L

≤ 20 mEq/L

>20 mEq/L

>20 mEq/L

≤ 20 mEq/L

❑ Cerebral salt wasting syndrome ❑ Adrenal failure ❑ Thiazide like diuretics

❑ Vomiting & diarrhea treated with free water replacement

❑ SIADH ❑ Primary polydipsia ❑ Exercise associated hyponatremia ❑ Nephrogenic syndrome of inappropriate antidiuresis ❑ Glucocorticoid deficiency ❑ Hypothyroidism ❑ Low solute intake

❑ Acute kidney injury

❑ Cirrhosis ❑ Heart failure

Therapeutic Approach

Initial Management

Shown below is an algorithm depicting the initial management of symptomatic hyponatremia based on Diagnosis, Evaluation, and Treatment of Hyponatremia: Expert Panel Recommendations (2013).

Symptomatic hyponatremia

Acute hyponatremia (< 48 hours)

Chronic hyponatremia

Goals of treatment: ❑ Target sodium levels = 125-130 mEq/L ❑ Daily ↑ in sodium levels by 4-6 mmol/L

Goals of treatment: ❑ Target sodium levels = 125-130 mEq/L ❑ Daily ↑ in sodium levels by 4-8 mmol/L if low risk of ODS ❑ Daily ↑ in sodium levels by 4-6 mmol/L if high risk of ODS

Mild to moderate symptoms

Severe symptoms

Mild to moderate symptoms

Severe symptoms

❑ Administer 0.9% NaCl to achieve target sodium levels, or ❑ Administer vaptans

❑ Administer 3% NaCl (100 ml infused over 10 minutes and repeated once if needed) ❑ Shift to 0.9% NaCl/vaptans at sodium levels > 125 mEq/L

❑ Administer 0.9% NaCl to achieve target sodium levels, or ❑ Administer vaptans

❑ Administer 3% NaCl (100 ml infused over 10 minutes and repeated once if needed) ❑ Achieve 1st day target in 1st 6 hours and withhold any more fluids for the day ❑ Shift to 0.9% NaCl/vaptans at sodium levels > 125 mEq/L

Administer vaptans (contraindicated for hypovolemic hyponatremia) ❑ Conivaptan: ❑ Administer IV 20 mg loading dose over 30 minutes, followed by a continuous infusion of 20 mg/day ❑ Maintain a maximal infusion rate 40 mg/day ❑ Treat for 4 days or until the target sodium level is reached ❑ Monitor with sodium levels every 6-8 hours OR ❑ Tolvaptan: (Use only if sodium < 125 mEq/L or pt. symptomatic) ❑ Administer PO 15 mg on the first day ❑ Titrate to 30 mg/60 mg at 24-hour intervals if: Sodium level < 135 mmol/L, or Increase in sodium <5 mmol/L in the last 24 hours ❑ Monitor with sodium levels every 6-8 hours

Additional Management

Shown below is an algorithm depicting the management of symptomatic and asymptomatic hyponatremia based on underlying etiology based on Diagnosis, Evaluation, and Treatment of Hyponatremia: Expert Panel Recommendations (2013).

Etiology based management

Hypovolemia

Euvolemia

Hypervolemia

Urine sodium level > 20 mEq/L

Urine sodium level ≤ 20 mEq/L

Urine sodium level > 20 mEq/L

Urine sodium level > 20 mEq/L

Urine sodium level ≤ 20 mEq/L

Cerebral salt wasting syndrome: ❑ Fluid restriction is not advised Adrenal failure: ❑ Monitor Na+ level frequently ❑ Perform co-syntropin testing ❑ Treat empirically with high dose hyrdocortisone ❑ Administer fludrocortisone once the diagnosis is confirmed Thiazide like diuretics: ❑ Stop thiazide diuretics ❑ Monitor the rate of rise of Na+ ❑ Monitor urine osmolality & volume to detect hypercorrection ❑ Follow K+ levels, as they may drop with therapy

Gastrointestinal losses: ❑ Correct K+ levels as appropriate ❑ Administer bicarbonate if acidosis develops ❑ Start antiemetics and specific therapy as indicated

❑ SIADH: ❑ Restrict water ❑ Do not restrict water if the patient is on vaptans ❑ Use enteral water or D5W to prevent over correction ❑ Consider chronic pharmacotherapy depending on the etiology of SIADH Nephrogenic syndrome of inappropriate antidiuresis: ❑ Similar to SIADH Hypothyroidism: ❑ Treat hyponatremia only when severe ❑ Treat primary etiology Glucocorticoid def.: ❑ Replace glucocorticoids ❑ Monitor sodium levels and urine volume to prevent over correction Exercise associated hyponatremia: ❑ Treat with free water restriction and observation Low solute intake: ❑ Provide proper nutrition of electrolytes and proteins Primary polydipsia: ❑ Restrict water

Acute kidney injury: ❑ Restrict water

Heart failure: ❑ Initiate treatment with fluid restriction ❑ Administer loop diuretics ❑ Consider vaptans Liver cirrhosis: ❑ Use tolvaptan restrictively based on LFT's

ADH: Anti diuretic hormone; SIADH: Syndrome of inappropriate antidiuretic hormone secretion; NaCl: Sodium chloride; LFT: Liver function test;IV: Intravenous; PO: Per oral; ECF:Extra cellular fluid; HPE:History and physical examination; ODS: Osmotic demyelination syndrome

Do's

• Do the following to prevent over correction of sodium levels:

• Replace water losses or administer desmopressin after correction by 6-8 mmol/L during the first 24 hours of therapy.
• Withhold the next dose of vaptans if the correction is >8 mmol/L.
• Consider therapeutic lowering of serum sodium if correction exceeds therapeutic limits.
• Consider administration of high-dose glucocorticoids (eg, dexamethasone, 4 mg every 6 hours) for 24-48 hours following the excessive correction.

• Follow these steps to lower serum sodium, if correction exceeds therapeutic limits:

• Administer desmopressin to prevent further water losses: 2-4 mg every 8 hours parenterally.
• Replace water orally or as 5% dextrose in water intravenously at the rate of 3 mL/kg/h.
• Recheck serum sodium hourly and continue therapy infusion until serum sodium is reduced to goal.

• Initiate vaptans treatment only in hospital setting, so as to regularly monitor serum sodium levels.
• Fluid restrictions:

• Restrict all intake that is consumed by drinking, not just water.
• Aim for a fluid restriction that is 500 mL/d below the 24-hour urine volume.
• Do not restrict sodium or protein intake unless indicated.

• Gastrointestinal losses:

• Measure urine chloride, if vomiting is present to confirm the presence of solute and volume depletion.
• Treat typically as a chronic hyponatremia.

• Thiazide diuretic induced:

• Treat typically as chronic hyponatremia.
• Be vary of rapid correction.
• Serially follow changes in urine osmolality together with urine volume.
• Measure serum sodium every 6 hours to begin with.
• Adjust potassium levels in fluids as needed.

Dont's

• Stop tolvaptan if signs of liver failure develop.
• Vaptans:

• Do not use to treat hypovolemic hyponatremia.
• Do not use in conjunction with other treatments for hyponatremia.
• Do not use immediately after cessation of other treatments for hyponatremia, particularly 3% NaCl.
• Do not use for severe, symptomatic hyponatremia, as 3% NaCl provides a quicker and more certain correction of serum sodium than vaptans.

• Do not use isotonic normal saline as primary therapy for SIADH.

References

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