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Table 2 Summary of recommendations for approaches to diagnosis of hyponatremia by included guidance documents

From: Diagnosis and treatment of hyponatremia: a systematic review of clinical practice guidelines and consensus statements

 

Guideline Organization/Society

 

Criteria/Categories

NIV [16]

NHS [17]

GAIN [22]

AEEH [23]

EHN [25]

ERBP/ESE/ESICM [20]

UF [18]

HEP [19]

RCHM [21]

EAH-ICD [24]

Threshold workup [Na]

<135 mmol/L

<135 mmol/L

<135 mmol/L

<130 mmol/L

<135 mmol/L

<135 mmol/L

<131 mmol/L

<135 mmol/L

<135 mmol/L

 

Confirming hypotonic hyponatremia

Serum osmolality <275 mOsm/kg

Plasma osmolality <280 mOsm/kg

Serum osmolality <275 mOsm/kg

 

Plasma osmolality <275 mOsm/kg

Serum osmolality <275 mOsm/kg

Serum osmolality <285 mOsm/kg

Plasma osmolality <280 mOsm/kg

Serum osmolality threshold not stated

 

How to classify hypotonic hyponatremia to aid identification of underlying cause

          

Volume status/hydration state/extracellular fluid status

Clinical evaluation

Physical examination/clinical signs of dehydration or edema

Physical examination/clinical signs of dehydration or edema

 

Physical examination/clinical signs of low circulating volume

Physical examination/clinical signs of dehydration or edema

Physical examination/laboratory measurements

Physical examination/laboratory measurements

To assess but method not stated

 

Urinary [Na]/Threshold

30 mmol/L

Spot urine: 20–30 mmol/L

15 mmol/L

 

40 mmol/L

30 mmol/L

25 mmol/L

Spot urine: 20–30 mmol/L

No threshold stated

 

Urinary osmolality/Threshold

100 mOsm/kg

100 mOsm/kg

100 mOsm/kg

 

100 mOsm/kg

100 mOsm/kg

100 mOsm/kg

100 mOsm/kg

No threshold stated

 

How to identify the underlying disorder

          

History

 

Medications

Medications

  

Diuretic use

    
  

Fluid intake

Recently prescribed intravenous fluids

       
  

Nocturnal polyuria

Vomiting/diarrhea

       

Lab tests

          

Serum potassium concentration

+

+

      

+

 

Serum chloride concentration

 

+

      

+

 

Serum urea concentration

+/–

+

    

+/–

+/–

+

 

Serum creatinine concentration

+

+

    

+/–

+/–

+

 

Serum glucose concentration

+

+

+/–

  

+

  

+

 

Urinary potassium concentration

+

     

+

   

Renal tests

  

+

       

Liver tests

  

+

   

+/–

   

Urinary protein

 

+/–

        

Thyroid function tests

+/–

+/–

+/–

   

+/–

   

Adrenal function tests

+/–

+/–

+/–

   

+/–

   

Serum protein electrophoresis

 

+/–

        

Urine protein electrophoresis

 

+/–

        

Fractional sodium excretion

+/–

         

Serum uric acid concentration

+/–

+/–

    

+

+/–

  

Fractional uric acid concentration

+/–

         

Fractional excretion urea

+/–

         

Urinary chloride concentration

+/–

     

+

+/–

  

Molar weight urine

+/–

         

Serum bicarbonate concentration

      

+/–

   

Hematocrit

      

+/–

   
  1. [Na], Serum sodium concentration; +, always; +/–, If clinically indicated/sometimes useful.
  2. NIV, Nederlandse Internisten Vereniging [16]; NHS, National Health Service [17]; GAIN, Guidelines and Audit Implementation Network [22]; AEEH, La Asociación Española para el Estudio del Hígado [23]; EHN, European Hyponatremia Network [25]; ERBP, European Renal Best Practice; ESE, European Society of Endocrinology; ESICM, European Society of Intensive Care Medicine [20]; UF, University of Florida [18]; HEP, Hyponatremia Expert Panel [19]; RCH Melbourne, the Royal Children’s Hospital Melbourne [21]; EAH-ICD, International Exercise-Associated Hyponatremia Consensus Development Conference [24].
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BMC Medicine

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