Table 2.
Summary of recommendations for approaches to diagnosis of hyponatremia by included guidance documents
| 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 | +/– | |||||||||
[Na], Serum sodium concentration; +, always; +/–, If clinically indicated/sometimes useful.
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].