Hyponatremia

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Defined  as  serum  sodium  (Na+)  levels  less  than  135mEq/L.  It  can  be  classified  as:  Mild  hyponatremia (130-135 mEq/L), Moderate hyponatremia (125 -129 mEq/L), Severe hyponatremia (<  125mEq/L). 

Clinical presentation 

Clinical signs generally will occur once levels are <125mEq/L. The following are symptoms related to  hyponatremia: 

  • Nausea and vomiting
  • Fatigue
  • Dizziness
  • Headache or confusion
  • Tremulousness or seizures
  • Urine Osmolality
  • Thyroid profile
  • CT brain (suspected cerebral process)
  • CXR (suspected pulmonary 
  • infection/edema – related to renal failure, CCF) 

Non-pharmacological Treatment: Nutritional measures adjusted to patients need 

  • Salt containing foods
  • Rehydration therapy
  • Dietary modification

The  goal  of  acute  management  is  treatment  of  serious  complications  and  careful  restoration  of  serum sodium concentration. Management depends on the cause, severity and time course. Based  on duration of development, hyponatremia can be (i) acute or (ii) chronic 

Table 1.4: Pharmacological Treatment for Hyponatremia 

ACUTE HYPONATREMIA

CHRONIC HYPONATREMIA

usually symptomatic and onset less than 48 hours Symptoms: neurologic deficit, seizures, coma and confusion

usually symptomatic and onset <48 hours 

Requires immediate treatment 

Give: C:  3%  sodium  chloride  (IV)  at  rate  of  1-2mEq/L/hr 

Alternative: 

C: sodium bicarbonate (IV) 8.4% 50ml over 5min 

Do NOT raise serum Sodium by >6mmol/L in 6hrs  

Stop infusion when symptoms have  
resolved 

Manage seizures and coma as appropriate 

No specific treatment if mild and asymptomatic 

If moderate to severe:  

Give:  A: 0.9% sodium chloride (IV) 

Do NOT raise serum Sodium by over 12mmol/L in the first 24 hours 

Stop correction when Sodium reaches 130mEq/L 

Once symptoms have resolved

Assess volume status using point of care Ultrasound (POCUS) for IVC as well as vitals assessment and quantify as either (i) Hypovolemic hyponatremia, (ii) Euvolemic hyponatremia and (iii) Hypervolemic hyponatremia

(i) HYPOVOLEMIC

(ii) EUVOLEMIC

(iii) HYPERVOLEMIC

Possible causes:

  • Dehydration (vomiting, diarrhea, sweating, third spacing, hydration with hyperosmolar fluids) 

Possible causes:

  • Psychogenic polydipsia
  • Iatrogenic
  • Syndrome of inappropriate ADH secretion)

Possible causes:

  • Renal Failure
  • Cirrhosis
  • Nephrotic syndrome
  • Congestive Cardiac Failure
  • MDMA (Ecstasy use)
  • Hypothyroidism
  • Psudohyponatremia
  • Give compound sodium lactate or 0.9% sodium chloride (IV) 250-500mls or 0.5-1ml/kg/hour (guided by BP response)
  • Prevent further exacerbation of hyponatremia
  • Prevent rapid overcorrection
  • Insert Foleys catheter to monitor output
  • Nil per oral, restrict fluids
  • Furosemide  (IV)  40mg  daily until fluid volume is corrected.

Note

  • Look for complications of over-correction such as Osmotic demyelination syndrome (ODS)
  • Hyponatremia can also lead to cerebral edema which may lead to increased Intracranial pressure (ICP)
  • Exercise associated hyponatremia is common in athletes and the cause is over hydration and not excessive water loss
  • Psychogenic polydipsia caused by over ingestion of large quantity of water in psychiatric patients or those on SSRI’s.

Severe  Hyponatremia:  (seizures,  coma,  signs  of  brainstem  herniation),  consider  treatment  for  cerebral edema and elevated ICP; give: 

  • 3% Sodium Chloride 3-5mls/kg over 15 to 60minutes to increase sodium by 2-4mmol/l
  • Close monitoring of Serum sodium initially hourly with target correction rate of no more than 8-10mmol/l/day and less than 0.5mmol/l/hour over 1-2hours

Hypovolemic Hyponatremia: 

  • Determine Sodium deficit: Total body Sodium deficit = (Desired sodium – actual plasma Sodium) x Total body water{0.6 x weight (kg) Men OR 0.5 x weight (kg) women}
  • Replace with 0.9% sodium chloride (IV)
  • Correct at no more than 0.5mmol/l/ hour

Disposition 

Symptomatic Hyponatremia, Severe hyponatremiamust be admitted to the HDU/ ICUfor continuous  biochemical and clinical monitoring.  If not available refer the patient to a higher health facility with  HDU/ ICU capabilities.