How To Correct Hyponatremia ?

How To Correct Hyponatremia ?

Serum sodium concentration and serum osmolarity normally are maintained under precise control by homeostatic mechanisms involving stimulation of thirst, secretion of antidiuretic hormone (ADH), and renal handling of filtered sodium. Irreparable harm can befall the patient when abnormal serum sodium levels are corrected too quickly or too slowly.

Classification

• Mild Hyponatremia - Na 135-130mEq/L,
• Moderate Hyponatremia - Na 129-125mEq/L,
• Severe Hyponatremia - Na 124-120mEq/L
  
• Life Threatening - Na <>

Prehospital Care

Prehospital treatment is directed toward treatment of symptoms (eg, seizures, arrhythmias) in severely symptomatic patients; the underlying hyponatremia is unlikely to be recognized prior to evaluation in the ED.

Emergency Department Care

Formulas for the dose and rate of hypertonic saline are based on a sodium deficit and have not been prospectively studied. These formulas should only be used as a guideline, requiring frequent retesting of serum sodium level.

Administration of 3% NaCl should only be required in patients with severely symptomatic hyponatremia (eg, seizures) or potentially in patients with Serum Sodium Level of less than 110 mEq/L

Total Sodium Deficit

Na Deficit (mEq) = (Desired Na – Measured Na) X 0.6 X (Weight in Kilograms)

Correction of Hyponatremia Using 3% Saline

Volume of 3% Saline (L) = (Na Deficit)/513 mEq Na/L

The rate of correction of Chronic Hyponatremia should not exceed 0.5 mEq/L per hour.
The rate of correction of Acute Hyponatremia should not exceed 1 - 2 mEq/L per hour.

Sodium levels should not be corrected to above 120-130 mEq/L or increase by more than 12 mEq/L per day. However, if necessary, as with a patient with Hyponatremia-Induced Seizure or Agitated Confusion, the initial rate of correction can be rapid, provided that the final rate of correction does not exceed 15 mEq/L per 24 hours.

Time Needed For Hyponatremia Correction

Time Needed for Correction = (Desired Na – Measured Na)/0.5 mEq/L per hour

The Rate of Infusion of Hypertonic Saline

Rate = (Volume of 3% Saline)/(Time Needed for Correction)

Other Solution That Can Be Used

Lactated Ringers : Contains 130 mEq/L = 0.130 mEq/ml
0.9% NaCl : Contains 154 mEq/L = 0.154 mEq/ml
1.8% NaCl : Contains 380 mEq/L = 0.380 mEq/ml
3% NaCl : Contains 513 mEq/L = 0.513 mEq/ml

Other Concern

1. Stop therapy when serum sodium concentration approaches 120-130 mEq/L, symptoms resolve, or serum sodium concentration has increased by 15 mEq/L in 24 hours or less.
2. Furosemide increases excretion of free water and can be used (1 mg/kg) in conjunction with isotonic or hypertonic saline.
3. Once normal renal function is ascertained, try to normalize potassium levels prior to or concurrently with the correction of hyponatremia.
4. Monitor serum and urine electrolyte levels. Initially, recheck them in 2 hours, then at least every 4 hours until the patient's levels are stabilized.
5. Aggressive treatment of hyponatremia should always be weighed against the risk of inducing Osmotic Central Pontine Myelinolysis (CMP) / Osmotic Demyelination Syndrome.
   
6. Although rare, osmotic myelinolysis is a serious complication and can develop one to several days after aggressive treatment of hyponatremia. Typical features are Disorders of Upper Motor Neurons including Spastic Quadriparesis and Pseudobulbar Palsy, and Mental Disorders ranging from Confusion to Coma. The risk is increased in persons with hepatic failure, potassium depletion, large burns, and malnutrition.

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