Corrected sodium level
When hyperglycemia is present, the underlying sodium concentration (corrected sodium concentration) can be estimated by adding 1.6-2.4 mEq/L (average of 2 mEq/L) to the reported sodium concentration for every 100 mg/dl increase in plasma glucose above 100 mg/dl.
E.g. In a patient with Na+ level, 145 and plasma glucose 300 mg/dl, corrected Na+ will be: 145 + 1.6 X 2 to 145 + 2.4 X 2 = 148.2 to 149.8 (average 149 mEq/L)
Hyponatremia correction rate
Correct acute hyponatremia (<48 hours duration): 1 to 2 mEq/L/hr
Correct chronic hyponatremia (>48 hours duration): 0.5 mEq/L/hr (risk of Osmotic demyelination Syndrome with over-rapid correction)
Rule of Six
- Six a day makes sense for Safety
- Six in six hours for severe symptoms and Stop
For all patients with hyponatremia, the goal is 6 mEq/L during the initial 24 hours. For those with severe symptoms (seizure, severe delirium, unresponsiveness), the goal is preloaded in the first 6 hours, postponing subsequent efforts to increase serum sodium level until the next day. While different sources will cite different ranges, targeting six is a conservative approach. If you overshoot by one or two mmol then you will still be well within the safe range.
Sodium content of Different fluids in 1 litre
- NS (0.9% NaCl) = 154
- 3% NaCl = 3/0.9 X 154 = 513
- 1/2 NS (0.45% NaCl) = 1/2 X 154 = 77
- RL = 130
- 5% Dextrose in water (D5W) = 0
Calculate Sodium Deficiency and Volume of Infusate
- Determine desired sodium level (often 120 mEq/L)
- Subtract current sodium level
- Adjust sodium deficiency for TBW/kg body weight by multiplying with 0.6 (0.6 for men and children, 0.5 for women and elderly men, 0.45 for elderly women)
- Multiply by patient’s weight in kg
E.g.
- 120 desired level – 114 current level
- 6 X 0.6 = 3.6 Meq/L/kg (adjusted)
- 3.6 meq/L/kg X 60 kg = 216 mEq/L (needed to replace sodium deficiency)
Volume of infusate: 216/513 = 0.42 L of 3% NS, i.e. 17.5 ml/hour
Severe Hyponatremia with CNS symptoms
If the patient is altered, comatose, seizing, or has neurologic findings, then raise the sodium by a little bit.
Give 3% saline, 100-150ml IV over 10-20 minutes (2 ml/kg)
May repeat for total of 3 doses with serum sodium repetition
Route: May be given peripherally through any reasonable IV
Aim: To raise Na+ by 4 to 6 mEq/L (Each 100 ml will raise sodium by ~2 mEq/L)
Rule of 100s
To prevent rapid over-correction and osmotic demyelination syndrome.
- Insert foley catheter and monitor input/output
- If urine output >100 ml/hour, send stat urine osmolarity and urine sodium
- If urine osmolarity <100, consider administering 1 mcg DDAVP IV
- Continue steps 2-3 as per urine output