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10 Key Points Hyponatremia

1: What is Hyponatremia?
Serum sodium level below 135 mmol/L
Represents excess water relative to sodium in body
Often involves elevated antidiuretic hormone (ADH)

2: Hyponatremia Severity
Mild: 125-134 mmol/L
Moderate: 120-124 mmol/L
Severe: below120 mmol/L

3: Types of Hyponatremia
Hypoosmolar: Most common (hypovolemic, euvolemic, hypervolemic)
Iso-osmolar: "Pseudohyponatremia" due to elevated lipids/proteins
Hypertonic: Caused by osmotically active particles like glucose

4: Causes of Hypovolemic Hyponatremia
Results from loss of both water and sodium from ECF
Renal causes: diuretic use, salt-wasting nephropathy
Extra-renal causes: vomiting, diarrhea, sweating

5: Causes of Euvolemic Hyponatremia
Main cause: Syndrome of Inappropriate ADH Secretion (SIADH)
Other causes: psychogenic polydipsia, hypotonic IV fluids
Also seen in adrenal insufficiency and hypothyroidism

6: Causes of Hypervolemic Hyponatremia
Occurs when increase in total body water exceeds sodium
Results in edema or ascites
Common in heart failure, cirrhosis, and nephrotic syndrome

7: Recognizing Symptoms
Mild cases often asymptomatic
Symptoms appear below 125 mmol/L: nausea, headache, confusion
Severe cases: seizures and coma possible

8: Diagnosing Hyponatremia
Requires history, physical exam, and lab tests
Blood tests: sodium, osmolality, glucose, urea, creatinine
Urine sodium and osmolality help determine cause

9: Managing Hyponatremia
Treatment based on cause, severity, and symptoms
Options: fluid restriction, diuretics, isotonic saline
Severe cases may need hypertonic saline

10: Risks of Rapid Correction
Avoid rapid correction to prevent osmotic demyelination syndrome
Aim for 4-6 mmol/L increase in first 24 hours for severe cases
Maximum correction: 0.5 mmol/L/hr unless critically symptomatic