Name
HYPONATREMIA
DESCRIPTION
DETAIL
CAUSES 1. Hypovolemic hyponatremia (extrarenal loss of sodium) . Gastrointestinal loss - vomiting, diarrhea . Third spacing - peritonitis, pancreatitis, burns, rhabdomyolysis . Skin loss - burns, sweating, cystic fibrosis . Lung loss - bronchorrhea 2. Hypovolemic hyponatremia (renal loss of sodium) . Salt losing nephritis . Mineralocorticoid deficiency . Diuretic . Bicarbonaturia - renal tubular acidosis, metabolic alkalosis . Ketonuria or anion gap acidosis . Partial urinary tract obstruction . Osmotic diuresis 3. Euvolemic hyponatremia . Hypothyroidism . Pure glucocorticoid deficiency . Drugs . Stress . Syndrome of inappropriate antidiuretic hormone release (SIADH). Causes include pulmonary and central nervous system disorders. 4. Hypervolemic hyponatremia . Nephrotic syndrome . Cirrhosis . Congestive heart failure . Renal failure 5. Redistributive hyponatremia . Hyperglycemia . Mannitol infusion . Pseudohyponatremia . Hypertriglyceridemia . Multiple myelomaLABORATORY . Serum sodium less than 135 mEq/L (135 mmol/L) . Plasma osmolality . Urine sodium . BUN . Creatinine . Hypovolemic hyponatremia . Plasma osmolality low . BUN/creatinine ratio greater than 20/1 . Urine sodium > 20 mEq/L (> 20 mmol/L) - renal loss . Urine sodium < 10 mEq/L (< 10 mmol/L) - extrarenal loss . Serum potassium > 5.0 mEq/L (> 5 mmol/L) - consider mineralocorticoid defi ciency . Euvolemic hyponatremia . Plasma osmolality low . BUN/creatinine ratio less than 20/1 . Urine sodium > 20 mEq/L (> 20 mmol/L) . Hypervolemic hyponatremia . Plasma osmolality low . Urine sodium < 10 mEq/L (< 10 mmol/L) in nephrotic syndrome, CHF, cirrhosis . Urine sodium > 20 mEq/L (> 20 mmol/L) in acute and chronic renal failure . Redistributive hyponatremia . Plasma osmolality normal or high . Glucose or mannitol levels elevated . Pseudohyponatremia . Plasma osmolality normal . Triglyceride or protein levels elevated
TYPENOTES
RISK FACTORS Excessive fluid intakeAPPROPRIATE HEALTH CARE β’ Inpatient treatment mandatory if acute hyponatremia or symptomatic β’ Inpatient treatment advised if asymptomatic and serum sodium less than 125 mEq/dL GENERAL MEASURES β’ Assess all medications patient is taking β’ Institute seizure precautions DRUG(S) OF CHOICE β’ Severe symptomatic hyponatremia: The use of hypertonic saline (3%) is clearly indicated only in patients who are both severely symptomatic and have sodium concentrations less than 120 mEq/L (120 mmol/L). Three percent saline should be used at a rate of 1 cc/kg/hr. This will raise the serum sodium level by approximately 1 mEq/L/hr (1 mmol/L/hr). The hypertonic saline infusion should only continue until a serum sodium of 120 mEq/L (120 mmol/L) is reached or the patient becomes asymptomatic. Avoid correction by more than 12 mEq/L/day (12 mmol/day). β’ Chronic hyponatremia: If hyponatremia does not improve with fl uid restriction or other appropriate treatment, consider using demeclocycline. In doses of 600-1200 milligrams per day, the drug produces a nephrogenic diabetes insipidus. β’ Maintenance: Clinical judgment Precautions: β’ Demeclocycline - photosensitivity and nausea can occur β’ Three percent saline-rapid correction of severe symptomatic hyponatremia has been associated with central pontine myelinolysis (CPM). This neurologic disorder induces loss of myelin and supportive structures in the pons and occasionally in other areas of the brain. CPM is seen one to several days after rapid correction of serum sodium and is characterized by gradual neurologic deterioration. PATIENT MONITORING β’ Serum sodium level should be monitored when clinically indicated. If three percent saline is used the sodium level should be checked hourly. β’ Volume status should be monitored if 3% or 0.9% saline is used PREVENTION/AVOIDANCE Dependent on underlying condition POSSIBLE COMPLICATIONS β’ Occult tumor may present with SIADH β’ Hypervolemia if saline used β’ Central pontine myelinolysis EXPECTED COURSE/PROGNOSIS With recognition and proper treatment a return to normal serum sodium and resolution of neurologic symptoms is expected. Prognosis is dependent on underlying condition.
RELATED DISEASE
Not Available Disease
DISEASE
INVESTIGATION
BLOOD SUGAR ( FASTING ), SERUM PROTEIN TOTAL, SERUM SODIUM, SERUM POTASSIUM, BLOOD SUGAR ( AFTER MEALS ), BUN