Hyponatremia

Rationale

Decreased serum sodium concentration is common with a multitude of underlying etiologies. Both hyponatremia and treatment of hyponatremia may be associated with neurological complications.

Causal Conditions

(list not exhaustive)

1. Hyponatremia with normal serum osmolality (e.g., hyperlipidemia)
2. Hyponatremia with high serum osmolality (e.g., hyperglycemia)
3. Hyponatremia with low serum osmolality
   1. Total body water low, elevated antidiuretic hormone (ADH) level (e.g., gastrointestinal loss, diuretic use)
   2. Total body water volume normal (e.g., syndrome of inappropriate ADH secretion, hypothyroidism, adrenal insufficiency)
   3. Total body water high, elevated ADH level (e.g., congestive heart failure, nephrotic syndrome, cirrhosis)

Key Objectives

Given a patient with hyponatremia, the candidate will diagnose the cause, severity, and complications, and will initiate an appropriate management plan, recognizing that severe hyponatremia can be life-threatening.

Enabling Objectives

Given a patient with hyponatremia, the candidate will

1. list and interpret critical clinical findings, including
   1. appropriate history and physical examination, with particular attention to assessment of volume status;
2. list and interpret key investigations directed towards establishing the underlying etiology, including plasma and urine osmolality and urine electrolytes;
3. construct an effective initial management plan, including
   1. a therapeutic approach based on the underlying etiology;
   2. understanding the risk factors for, and how to avoid central pontine myelinolysis;
   3. correcting serum sodium at an appropriate rate and understanding the risks and indications for more rapid correction of sodium concentration.