Hypernatremia

Rationale

Increased serum sodium concentration is encountered more frequently in older adults and in infants. Both hypernatremia and treatment of hypernatremia may be associated with neurologic complications.

Causal Conditions

(list not exhaustive)

1. Water depletion (dehydration)
   1. Decreased water intake (e.g., impaired thirst)
   2. Increased loss
      1. Renal loss (e.g., osmotic diuresis)
      2. Gastrointestinal loss (e.g., diarrhea)
      3. Increased insensible loss (e.g., prolonged exercise)
2. Sodium gain (e.g., hypertonic fluid replacement)
3. Salt poisoning (e.g., intentional or accidental addition of salt when preparing infant formula)

Key Objectives

Given a patient with hypernatremia, the candidate will diagnose the cause, severity, and complications, and initiate an appropriate management plan. In particular, the candidate will recognize that most cases occur in the frail older population due to conditions associated with water depletion.

Enabling Objectives

Given a patient with hypernatremia, the candidate will

1. list and interpret critical clinical findings, including those derived from
   1. a history aimed at identifying the common triggers and the clinical consequences of hypernatremia, and
   2. a physical examination that includes careful assessment of volume status and the neurologic effects of hypernatremia;
2. list and interpret critical investigations, including
   1. estimation of water deficit, and
   2. specific laboratory and other investigations for underlying medical conditions (e.g., blood glucose level, brain imaging);
3. construct an effective initial management plan, including
   1. establishing a short-term plan and a long-term plan for correcting the sodium concentration, with recognition of the neurologic consequences of overly rapid correction, and
   2. correcting causes of hypernatremia.