Electrolytes

Question 1

Hypocalcemia of immobilization

Answer 1

Immobilization can cause bone demineralization, especially in the setting of a bone injury which also prevents walking (spine, hip, femur, etc)

Correct with bisphosphonates

Question 2

SIADH in shock

Answer 2

May be physiologic (ADH secretion to try and preserve volume) or pathophysiologic (infarction of SIADH-secreting neurons causing release of pre-formed ADH)

The former is typically more likely, unless there is some specific evidence of other intracranial pathology.

Question 3

Electrolyte abnormalities in Cushing syndrome

Answer 3

• Remember, in Cushings there is extra glucocorticoid. This can overwhelm the enzymes guarding the mineralocorticoid receptor in the kidneys and produce excess mineralocorticoid signaling as well:
  
  • Hypokalemia (T wave flattening on ECG)
  • Hypernatremia

Question 4

When do you perform the full Ca gluconate/insulin + glucose/saline furosemide flush vs just saline furosemide flush for a patient with hyperkalemia?

Answer 4

• Any changes on ECG or symptoms or K above 6.5: Full house
• No ECG changes, no symptoms, K below 6.5: Saline furosemide flush alone is sufficient. Potassium binding resins can also be considered. In patients with impaired renal function, hemodialysis is preferred.

Question 5

Crystalloid vs colloid

Answer 5

Crystalloid: LR or NS. Give in most cases where capillary leakage is not a problem.

Colloid: Plasma or albumin. Give when capillary leakage is an issue (ARDS, for example)