Fluids & Electrolytes

Question 1

Electrolytes controlled via Na-K ATPase: ECF and ICF

Answer 1

ECF: Na+, Cl-, HCO3-
ICF: K+, Mg, Phosphates

Question 2

Fluid and Electrolyte Replacement Intravenous solutions (IV):

Answer 2

Saline equivalents: crystalloids
Normal Saline or Lactated Ringers (Isotonic solution)

Water equivalents:
D5W- sugar water
900 mOsm/L Max through peripheral line
3% Normal Saline (1028mOsm/L) centrally**

Question 3

Hyponatremia—etiologies

Answer 3

Hypovolemia:
GI losses
Renal losses—thiazide diuretics

Normovolemia:
SIADH
Primary polydipsia/marathon runners
Low dietary solute intake

Hypervolemia:
CHF
Cirrhosis

Question 4

Hyponatremia: Sodium Values

Answer 4

130 generally not directly treated

Question 5

Hypervolemic Hyponatremia Tx.

Answer 5

Examples are CHF, cirrhosis, renal failure
Restrict fluids: 1000-1200 ml/day
Restrict sodium: 1000-1200 mg/day
Utilize loop diuretics to remove excess fluid

Question 6

Therapy for Severe Hyponatremia

Answer 6

Tx—3% hypertonic saline:
Goal to increase Na+ by 4-6 meq/L in 24 hr. period
Measure serum Na+ every hour
Measure urine output

Risk if correct too rapidly:
Develop osmotic demyelination
High risk populations:
Women and children acute postop
Patients w/ hyperacute hyponatremia –psychosis, marathons, ecstasy
Those w/ intracranial pathology

Question 7

Hypernatremia:

Answer 7

Na+ >145 meq/L

Question 8

Hypercalcemia

Answer 8

Ca+ >10.5
Cancer and primary hyperparathyroidism*** primary causes
Drugs: thiazide diuretics, calcium supplements, lithium
Mild-moderate >13
SX: N/V, anorexia, constipation, Polyuria/-dypsia, Neuro/psych symptoms

Question 9

Hypocalcemia:

Answer 9

Ca+ <8.5 mg/dL
Etiologies: Hypoparathyroidism, Vitamin D deficiency, loop diuretics, phosphates
Correct level for hypoalbuminemia!
Hypomagnesemia associated with refractory severe hypocalcemia***
Symptoms:
tetany, paresthesias around mouth—hallmark symptoms