0071643192.pdf

ENDOCRINE, METABOLIC, FLUID, AND

ELECTROLYTE DISORDERS

■ Sodium deficit can be approximated with this equation:

Na+deficit (in total mEq) =0.6×wt(kg)×(140−serum Na+)

■ Nonemergent treatment of hyponatremia involves treating the various un-

derlying causes of hyponatremia.

■ Pseudohyponatremia secondary to

■ Multiple myeloma or hyperlipidemia does not require treatment

■ Mannitol or contrast agents requires saline

■ Hyperglycemia requires insulin and saline

■ Hypervolemic hypo-osmolar hyponatremia secondary to

■ Renal failure requires dialysis

■ CHF, cirrhosis, or nephritic syndrome requires fluid restriction and

treating the underlying disorder

■ Euvolemic hypo-osmolar hyponatremia requires free water restric-

tion, saline, and possibly furosemide, depending on severity

■ Hypovolemic hypo-osmolar hyponatremia requires aggressive hydra-

tion with saline

COMPLICATIONS

■ Rapid correction of hyponatremia has been associated with neurologic de-

terioration known as central pontine myelinosis or osmotic demyelinating

syndrome (ODS).

■ ODS presents with flaccid paralysis, dysarthria, dysphagia, and hypotension.

■ Alcoholics, malnourished or chronically ill patients, women, and children

are at increased risk.

■ ODS has been associated with rates of correction >0.6 mEq/L/hr or > 25

mEq/48 hours in patients with hyponatremia >2 days. It has also been

associated with correction rates >2.5 mEq/hr with patients with hypona-

tremia between 1 and 2 days. No such risk has been seen in patients with

acute (<24 hours) hyponatremia.

Hypernatremia (Na+>145 mEq/L)

Hypernatremia results from either a hypovolemic state or iatrogenic Na+gain.

SYMPTOMS ANDEXAM

■ Headache, seizures, altered mental status

■ Vomiting, sweating, and hyperpnea may be symptoms of the underlying

disease causing the hypernatremia.

■ Poor skin turgor, tachycardia, low urine output

CAUSES

■ Three major types:

■ Dehydration

■ Inadequate water intake from physical or neurologic disability

■ Common in elderly and disabled patients

■ Osmotic diuresis secondary to hyperglycemia, DKA, or hyperosmo-

lar nonketotic coma

■ Iatrogenic: Drugs such as lithium or fluoride

■ Salt wasting: Diabetes insipidus whether central or nephrogenic

TREATMENT

■ Rehydration for hypovolemic patients initially with 0.9 NS as well as cor-

rection of the underlying mechanism

■ Furosemide and D5W for hypervolemic patients

Reserve use of hypertonic

saline for emergent cases of

hyponatremia such as

seizures or decreased mental

status, typically in patients

with Na <115 mEq/L.