Quiz 10: Disorders of Sodium Homeostasis

hypovolemic hyponatremia

What kind of hyponatremia is most associated with decreased effective arterial volume?

hypovolemic hyponatremia

occurs when the body loses both sodium and water but MORE sodium is lost than water

-heart failure

-cirrhosis

-GI loss

What conditions does hypovolemic hyponatremia occur in?

-RAAS activation (Ang II, Aldosterone)

-ADH

-Sympathetic nervous system

What are the chemical signals associated with decreased sodium reabsorption?

RAAS activation

increase NA reabsorption in kidney

ADH

increase water reabsorption leading to a dilution in sodium

sympathetic nervous system

increase proximal tubule NA reabsorption

135-145 mEq/L

What is the normal serum sodium range?

high glucose in the blood acts as an osmotic agent pulling water out of the cell into the bloodstream (hyponatremia even though total body sodium is unchanged)

How does hyperglycemia lead to hypertonic hyponatremia?

Characteristics of hypernatremia caused by diabetes insipidus

-loss of free water, not sodium

-high serum sodium + high plasma osmolality

-lrg volumes of very dilute urine

-can be central DI or nephrogenic DI

central DI

lack of ADH

nephrogenic DI

kidneys don't respond to ADH

pseudohyponatremia

sodium appears low on labs but serum osmolality is normal

very high lipids or proteins which displace plasma water and make sodium conc. measurement artificially low

What causes pseudohyponatremia?

symptoms of hyponatremia

due to brain cell swelling

-N, HA

-Confusion, dizziness

-lethargy

-seizures or coma

hypervolemic hyponatremia

-increase total body Na

-increases total body water

-hyponatremia + edema

hypovolemic hyponatremia

What type of hyponatremia is most often caused by diuretics?

thiazide diuretics

cause hypovolemic hyponatremia by decreasing sodium reabsorption leading to sodium loss exceeding water loss (hyponatremia)

hypovolemic hypernatremia

syndrome where a patient has high serum sodium but low total body sodium

water loss > sodium loss

-V/D

-burns

-excess sweating

-osmotic diuresis

What causes hypovolemic hypernatremia?

pseudohyponatremia

occurs when lipids or protein levels are markedly elevated and indirect potentiometry is used

direct ion selective electrodes

(such as blood gas analyzers) are not affected by psuedohyponatremia

serum osmolality

What remains normal in pseudohyponatremia?

measured vs calculated osmolality

What shows a gap in pseudohyponatremia?

hyperglycemia

is the most frequent cause of hypertonic hyponatremia

8-12

U.S. guidelines recommend correcting sodium no more than __________ to __________ mEq/L in the first 24 hours.

10; 18

European guidelines recommend ≤__________ mEq/L in 24 hours and ≤__________ mEq/L in 48 hours.

Diabetes insipidus

results from either inadequate secretion of AVP (central DI) or renal resistance (nephrogenic DI)

Desmopressin

is an AVP analog used to treat diabetes insipidus

-SSRIs

-Carbamazepine

-Cyclophosphamide

-Vincristine

-MDMA

-NSAIDs

-Antipsychotics

What are the common drugs causing SIADH?

Demeclocyline

induces nephrogenic diabetes insipidus to reduce renal response to AVP

Tolvaptan

a vasopressin antagonist used to increase aquaresis in SIADH

Thiazides

cause hyponatremia by blocking sodium reabsorption in the distal convoluted tubule while preserving the kidney's ability to concentrate urine

-HF

-cirrhosis

-nephrotic syndrome

What is hypervolemic hyponatremia often caused by?

275-290 mOsm/kg

What is the normal serum osmolality range?

effective molecules

sodium and glucose

BUN

is not an effective osmole because it crosses cell membranes freely

2.3 g/day

The USDA CDRR sodium intake target for adults and children ≥13 years is _________

1.8 g/day

For children ages 9-13 years, the target of sodium is ______

1.2 g/day

For children ages 4-8 years, the target of sodium is ________

-HTN

-CV events

-progression of CKD

What is excess sodium intake associated with the increased risk of?

RAAS

promotes sodium reabsorption via aldosterone

natriuretic peptides

promote sodium retention

common etiologies of hypernatremia

-osmotic diuresis

-GI water loss

-DM

-excess sodium admin

-burns

intracellular dehydration and brain shrinkage

Hypernatremia causes _______________, which may lead to confusion, seizures, and risk of intracranial hemorrhage.

10-12

Correction of hypernatremia should not exceed __________ to __________ mEq/L per day to avoid cerebral edema.

Tolvaptan and Conivaptan

vasopressin receptor antagonists that block V2 receptors to promote aquaresis

hypertonic saline

is reserved for severe symptomatic hyponatremia, such as cases presenting with seizures or coma

2-4

When using hypertonic saline, serum sodium should be monitored every __________ to __________ hours

chronic, asymptomatic euvolemic or hypervolemic hyponatremia cases

In what cases is fluid restriction considered the first line therapy?

1-1.5 L/day

What is the fluid restriction usually limited to less than each day?