Sodium and Water Disorders Flashcards
Normal adults are considered to have a minimal obligatory water intake of ________ mL/ day
1600 mL/day
what is the breakdown of water needs per day
Ingested water- 500mL
Water in food- 800mL
Water from oxidation – 300mL
what is the normal water loss per day
2.5-3 Liters per 24 hours
what is the breakdown of water losses
Loss from urine 500mL
Skin- 500mL
Respiratory Tract- 400mL
Stool- 200mL
what conditions require increased fluid needs
burns, diarrhea, dehydration, fever
what conditions require decreased fluid needs
CHF, renal failure, iatrogenic fluid overload, mechanical ventilation
where does most of the water go?
intracellular fluid
what is determined by the concentrations of effective osmoles in the ECF.
tonicity
_________ osmoles are solutes that can not move freely across cell membranes.
Effective
what is the main effective osmole in the ECF?
Sodium
when there is decreased wall stress in the atria and pulmonary vasculature the hypothalamus is stimulated to release what? This is the low pressure system
ADH
what stimulated the reinin-angiotensin-aldosterone system
Baroreceptors in aortic arch, carotid sinus, and juxtaglomerular apparatus
(high pressure system)
________ cleaves angiotensin to generate Angiotensin I
Renin
Angiotensin I is then cleaved by _______________ to Angiotensin II
angiotensin converting enzyme (ACE)
what does angiotensin II lead to
Stimulation of Aldosterone secretion by adrenal gland
Increased reabsorption of NaCl from proximal tubule
Central stimulation of thirst and secretion of ADH
Arteriolar vasoconstriction
What solutions are hypotonic
D5W
1/2 NS
what is an isotonic solution
Normal Saline
lactated ringers
what is a hypertonic solution
3% saline
is dextrose a good volume replacement
no, good for patients who need calories
where does dextrose distribute?
to all compartment
what types of saline are hypotonic? where are they distributed
1/4 NS and 1/2 NS
distributed to intracellular (mainly), plasma, interstitial
where is 0.9% NS (isotonic) distributed
ECF only
problem w/ 0.9% NS in large volumes
acidosis
when is 0.9% NS useful
dehydration/ hypovolemic state
Is 3% saline commonly used?
No, hypertonic and high solute in extracellular compartment draws water from intracellular compartment
More physiologic isotonic solution than NS
Confined to extracellular compartment
Lactated Ringers
Is NS or lactated ringers safer in large volumes
Lactated ringers
when is a fluid imbalance desirable?
correction for dehydration
fluid overload in CHF patients
what is the major determinant of ECF osmolality?
Sodium
what 2 other things contribute to ECF osmolality?
chloride
bicarbonate
what is the normal range for serum sodium
135-145 mEq/L
do serum sodium concentrations always reflect total body sodium concentrations
No
If a patient is hypernatremic what must you look at next?
volume status (Hypervolemia, isovolemic, hypovolemic)
If a patient is hyponatremic, what must you assess next?
Tonicity
can be hypertonic, isotonic, hypotonic (3 different fluid levels)
what antiepileptic can cause SiADH?
carbamazepine
what antiepileptic can cause diabetes insipidus?
phenytoin
a count of the number of particles in a fluid sample
osmolality
what regulates osmolality
ADH
ADH is also secreted in response to hypovolaemia and this stimulus will over-ride any response to _________________ .
serum osmolality
what is the normal range of urine osmolality
50-1200 mmol/kg
what is the best measure of urine concentration
urine osmolality
The main factor determining urine concentration is the amount of water which is resorbed in ______ and ________ in response to ADH.
the distal tubules and collecting ducts
In a dehydrated patient with normally functioning pituitary and kidneys, a small volume of highly _____________ urine will be produced.
concentrated
when is serum osmolality used?
investigation of hyponatraemia and identificaiton of an osmolar gap
when does hypernatremia usually occur?
hospitalized patients (elderly and breastfed infants more common)
what is the serum level of Na in hypernatremia?
Na > 145 mEq/L
always associated w/ hypertonicity- serum > 295 mOsm
IF a person is hypernatremic what do you classify them according to?
ECF status
what can lead to hypervolemic hypernatremia?
Sodium overload
sodium bicarb therapy
albumin therapy
mineralcorticoid excess
what can cause isovolemic hypernatremia?
diabetes insipidus
osmotic diuretic
hyperglycemia
no access to water
what can cause hypovolemic hypernatremia (losing both water and Na but losing water to greater extend than sodium)
renal disorders diuretics diarrhea laxative abuse excess sweating
what is a Disorder of antidiuretic hormone (ADH) release that causes isovolemic hypernatremia.
diabetes insipidus
what are the 2 types of diabetes insipidus
central
nephrogenic
what is the clinical presentation of diabetes insipidus?
dehydration
volume depletion
increase in urine output
causes of central DI?
CNS tumors
cerebral clots of bleed
head trauma
TB, syyphilis
what are nephrogenic causes of DI?
renal diseases
what drugs can induce DI?
lithium, phenytoin, foscarnet, demeclocycline
what can decrease in brain volume in DI cause?
Decrease in brain volume can cause rupture of cerebral vein, hemorrhages, and irreversible neurological damage
symptoms of DI?
lethargy, weakness, confusion, restlessness, irritability
what would a patient w/ hypervolemic hypernatremia look like?
edematous
pulmonary congestion
how do you treat hypervolemic hypernatremia?
need to dilute sodium and remove excess sodium and fluid
administer a hypotonic solution (D5W)
and add a loop diuretic (furosemide)
what can happen if serum Na is decreased too quickly
cerebral edema, seizures, permanent neurological damage
how do you treat isovolemic hypernatremia?
replace water deficit
give D5W at 1.3-2 mL/kg/hour
ADH (vasopressin) analgoue/ DDAVP
adjunct- HCTZ, carbamazepine, chlorpropamide
how do you treat nephrogenic diabetes insipidus
thiazide diuretic and dietary sodium restriction
what is the problem w/ hypovolemic hypernatremia
losing more fluid than Na, but losing both of them
Tx for hypovolemic hypernatremia
restore intravascular volume w/ NS
replace free water deficit
can switch to more hypotonic solution once fluid is replaced
what is hyponatremia
Serum sodium < 135 mEq/L
what is the most common electrolyte abnoramlity in hospitalized patients?
hyponatremia
do all patient w/ hyponatermia need Na?
No
what can cause high plasma osmolaity hyponatremia?
hyperglycemia
Mannitol
What can cause normal plasma osmolality hyponatremia?
hyperproteinemia
hyperlipidemia
bladder irrigation
what can cause low plasma osmolality hyponatremia
figure out if urine is dilute, it yes then primary polydipsia, recent osmostat
If urine isn’t dilute need to access fluid status
If a patient is hyponatremic w/ hypertonic what is usually the cause?
excess osmols in ECF (including serum)
usually caused by excess glucose
how do you treat hyponatremic w/ isotonic fluid
tx underlying cause of hyperproteinemia
hyperlipidemia
bladder irrigation
have excess water in relation to existing fluid stores.
hypotonic hyponatremia
have excess total body Na with excess of ECF
hypervolemic hypotonic hyponatremia
causes of hypervolemic hypotonic hyponatremia
CHF
cirrhosis
hypoalbuminemia
patient has normal total body Na, but there is a small increase in ECF.
isovolemic hyptonic hyponatermia
causes of isovolemic hyptonic hyponatermia
imbalance of ins and out SIADH excessive ADH activity (SSRI, Ecstasy) defective renal diluting mechanism altered thirst psychiatric disorder
Release of ADH when not needed or increased response to ADH
opposite of diabetes insipidus
SiADH
what are non-drug causes of SiADH?
CNS tumors, cerebral thrombosis or bleed, head trauma
meningitis, pneumonias, TB
What can cause drug induced SiADH
NSAIds, carbamazepine, vincristine
opioids, phenobarbital, thiazide diuretics
TCAs, ecstasy
what is due to a loss of sodium and ECF, but more Na
Hypovolemic Hypotonic Hyponatremia
causes of Hypovolemic Hypotonic Hyponatremia
GI losses (V/D)
renal lsoses (diuretic)
weating
iatrogenic
for Hypovolemic Hypotonic Hyponatremia if loss of sodium is from an extrarenal cause, the urine sodium concentration will be ____?
low (<20mEq/L)
for Hypovolemic Hypotonic Hyponatremia if loss of sodium is from an renal cause, the urine sodium concentration will be ____?
high (>20 mEq/L)
if Na is <120 mEq/L what can happen??
Seizures
coma
death
is serious and can develop one to several days after aggressive treatment of hyponatremia by any method, including water restriction alone. Shrinkage of the brain triggers demyelination of pontine and extrapontine neurons that can cause neurologic dysfunction, including quadriplegia, pseudobulbar palsy, seizures, coma, and even death.
osmotic demyelination
what increase the risk of the complication of osmotic demyelination?
Hepatic failure, potassium depletion, and malnutrition
what is Hypervolemic Hypotonic Hyponatremia Treatment
restrict salt and water
restrict fluids to 1 to 1.2 L/day
restrict dietary sotium to 1-2 grams per day
may need to administer loop diuretics to remove water
may consider hypertonic saline if rapid onset (<48 hours)
Hypovolemic Hypotonic Hyponatremia Treatment
replace sodium and volume loss w/ NS
don’t correctly too quickly (avoid demyelination)
if rapid onset can use 3% saline infusion
Tx for Severe Euvolemic Hypotonic Hyponatremia
Hypertonic saline
fluid restriction
loop diuretic
Isovolemic Hypotonic Hyponatremia Treatment
need to correct cause (hypothyroidism, glucocorticoid deficiency)
induce negative water bounce (want outs to exceed ins)
fluid restrict to 1 to 1.2 L/day
Isovolemic Hypotonic Hyponatremia – Treatment of SiADH
treat underlyign cause
restrict fluid intake
may need hypertonic saline
pharmacotherapy for SiADH
demeclocycline (abx) (inhibits ADH)
lithium (stops ADH at collecting tubules)
phenytoin (inhibit ADH release)
Severe Euvolemic Hypotonic Hyponatremia Treatment
Hypertonic saline
Fluid restriction
Loop diuretic
