Chapter 17: Fluids and Electrolytes Flashcards
Total body water accounts approximately _ of total body weight
60%
The ECF is composed of ___ and ___, or interstitial, fluid
Intravascular and Extravascular
What are the 3 fundamental homeostatic equilibriums?
- osmotic equilibrium
- electric equilibrium
- acid-base equilibrium
The key point is that sodium is much more concentrated in the ECF (approximately ___ mEq/L) than in the ICF (approximately ___ mEq/L)
40
10
Why Na is equal in both compartment of ECF?
Because the capillary membrane is permeable to water and electrolytes
Why Na is increase in extracellular compared to intracellular?
Because the cell membrane is only permeable to water but not to electrolytes
Measure of solute concentration per unit mass of solvent
Osmolality
Measure of solute concentration per unit volume of solvent
Osmolarity
When two solutions are separated by a membrane that is permeable only to water, water crosses into the compartment with ___
the more concentrated solution to equalize the ion concentration in each.
Contribute the most to osmotic pressure in ECF
Na, HCO3 and Cl plus glucose
Formula to calculate effective osmolality or Tonicity
2 x Na + glucose / 18
What will happen if you add 1L of water to the ECF?
it will cross the cell membrane into ICF to equalized ECF osmolality. TBW will expand and decrease in osmolality
What will happen if you add 1L of isotonic saline to the ECF?
no movement of water into cells and will only produce ECF expansion
What will happen if you give hypertonic plasma and hypotonic plasma?
Hypertonic plasma will shrink the cell
Hypotonic plasma will swell the cell
Two types of dehydration
water loss (hyper-osmolality) salt loss (hypo-osmolality)
Example of salt loss type of dehydration
vomiting sweating diarrhea bleeding CKD
Hyponatremia is defined as a serum Na
<138
symptoms of hyponatremia occurs if serum Na
=/<15
How many percent of heart failure patient has hyponatremia?
approximately 20%
How many percent has mild hyponatremia in hospitalized patient?
15-30%
If patient has hyponatremia what is the next step?
volume status and calculate plasma osmolalities
Hyperosmolar hyponatremia >295
Isoosmolar hyponatremia 275 - 295
Hypoosmolar hyponatremia >295
Pathophysiology of hyperosmolary hyponatremia
large amount of osmotically active solutes accumulate in the ECF space. example is Hyperglycemia
Each 100mg/dL increase of glucose it will ___
decrease plasma Na by 1.6mEq/L
administration of mannitol, glycerol and maltose will cause ___
osmolar gap and hyponatremia
Difference between measured osmolality and calculated osmolality
osmolar gap (NV around 10)
Example of isoosmolar hyponatremia
severe hyperproteinemia or hyperlipidemia
Two important hyponatremic disorders are the
SIADH and less common cerebral salt-wasting syndrome
Difference of SIADH to cerebral salt-wasting syndrome
SIADH may also cased by non cerebral disease and volume status is normal
Intoxication of this substance is uncommon but important cause of hyponatremia that may be profound
Methylenedioxymethamphetamine (MDMA or Ecstasy)
The most important symptoms of hyponatremia are due to its effects on the
brain
Moderately severe symptoms often start when a plasma [Na+] is ___
<130 mEq/L
Severe symptoms often start when a plasma [Na+] is ___
<120 mEq/L
Initially if hypoosmolar the brain will ___. After 48 hours the brain will adapt and will release
swell producing intracranial hypertension.
Na, K, Cl, glycine and taurine
Symptoms is hypoosmolar hyponatremia is sever and persistent in what population?
SIADH
Children
Menstruating women
Hypoxia
Diagnostic criteria of SIADH
Hypotonic hyponatremia (<275) Increase urinary osmolality (>200) Elevated urinary Na (>20) Clinically euvolemia Normal other organs
Experts recommend that when duration is unknown, the hyponatremia should be assumed to be chronic and treated as ___ with a longer correction time.
chronic
Acute vs chronic hyponatremia
24-48 hours
If no urinary osmolality, you can compute by
for a specific gravity (π) of 1.005, UOSM = 05 × 35 = 175 mOsm/L.
As a rule, only in patients with edematous syndromes and in patients with vomiting and diarrhea will UNa+ be found to be
<10 mEq/L
The most important guides for therapy in hyponatremia is
symptoms (hyponatremic encephalopathy)
When the patient presents with severe neurologic symptoms (vomiting, seizures, reduced consciousness, cardiorespiratory arrest), the initial treatment
infusion of 3% hypertonic saline as recommended by European guidelines
Raising serum sodium by ___ is typically all that is required to see an improvement in severe neurologic symptoms.
5 mEq/L
T or F: When symp- toms are mild or moderate (nausea, confusion, headache) or in chronic hyponatremia, the [Na+] correction should be faster than for acute hyponatremia
False. it should be slower
For chronic hyponatremia [Na+], the correction rate should not exceed ___ in high-risk patients and ___ h in low-risk patients
6 mEq/24 hour
12 mEq/24 hour
Hypertonic (3%) saline can be in hyponatremia given at a low infusion rate
0.5 to 1 mL/kg/h
In addition in treatment of hyponatremia using saline we can also add what?
Furosemide 20mg IV
Osmotic demyelination syndrome is caused by rapid correction of hyponatremia
> 12 mEq/L/24 h
Treatment for overcorrection of
Na
5% dextrose in water at 3ml/kg/h
loop diuretics
desmopressin
Hypernatremia is defined as serum or plasma ___
[Na+] >145 mEq/L and hyperosmolality (serum osmolality >295 mOsm/L).
Population at risk of hypernatremia
Elderly patients, decompensated diabetics, infants, and hospitalized patients
If severe hypernatremia develops in the course of minutes to hours, such as from a massive salt overdose in a suicide attempt, a suddenly shrinking brain may prompt ___
intracranial hemorrhage
Based on volume status, hypernatremia can be classified into 3
- hypovolemic hypernatremia (decreased TBW and total body Na+ with a relatively greater decrease in TBW)
- hypervolemic hypernatremia (increased total body Na+ with normal or increased TBW)
- normovolemic hypernatre- mia (near normal total body sodium and decreased TBW)
FDA recommends against vasopressin antagonists in patients with ___
liver cirrhosis
Therapy for cerebral salt wasting
isotonic (-.9%) nacl and Fludrocortisone – nacl orally at home
Therapy for SIADH
Water restriction.
Enhanced Na+ and protein intake + furosemide. Vasopressin antagonists* can be used for [Na+] <125 mEq/L. Demeclocycline. Lithium.
Polyuria
> 3000ml of urine/24hours
Drug may case nephrogenic diabetes insipidus
Demeclocycline
Drug may cause interstitial nephritis
NSAIDs
Example of normovolemic hypernatremia
Central DI (urine osm <300) Partial DI (urine osm 300-800) Nephrogenic DI (urine osm <200)
Patient has Urine osm of more than 800 and urine Na less than 10. What is your consideration?
extrarenal hypovolemia hypernatremia
Severe hypernatremia ___ yields a mortality of ___
Severe hypernatremia (i.e., a [Na+] >150 to 160 mEq/L) yields a mortality of 75%
A BUN/creatinine ratio ___ is indicative of hyperosmolar dehydration.
A BUN/creatinine ratio >40 is indicative of hyperosmolar dehydration.
Steps in treatment of hypernatremia
- isotonic 0.9% saline
- treat underlying cause
- compute for free water deficit
When the adaptation of brain cells is incomplete (onset over
<48 hours), the correction rate of acute hypernatremia can be performed at a rate of ___
1 mEq/L/h
If hypernatremia is chronic (onset over >48 hours), the rate of correction should be slower to avoid the risk of cerebral edema, at no more than ___
If hypernatremia is chronic (onset over >48 hours), the rate of correction should be slower to avoid the risk of cerebral edema, at no more than 0.5 mEq/L/h or 10 to 12 mEq/24 h.
A disease where the ability of the kidney to reabsorb free water is compromised.
Diabetes insipidus characterized as
- polyuria
- polydipsia
- increased volume of hypoosmolar urine
2 types of diabetes insipidus
- central (also called neurogenic), due to inadequate ADH secretion
- renal (also called nephrogenic), when ADH secretion is normal or increased but the v2R receptors of the kidney’s collecting duct cells do not respond appro- priately to ADH.
The most common clinical symptoms and signs are ___
The most common clinical symptoms and signs are excessive thirst, polydipsia, and polyuria
Diabetes insipidus a spot check in the ED without water deprivation will typically reveal a UOSM of
<300 mOsm/L
Central diabetes insipidus is treated with
the synthetic hormone desmopressin, as a nasal spray, 10 micrograms (0.1 mL) every 12 hours, or PO, 0.05 milligrams every 12 hours, as starting doses.
Nephrogenic diabetes insipidus is treated with
low-salt, low-protein diet, adequate hydration, and the careful use of one to three agents that act together to concentrate urine in these patients: a thiazide diuretic, the potassium- sparing diuretic amiloride, and indomethacin.
Hypokalemia is defined as a serum [K+] of
<3.5 mEq/L.
Most frequent cause of hypokalemia
- insufficient dietary intake
- intracellular shift
- increase losses
Hypokalemia makes the resting potential more electronegative which produces in ECG
- enhancing depolarization; the reduction in [K+] conduction delays repolarization, causing prolonged QTc, flattened T waves, and the appearance of U waves in the ECG
Symptoms of hypokalemia with start at serum ___
2.5 mEq/L
Arrythmias to watch out in hypokalemia
atrial fibrillation
torsades de pointes
ventricular tachycardia
ventricular fibrillation
Cause of hypokalemia that mimics thiazide diuretic use
gitelman;s syndrome
Cause of hypokalemia that mimics loop diuretic use
bartter’s syndrome
UNa+ value <30 mEq/L and a UOSM value less than POSM suggest
polyuria
How to compute transtubular K gradient?
(Urinary K+ × POSM)/(UOSM × Plasma K+) with normal result of 8-9 mEq/L
transtubular K gradient result of <5 mEq/L suggest ___ and value of <3 mEq/L suggest ___
values <5 mEq/L suggest hyperaldosteronism; if paralysis is present, values <3 mEq/L suggest hypokalemic periodic paralysis.
A calcium/phosphate ratio ___ on a spot urine is 100% sensitive and 96% specific for thyrotoxic hypokalemic periodic paralysis.
A calcium/phosphate ratio >1.7 on a spot urine is 100% sensitive and 96% specific for thyrotoxic hypokalemic periodic paralysis.
Level of mild, moderate and severe hypokalemia
mild = >3 mEq/L moderate = 2.5 - 3 mEq/L severe = <2.5 mEq/L
In tintinally, fluid correction of hypokalemia is ___
500 mL of a saline solution is 40 mEq, to be infused in 4 to 6 hours in a peripheral line
In most cases, hypokalemic patients are also hypomagnesemic.
Thus, magnesium (20 to 60 mEq/24 h) may be added to the infusion both to optimize tubular reuptake of potassium and to contrast proar- rhythmic effect of hypokalemia.
Hyperkalemia is defined as measured serum [K+] of ___
> 5.5 mEq/L
The most common cause is factitious hyperkalemia due to
release of intracellular potassium caused by hemolysis during phlebotomy.
What is the role of Calcium in hyperkalemia?
calcium antagonizes the effects of hyperkalemia at the level of the cell membrane, raising the threshold potential
Death from hyperkalemia is usually the result of ___
diastolic arrest or ventricular fibrillation
In hyperkalemia, elevated spot urine K (>20mEq/L) suggest ___
extra renal cause
In hyperkalemia, low urine K+ output (<10 mEq/L) suggests ___
oliguric kidney failure or drug effect, such as angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers.
Treatment modalities for hyperkalemia
- membrane stabilization
- intracellular shift of K
- removal/excretion of K
This study does not recommend the routine administration of sodium bicarbonate for hyperkalemia unless there is concomitant metabolic acidosis.
Cochrane review of 2015
Causes of hyperkalemia
- pseudohyperkalemia
- intracellular shift to extracellualr
- potassium load
- decrease potassium excretion
This oral was previously used to excrete potassium but noted with intestinal necrosis
sodium polystyrene sulfonate
2 oral K binding agents can be use in ED
patiromer
sodium zirconium cyclosilicate
___ enhances the toxic cardiac effects of digitalis.
hypercalcemia enhances the toxic cardiac effects of digitalis.
The total body content of magnesium (Mg2+) is ___
24 grams, or 2000 mEq,
____ of which is fixed in bone and only slowly exchange- able.
50% to 70%
Most of the remaining Mg2+ is found in the ICF space, with a concentration of approximately ___
40 mEq/L
Circulating Mg2+ is ___ to ___ bound to proteins (mainly albumin), ___ to ___ complexed, and ___ to ___ ionized,
Circulating Mg2+ is 25% to 35% bound to proteins (mainly albumin), 10% to 15% complexed, and 50% to 60% ionized
How many percent of circulating Mg2+ is active form?
50% - 60% inonized
The normal dietary intake of Mg2+ is approximately ___ and is found in vegetables such as dry beans and leafy greens, meat, and cereals.
The normal dietary intake of Mg2+ is approximately 240 to 336 milligrams/d and is found in vegetables such as dry beans and leafy greens, meat, and cereals.
Hyperkalemia 12LECG changes levels
Prolonged PR interval, tall peaked T waves, short QT interval
Flattening of the P wave, QRS widening
QRS complex degradation into a sinusoidal pattern
6.5–7.5 = Prolonged PR interval, tall peaked T waves, short QT interval
7.5–8.0 = Flattening of the P wave, QRS widening
10–12 = QRS complex degradation into a sinusoidal pattern
Membrane stabilization used for hyperkalemia
calcium chloride (5-10ml IV) 1-3 ml calcium glutinate (10-20ml IV) 1-3 ml
T or F: Renal reabsorption of Mg2+ is carried out with sodium and water and is unidi- rectional
True
___ enhances neuromuscular activity (thus provoking tremors and cramps) by
rapidly decreasing ionized [Mg2+] and [Ca2+] at the same time.
respiratory alkalosis
Drug that causes hypomagnesemia
proton pump inhibitor
diuretic therapy
Hypomagnesemia is common in acute illness; it has been found in ___ of hospitalized patients and in up to ___ of medical intensive care patients.
Hypomagnesemia is common in acute illness; it has been found in 12% of hospitalized patients and in up to 65% of medical intensive care patients.
Hypo- calcemia does not develop until [Mg2+] falls below ___
Hypo- calcemia does not develop until [Mg2+] falls below 1.2 milligrams/dL
Treatment principles for hypomagnesemia
- treat or stop cause of hypomagnesemia
- asymptomatic patient may use supplementation
- for severe and symptomatic hypomagnesemia, urgent IV replacement is mandatory
- chronic Mg2+ def may require >50 meds of oral Mg (6 grams of MgSO4 per day)
- spironolactone - reducing incidence of arrhythmias in congestive heart failure
In life-threatening conditions hypomagnesemia (torsades de pointes, eclampsia) treatment is
1 to 4 grams or 8 to 32 mEq diluted in at least 100 mL of 5% dextrose or normal saline (0.9%) solution can be administered in 10 to 60 minutes under continuous monitoring
Hypermagnesemia is more commonly seen in the ___
Hypermagnesemia is more commonly seen in the perinatal setting secondary to the treatment of preeclampsia or eclampsia
The possibility of hypermagnesemia should be considered in patients with ___
hyperkalemia or hypercalcemia
Severe symptomatic hypermagnesemia can be treated with ___
Severe symptomatic hypermag- nesemia can be treated with 10 mL of 10% calcium chloride IV over 2 to 3 minutes
Signs and symptoms of hypermagnesemia and magnesium level
- 0–3.0 = Nausea
- 0–4.0 = Somnolence
- 0–8.0 = Loss of deep tendon reflexes
- 0–12.0 = Respiratory depression
- 0–15.0 = Hypotension, heart block, cardiac arrest
___ is the most abundant mineral in the body.
Calcium (Ca2+)
Total body Ca is?
15grams/kg of body weight or about 1kg in an average-sized adult
Ca2+ is ___ bound in bone as phosphate and carbonate
99%
The normal daily intake of Ca2+ is ___ milligrams
The normal daily intake of Ca2+ is 800 to 3000 milligrams
Excretion of Ca2+ is primarily via the ___
stool
Plasma [Ca2+] is between
Plasma [Ca2+] is between 8.5 and 10.5 milligrams/dL (4.3 to 5.3 mEq/L or 2.2 to 2.7 mmol/L)
1 mEq/L = 2 milligrams/dL = 0.5 mmol/L
3 forms of calcium
50% ionized which is active
40% protein bound which is inactive
10 % bound to anions which are phosphate, carbonate and citrate
Total serum Ca is equal to?
Ionized [Ca2+] plus the product of 0.8 and total protein.
T or F: Alkalosis produces a decrease in ionized fraction with no change in the total serum [Ca2+]
True
T or F: Each 0.1 rise in pH lowers ionized [Ca2+] by about 3% to 8%.
True
When Ca is increase our body will release ___ and if Ca is decrease our body will release __
Calcitonin = resorption PTH = demineralization
Ca2+-sensing receptor58,59 is mainly present on plasma membranes of ___
parathyroids
kidney
bones
thyroid
Physiology that increases urinary secretion of Ca
- hypercalcemia
- metabolic acidosis
- hypervolemia
- loop diuretics
Cause of hypocalcemia that decrease production of 25(OH)D3?
liver failure
Cause of hypocalcemia that decrease synthesis of 1,25(OH2)D3
renal failure and hyperphospathemia
Hypocalcemia is defined by an ionized [Ca2+] level ___
<2.0 mEq/L (<4 milligrams/dL or <1.1 mmol/L).
Example drugs that causes hypocalcemia
- Phosphates (e.g., enemas, laxatives)
- Phenytoin, phenobarbital
- Gentamicin, tobramycin, dactinomycin, foscarnet
- Cisplatin
- Citrate
- Loop diuretics
- Glucocorticoids
- Magnesium sulfate
- Bisphosphonates, calcitonin, denosumab
- Cinacalcet
If serum Ca falls the neuronal membranes becomes ___
permeable to sodium which enhancing excitation and cause contraction
The most characteristic ECG finding in hypocalcemia is a ___
prolonged QTc interval
Serum level of Ca that can produce T wave mimics ischemia
<6.0mg/dL
T or F: Chvostek and Trousseau signs only seen in hypocalcemia?
False. can also seen in hypomagnesemia and respiratory alkalosis
1 mEq of elemental Ca2+ is equal to ___
20 milligrams of elemental Ca2
Regimen of correction of hypocalcemia
Regimens can be 500 to 3000 milligrams of elemental Ca2+ by mouth daily, in one dose or up to three divided doses. The dose must be individualized for each patient, according to the cause and severity of hypocalcemia
IV Ca2+ is only recommended is cases of?
symptomatic or severe hypocalcemia (ionized [Ca2+] <1.9 mEq/L or <0.95 mmol/L)
T or F: IV Ca2+ gluconate is preferred over IV calcium chloride (CaCl2) in nonemergency settings due to the dangers of extravasation with CaCl2 (calcinosis cutis)
True
T or F: With severe acute hypocalcemia, 10 mL of 10% CaCl2 (or 10 to 30 mL of 10% Ca2+ gluconate) may be given IV over 10 to 20 minutes and repeated every 60 minutes until symptoms resolve or followed by a continuous IV infusion of 10% CaCl2 at 0.02 to 0.08 mL/kg/h (1.4 to 5.6 mL/h in a 70-kg patient)
True
T or F: IV Ca2+ should be used with caution in patients taking digitalis because hypocalcemia can potentiate digitalis toxicity.
False. hypercalcemia
When to give Calcium chloride in massive transfusion?
During massive transfusions, if the blood is being given faster than 1 unit every 5 minutes, 10 mL of 10% CaCl2 can be given after every 4 to 6 units
Hypercalcemia is defined as
A total [Ca2+] >10.5 milligrams/dL or an ionized [Ca2+] level >2.7 mEq/L
What is the level of Calcium in mild, moderate and severe hypercalcemia?
mild hypercalcemia = 10.5 to 11.9 milligrams/dL
moderate = 12 to 13.9 milligrams/dL
severe = >14 milligrams/dL
What is the most frequent renal effect of hypercalcemia?
loss of concentrating ability
A mnemonic sometimes used for the signs and symp- toms of hypercalcemia
stones (renal calculi)
bones (osteolysis)
moans (psychiatric disorders) groans (peptic ulcer disease, pancreatitis, and constipation).
On ECG, hypercalcemia may be associated with ___
- depressed ST segments
- widened T waves
- shortened ST segments
- QT intervals.
Levels of [Ca2+] above ___ may cause cardiac arrest.
20 milligrams/dL
corrected Ca2+ (milligrams/dL) equation?
corrected Ca2+ (milligrams/dL) = measured total Ca2+ (milli- grams/dL) + 0.8 (4.0 – serum albumin [grams/dL])
corrected Ca2+ (mmol/L) = measured total Ca2+ (mmol/L) + 0.02 (40 – serum albumin [grams/L])
Treatment for hypercalcemia
if patient is symptomatic or >14mg/dL even without symptoms administer 0.9% normal saline at 500 to 1000ml/hr for 2 - 4 hours.
furosemide of 20 -40mg
corticosteroids (prednisone 1to 2 mg/kg PO or hydrocortisone 200 to 300mg tiv)
It decreases mobilization of Ca from bone through reduction of osteoclastic activity
Corticosteroids
Hypercalcemia associated malignancy can give
IV bisphosphonates are now considered first-line therapy
T or F: Zoledronic acid is recommended; for a corrected [Ca2+] level of 12 milligrams/dL or higher, 4 milligrams as a single dose can be given IV over 15 minutes. Calcitonin works more rapidly than bisphos- phonates and can be given at a dose of 4 units/kg SC or IM.
True
Phosphorus mainly exist as?
hydroxyapatite (85%)
How many percent of phosphorus is found at ECF?
1%
Serum phosphorus in newborns and adults?
Serum [PO43–] decreases with age from a range of 4.0 to 7.0 milligrams/dL in newborns to 2.5 to 5.0 milligrams/dL in adults.
What is the total phosphorus store in a man?
700 grams (10 - 15grams/kg)
Gut absorption of phosphorus is localized in 2 different sites which are?
1st part of duodenum and jejunum and ileum
Increase absorption of phosphorus in proximal tubule is?
- hypoparathyroidism
- volume depletion
- hypocalcemia
- presence of growth hormone.
Hypophosphatemia is defined as serum [PO 3–]?
Hypophosphatemia is defined as serum [PO 3–] <2.5 milligrams/dL
Severe symptoms of phosphorus may occur at what level?
<1mg/dL
What drug may cause pseudohypophosphatemia?
mannitol
The symptoms of hypophophatemia is due to?
depletion of adenosine triphosphate and reduction of erythrocyte 2,3-diphosphoglycerate
In asymptomatic or mildly symptomatic patients, hypophosphatemia may be treated orally with?
ith skim milk ([PO43–] 1 gram/L) or oral prepa- rations such as Neutra-Phos®, one to two tabs PO four times daily, or K-Phos®, one tab PO four times daily, which contain 150 to 250 mil- ligrams per tablet (PO43–: 1 mmol/L = 3.1 milligrams/dL)
Hyperphosphatemia is defined as serum [PO43–]?
Hyperphosphatemia is defined as serum [PO43–] >4.5 milligrams/dL
Causes of hypophophatemia
- shift of phosphate into cells
- increased renal excretion
- decreased GI absorption
Cause of hyperphophatemia
- decrease in renal excretion of PO43–
- addition or movement of PO43– from ICF to ECF
- drugs
In clinical practice, the most important cause of hyperphosphatemia is ___
acute or chronic renal failure
Ir reduced survival and function of platelets and red and white blood cells and impaired macrophage function
hypophosphatemia
Phosphate correction
<1 mEq/L = 0.6 with duration of 6–72
1–1.7 mEq/L = 0.3–0.4 with duration of 6–72
1.8–2.2 mEq/L = 0.15–0.2 with duration of 6–72
