Electrolytes Flashcards
What are the electrolytes
Na K Cl CO2 calcium (order Mg and phosphorus separately)
What influences sodium retention
thirst
ADH
hyponatremia
( ADH is made in hypothalamus, goes to anterior pituitary, and then released to blood)
What influences NaCl retention
RAAS (increases Na/decreases K in blood)
ANP/catecholamines
renal factors (GFR)
What are the MC electrolyte abnormality in hospitalized patients
Hyponatremia (danger <125, seizures <120)
the faster Na drops, the more severe the situation
Hyponatremia is MC in
very young
very old
associated with pulmonary disease or CNS disorder
What are clinical manifestations of hyponatremia
HA, dizziness N/V lethargy weakness confusion HYPOventilation seizure, coma (Sx depend of level of cerebral edema)
What are some types of hyponatremia
- Pseudohyponatremia, redistributive hyponatremia
- Hypo, hyper, or euvolemic hyponatremia
What is pseudohyponatremia
falsley low sodium (<135) with normal osmolality
Sx: HLD, hyperproteinemia
(if suspected, talk to lab and get true Na level)
What is redistributive hyponatremia
in HYPERosmolar state, solutes in the ECF draw water from cells and dilute serum Na
ex: with high glucose, water follows so you get more water in the blood
(for every 100mg glucose >100mg, add 1.5 to Na)
What is hypovolemic hyponatremia due to
Renal (diuretics, addisons) non renal (burns, external or internal GI)
How do you treat hypovolemic hyponatremia
replace lost fluid (isotonic .9% NS) and treat underlying cause
What is hypervolemic hyponatremia due to
Cirrhosis
CHF
Renal failure
How do you treat hypervolemic hyponatremia
Diuretics
Dialysis
fluid restriction
What is Euvolemic hyponatremia due to
SIADH
Hypothyroid
adrenal insufficiency
How do you treat Euvolemic hyponatremia
Fluid restrict
treat underlying cause
What is SIADH
too much ADH is released= water retention, but SAME sodium excretion
leads to concentrated urine w/ low osmolality and euvolemia
What can cause SIADH
CNS disease small cell lung cancer meds surgery stress psych d/o
How do you treat SIADH
fluid restrict
If refractory: give hypertonic NS, demeclocycline, or lithium (vaptans are new)
How do you evaluate hyponatremia
good H&P (meds, underlying d/o, fluid status)
check labs (UA sodium/osmolality, CMP)
TSH, Sr cortisol
What do you do with hyponatremia
<125 or symptomatic: hospitalize
chronic: slow cautious correction (can use demeclocycline)
severe: hypertonic solution (3% NS)
What is the rate of correction for hyponatremia
Severe: 6-12 mEq in first 24 hr// <18 mEq in 48 hr
Chronic: <8 mEq in first 24 hr (check Na q2 hr)
What is central pontine myelinolysis
irreversible demyelination in and around the pons, but Sx dont occur until 1-3 days after the overcorrection of Na
Sx: dysarthria, dysphagia, AMS, hypotension, quadriparesis
What is hypernatremia
too little water relative to salt (Na >145)
either due to too little water intake, or too high sodium intake, or excess water loss
What happens to the brain in hypernatremia
high Na in the ECF causes the brain to shrink
What are some causes of hypernatremia
GI, skin, and renal losses ** diabetes insipidus hypothalamic lesion (decreased thirst) hypertonic Na solution drugs (diuretics, lithium)
What are clinical features of hypernatremia
Usually asymptomatic
thirst, AMS, weakness, seizure, coma, focal neuro deficit
Symptoms related to rate of onset (slow onset= less sx)
What does hypernatremia work up NEED
Urine osmolality! If urine osmolality is:
600): DI, external water loss
(if osm high and Na <25, vomiting/diarrhea)
(if osm high and Na >100, salt/hypertonic saline ingestion)
What is the normal homeostatic response to hypernatremia
create thirst and increase fluid intake
maximize urine concentration to prevent further water loss
What is diabetes insipidus
urine H2O loss with high sodium= dilute urine (oppo of SIADH)
water is not reabsorbed, collecting ductules are impermeable
What are types of diabetes insipidus
Central: 2/2 decreased ADH secretion in brain
Nephro: 2/2 kidneys not responding to ADH when present
Nephrogenic diabetes insipidus is
genetic of acquired (chronic renal insufficiency, lithium, amyloidosis)
How do you treat Nephrogenic diabetes insipidus
Thiazide (prevent NaCl reabsorption in DCT)
Amiloride (K sparing)
Chlorpropamide
NSAID (indomethacin)
What do you do with hypernatremia
Severe: hospitalize
replace H2O deficit (drink, NG, hypotonic IVF)
acute hypernatremia can be corrected more rapidly than chronic hypernatremia
How do you calculate H2O deficit
normal TBW (kg x 0.6) - current TBW (normal srNa x normal TBW)/(measured srNa)
Where is K mainly found
intracellularly (2% ECF)
it is excreted renally
it is regulated in the distal nephron
What does aldosterone do
increase Na reabsorption
increase potassium excretion
What are symptoms of hypokalemia
weakness, fatigue, muscle cramps, decreased DTR, ascending flaccid paralysis, cardia arrhythmia, hypercanis
What are hypokalemic EKG findings
prominent U waves
Flat T waves
PVC
ST depression
What is the way to remember Hypokalemia
YOUCRAMP hYpOkalemia U waves flat Cramp Respiratory failure/Rhabdo Anorexia, n/v Muscle weakness Paralysis, flaccid
What causes hypokalemia
Transcellular shift: insulin, caffeine, hyperthyroid, metabolic acidosis (more K goes into cell)
Renal loss*: high aldosterone, Cushing’s, renal tubular acidosis
Extrarenal loss: vomit, diarrhea, low Mag
(need mag to be normal to correct K)
What do you do with hypokalemia
Oral K* (IV if cant eat or emergent- give w/ lidocaine) -DONT push K >20 mEq/hr Telemonitor (arrhythmia) for every 0.1mEq <4 mEq, give 10 mEq K+ Severe: draw mag levels Hypokalemia can cause digoxin toxicity
What is hyperkalemia
When K >5 (severe >6.5)
rare in the absence of renal failure
What are symptoms of hyperkalemia
Asymptomatic usually
Ascending flaccid paralysis, arrhythmia
What is a way to remember hyperkalemia
AFACT! Arrhythmia Flaccid paralysis Ascending muscle weakness Conduction abnormality T waves peaked
Pseudohyperkalemia can be due to
Hemolysis
repeat fist clenching with tourniquet in place
Causes of hyperkalemia include
Impaired renal excretion (renal failure, Addisons, hypoaldosterone) Drugs (ACE, ARB, NSAID, Bactrim, K sparing diuretic) high intake (bananas, oranges) Rhabdo, low insulin, acidosis (K shift from ICF-ECF) (pH drop 0.1= K increase 0.5-1)
What is urgent hyperkalemia treatment
IV calcium (decrease threshold of myocyte)
NaHCO3 IV push (increase pH)
Insulin (shift K ECF to ICF)
Nebulized albuterol, IV lasix, dialysis
What is less urgent treatment for hyperkalemia
Kayexalate (exchange Na for K in gut= massive diarrhea full of potassium)
Lasix
treat underlying cause
What is “total calcium”
Free (ionized) + protein bound
calcium is inverse to phosphate
What does calcium help with
evaluating metabolism
monitoring hyperparathyroid, malignancy, renal failure
Where is calcium found
99% in bone
0.8-1% ICF
0.1-0.2% ECF
(in ECF, 50% free, 40% protein bound, 10% complexed)
What are the types of calcium
Ionized: not affected by albumin- cardiac function and clotting
Complexed: bound to citrate, sulfate, phosphate
Protein bound: if albumin decreases, so does calcium
What is calcium physiology
absorbed through GI (with vitamin D), stored in bone, excreted by kidney
low serum Ca triggers PTH release= bone resorption (release) an kidney reuptake (saves Ca)
high serum Ca triggers calcitonin release= inhibit bone resorption (stays in bone)
1g decrease in albumin= 0.8mg decrease in calcium
What is hypercalcemia
calcium >10.1 (common, self limiting)
Hypercalcemia symptoms are
“Stones, bones, abdominal moans, and psych groans”
renal stones, bone pain, abd pain, n/v, constipation, fatigue, memory loss, psychosis, depression
-loss of tone, HTN, SHORT QT
What causes hypercalcemia
Malignancy, primary hyperparathyroid**
thiazide, lithium, antacids, accutane
What do we evaluate in hypercalcemia
If >13, malignancy PTH is decreased in malignancy TSH cortisol plasma electrophoresis
How do you treat hypercalcemia
Volume expansion (NS)*
Calcitonin (takes 2 hr)
Pamidronate (decrease Ca in 1-2 d, stop bone resorption)
Zoledronic Acid (1st line for malignancy)
Prednisone
Dialysis (last resort)
How does hypocalcemia present
Tetany (increased NM excitability) paresthesias increased DTR chvostek, Trousseau prolonged QT, arrhythmia, hypotension
What tetany is seen with hypocalcemia
carpopedal tetany, lip toe finger paresthesia
Chvostek: tap facial nerve= face muscle contraction
Trousseau: occlude brachial artery for 3 min- carpal spasm
What causes hypocalcemia
low albumin large transfusion (citrate binds Ca) low Mag (inhibits PTH) low PTH renal failure low vitamin D intestine malabsorption
What is phosphate used for
investigating parathyroid and calcium abnormalities (phosphate is inverse of calcium)
DDx for hyperphosphatemia
renal failure
hypocalcemia
rhabdo
DDx for hypophosphatemia
chronic alcoholism diarrhea insulin refeeding syndrome decreased intestinal absorption
What is magnesium involved in
NM and cardiac function- binds to ATP and is excreted by kidneys (tied to Ca and K)
inhibits PTH= hypocalcemia
low mag= kidneys cant save K
DDx for hypermagnesemia
large amt. ingested
IV (preeclampsia Tx)
renal insufficiency
DDx for hypomagnesemia
malnutrition diarrhea alcoholism hypocalcemia cellular shift