Lytes Flashcards
How do you calculate percentage of total body water?
- males: BW x 0.6
- females: weight x 0.5
What percentage of total body water is intracellular, extracellular, and intravascular?
- ⅔ is intracellular
- ⅓ is extracellular (¼ of this is intravascular)
What is an individuals total blood volume?
- pediatric: 80cc/kg
- adult 70cc/kg
What maintenance fluid is preferred for neonates and why?
D5 ¼ NS + 20mEq K due to their decreased ability to concentrate urine
What are the contents of lactated ringers?
- 130 mEq Na
- 4 mEq K
- 2.7 mEq Ca
- 109 mEq Cl
- 28 mEq HCO3
What are the contents of normal saline?
154mEq Na and 154mEq Cl
How much sodium does an average person need a day? Potassium?
- sodium is 1-2 mEq/kg
- potassium is 0.5-1 mEq/kg
How is FENa calculated?
(UNa/SNa) / (UCr/SCr)
How is serum osmolality calculated?
- 2Na + glucose/18 + BUN/2.8
- simplies to 2Na + 10
How is sodium deficit calculated?
(140 - actual) x TBW
How is free water deficit calculated?
TBW x {(actual Na - 140)/140}
What do labs look like for diabetes inspidus?
- high serum osmolality
- low urine osmolality
- high serum Na
How can you distinguish central from peripheral DI?
give DDAVP, central patients will respond
How are neurogenic and nephrogenic diabetes insipidous managed?
- neurogenic: vasopressin, DDAVP
- nephrogenic: free water supplementation, thiazide diuretic
What EKG abnormality is seen with hypoCa?
prolonged QT interval
What are common symptoms associated with hypocalcemia?
- weakness
- paresthesia
- anxiety
- cramping
- seizures
- chovstek’s sign (perineal twitching with facial nerve tapping)
- trosseau’s sign (carpal-pedal spasm with BP cuff inflation)
- heart block, torsades
What is the most common cause of hypercalcemia?
- outpatient: hyperparathyroidism
- inpatient: malignancy
What are the symptoms and management of hypercalcemia?
- “stones, bones, groans, thrones, and psych overtones”
- renal stones, bone pain, abdominal pain, constipation, psychosis
- create with NS volume expansion, loop diuretics, bisphosphonates, calcitonin, glucocorticoids, and dialysis
Hypomagnesemia most commonly causes what EKG abnormality?
- prolonged QT is most common
- can progress to torsades
How is anion gap calculated? What’s normal?
- gap = Na + K - Cl - HCO3
- normal < 12
Vomiting leads to what electrolytes abnormalities?
hypokalemic, hypochloremic, metabolic alkalosis
What cation primarily determines serum osmolality?
sodium
What is the primary intracellular cation?
potassium
What are the three most common electrolyte abnormalities seen in those with re-feeding syndrome?
- hypophosphatemia
- hypokalemia
- hypomagnesemia
A baby with pyloric stenosis will present with what electrolyte abnormalities?
- hypochloremic
- hypokalemia
- metabolic alkalosis (paradoxical aciduria where Na reabsorption and K secretion leads to proton secretion in urine)
Acidosis does what to the oxygen dissociation curve?
shifts it to the right, allowing easier unloading of O2
Diarrhea causes what electrolyte abnormality?
hypokalemic metabolic acidosis (non-gap)
