Lytes Flashcards
How is TBW calculated?
as Kg x 0.6 = Liters total body water
How much of total body water is intracellular?
2/3rds
How much of extracellular body water is intravascular?
25%
How is total body water distributed?
- 2/3rds intracellular
- 1/3rd extracellular
- 25% intravascular
- 75% interstitial
What is the blood volume of an average adult? average child?
- 70kg male has 5L blood volume
- children have 80cc/kg blood volume
What is the makeup of LR?
- 130 mEq sodium
- 4 mEq potassium
- 2.7 mEq calcium
- 109 mEq chloride
- 28 mEq bicarb
How much sodium and potassium does a person need each day?
- 0.5 - 1.0 mEq of potassium
- 1.0 - 2.0 mEq of sodium
How many calories are in a liter of D5?
- D5 = 50g of dextrose
- dextrose has 3.4kcal/g
- total = 170 kcal
How is serum osmolality calculated?
- Osm = 2 x Na + glucose/18 + BUN/2.8
- simplifies to 2 x Na + 10
How can you differentiate SIADH from excess free water?
- calculate serum osmolality (2 x Na + 10) and compare it to urine osmolality
- if urine osmolality is lower than likely excess free water
- if urine osmolality is higher than likely SIADH
How is SIADH treated?
- fluid restriction
- normal saline
- vaptans (vasopressin antagonists)
- demeclocycline
What are the two most likely causes of hypernatremia?
dehydration and diabetes insipidus
How is free water deficit calculated?
(actual Na - desired Na)/desired Na x kg x 0.6
What are the symptoms of hypocalcemia?
- weakness
- perioral tingling
- Chovstek’s sign (tap on facial nerve and get a perioral twitch)
- Trousseau’s sign (carpal pedal spasm with blood pressure cuff)
How is calcium corrected for albumin?
- normal albumin = 4
- add 0.8 to calcium for every 1 albumin is below 4
- e.g. if albumin is 2, add 1.6 to calcium
What are the two most common causes of hypercalcemia?
- in an outpatient: hyperparathryoidism
- in an inpatient: malignancy
What are the symptoms of hypercalcemia?
stones, bones, groans, and psychiatric overtones
How is hypercalcemia treated?
- crystalloid resuscitation
- loop diuretics
- biphosphonates
- calcitonin
- glucocorticoids
- dialysis
How much should PaCO2 affect pH?
- change in pH = 0.8 x change in CO2
- .1 change in pH for every 12 change in CO2
How is anion gap calculated?
Na + K - Cl - HCO3, normal is < 12
What are the possible explanations for a gap acidosis (> 12)?
- M: methanol
- U: uremia
- D: DKA
- P: paracetamol/paraldehyde
- I: isoniazid/iron
- L: lactate
- E: ethanol, ethylene glycol
- S: salicylates
What are the possible causes of a non-gap metabolic acidosis (< 12)?
- diarrhea
- RTA
- fistulas
- hyperchloremia
- acetazolamide
What is the primary intracellular cation?
potassium
What is the effect of lasix on potassium?
potassium wasting
