FLUIDS AND ELECTROLYTES Flashcards
Symptoms of hypernatremia are usually not evident until Na+ reaches..
160 mEq/L
Causes of hypernatremia
Insensible losses (fever, hyperventilation, and burns), polyuria associated with excessive renal free water losses (osmotic diuresis, high output renal failure causing inability to concentrate urine) or hypotonic fluid losses due to perspiration or severe diarrhea
If perfusion is adequate, which types of fluids should be used to correct hypernatremia
0.5NS or D5W
Plasma Na should not be corrected at a rate faster than
0.5 to 1.0 mEq/L
Formula to correct Na
Water deficit=TBW x {(Plasma Na) / desired plasma Na) -1
Total intracellular K
40-50 mmol/kg body weight
How much potassium in ECF
2%
Content of K+ in gastric secretion
10 mEq/L
T wave flattening, U waves, prolonged QT, manifests at a plasma K below ..
3 mmol/L
Hyperkalemia in the surgical patient is usually due to..
Impaired renal excretion of K caused by oliguric renal dysfunction
How much of total body calcium within ECF is free
40%
Why do you get hypocalcemia with hyperventilation
Acid-base alterations affect calcium binding to albumin. alkalosis increases binding affinity of Ca to albumin, resulting in lower serum ionized calcium levels
Most frequent cause of hypocalcemia
Low serum albumin
Alternate causes of hypocalcemia
Acute pancreatitis, massive soft tissue infection, small bowel fistula, hypoparathyroidism
Massive blood transfusion effect n calcium
Induces hypocalcemia caused by chelation of calcium with citrate (each unit of blood contains approx 3 g of citrate). Liver metabolizes 3g citrate q 5 min.
Once patient is rehydrated, may enhance further calcium excretion by administering..
Furosemide
Why is hypophosphatemia common after liver resections
Regenerating hepatocytes use a lot of phosphate
Serum [uric acid] depends on
purine nucleotide pool size. GI tract is responsible for SECRETION, not resorption.
Urine Na below 10-15 suggests..
>20?
10-15: hypovolemia
>20: ATN
How to calculate FeNa
(USNa x Pcr/PNa x Ucr) x 100
If FeNa <1%, suggestive of..
> 99% of filtered Na has been resorbed. Likely hypovolemic state which enhances reabsorption of Na – > stimulated renin release from JG cells in afferent arterioles which results in production of angiotensin II
Hyper metabolic response seen 5 days after burn injury is associated with increased blood levels of
Cortisol. Up to 4 weeks after injury. Inhibits GH release.
How does hyperaldosteronism cause hypokalemia
Increased aldosterone leads to sodium retention – both potassium and H+ are excreted in urine in exchange for sodium.
Most common causes of hypoxia resulting in respiratory alkalosis
Pulmonary disease, exposure to high altitudes
Total body K
50 mEq/kg of body weight or approx 3500 mEq in total body stores
A serum K of 3.0 mEq/L usually represents a total body deficit of ..
100 to 200. Each additional 1.0 mEq/L decrease reflects an additional deficit of 200-400 mEq.
Primary cause of hypermagnesemia
Renal failure. Because of the ability of the kidneys to excrete large amounts of magnesium, hyperMg rarely occurs if renal function is normal.
Meds that can cause hypomagnesemia.
long term use of loop diuretics, cyclosporine, or ahminoglycosides
Primary causes of decreased urinary K excretion
hypovolemia, hypoaldosteronism, renal failure, and drugs like spironolactone or NSAIDs
Purines are broken down into
Ammonia and uric acid. Uric acid is notably poorly soluble in water and may form uric acid crystals.
How many kcal in 1 gram Nitrogen
150
How many grams protein per gram nitrogen
6.25
Amino acids utilized for energy yield approx how many kcal per gram
4
Dextrose provides approx how many kcal/g
3.4
