Fluids, Electrolytes, Renal Flashcards
Total body and water and extracellular fluid ______ with increasing gestational age
Decrease
At what age does intracellular fluid begin to make up a larger part of total body water
Around three months of age
What percent of body weight is total body water at 24 weeks and at term
90% at 24 weeks gestation and 80% at term delivery
How to correct freewater deficit
Administer four mL/kilo of free water for everyone mEq per liter increase in sodium over 145
When is ADH present in the fetus?
11 weeks gestation
Calculation of plasma osmolality
(2 x plasma sodium) + (glucose mg/dL/18) + (BUN/2.8)
Genetics of congenital nephrogenic diabetes insipidus
X-linked recessive for the vasopressin receptor defect, and autosomal for the Aquaporin defect
Management of nephrogenic diabetes insipidus
Hydrate, monitor electrolytes, thiazides to increase urine concentrating ability (potassium supplementation as needed.)
Correction of sodium for high glucose
Sodium is decreased by 1.6 mEq/L for each 100 increase in glucose (pseduohyponatremia)
So to calculate= Measured Na + (glucose -100) x 0.016
Calculation of sodium deficit
[Na desired- Na current] x 0.6 x weight (kg)
Where does most of bicarbonate reabsorption occur?
60 to 80% occurs in the proximal tubule
Net acid excretion in the urine equals
(Titratable acids + ammonium) - non-reabsorbed bicarbonate
Where does acidification of the urine occur?
Cortical and medullary collecting tubule cells
Calculation of anion gap
Na - (chloride + bicarb)
Calculation of bicarb replacement
0.3 x bicarb deficit x weight
Problem in type I RTA
Can’t secrete H+ in distal tubule
Problem in type II RTA
Decreased or absent proximal tubule bicarb reabsoprtion
Dehydration, failure to thrive, normal blood pressure, nephrocalcinosis, polyuria, normal serum calcium
Barrter syndrome
Management of Bartter syndrome
Potassium supplementation, +/- thiazide diuretics, +/-indomethacin
When are first nephrons formed
8 weeks gestation
When does urine production start
10-12 weeks gestation
The preterm infant has recused ability to contrite urine due to:
- Tubule insensitivity to vasopressin
- Short loop of henle
- Low osmolality of medullary interstitium (secondary to limited Na reabsorption in thick ascending loop)
- Low serum urea
Calculation of fractional excretion of sodium
(Urine sodium x plasma creatinine) / (urine creatinine x plasma sodium) x100
<1% normal; 1-2.5% pre-renal; >3% intrinsic renal failure
Where is potassium reabsorbed/secreted?
Reabsorbed proximal tubule and ascending loop of Henle
Secreted in distal tubule and collecting ducts
Where is sodium reabsorbed in kidney
2/3 in proximal tubule
20% in ascending loop of Henle
10% in distal tubule/collecting duct
Where is reabsorption of Calcium in kidney
Proximal tubule and loop of Henle by passive movement, limited by sodium
Distal tubule and collecting ducts (active)
Calculation of tubular reabsorption of phosphorus
1- [(urine phosphorus x plasma creatinine) / (urine creatinine x plasma phosphorus)]
Where is phosphorus reabsorbed
80% in proximal tubule, 10% in distal tubule, remaining excreted
Genetics and pathogenesis of pseudohypoaldosteronism
X-linked recessive
Unresponsiveness of renal tubule to aldosterone
Lab findings in pseudohypoaldosteronism
Low sodium, high potassium, metabolic acidosis, increased aldosterone, increased renin
Estimated GFR formula
(0.45 x height)/ plasma creatinine
Creatinine clearance calculation
(Urine creatinine x volume) / plasma creatinine
Where is most protein reabsorbed in kidney
Proximal tubule
What is the injury if you see leukocytouria in the urine?
UTI, obstructive uropathy, or glomerulonephritis
What is the injury if you see red blood cell casts in the urine?
Glomerular injury
What is the injury if you see white blood cell casts in the urine?
Infection, renal interstitial/tubular injury
What is the injury if you see epithelial/granular casts in the urine?
Dehydration or renal interstitial/tubular injury
What is the injury if you see hyaline casts in the urine?
Severe proteinuria, dehydration
Proteinuria, hypoproteinemia, hyperlipidemia, and edema
Congenital nephrotic syndrome
Genetics of Finnish congenital nephrotic syndrome
Autosomal recessive on chromosome 19, 19q13.1, gene NPHS1, gene product is called nephrin
Gene and chromosome in autosomal recessive PKD
Chromosome 6p21, PKHD1, which encodes fibrocystin/polyductin-expressed on cilia of renal cells and bile duct cells
Gene and chromosome in autosomal dominant PKD
Chromosome 16 (a few on 4p)
Fanconi syndrome
Proximal tubule dysfunction, leading to excess urinary losses of amino acids, glucose, phosphate, and bicarbonate
Management of Fanconi syndrome
Supplement with sodium phosphate, sodium and potassium citrate, and vitamin D
Genetics of Fanconi syndrome
Autosomal dominant but generally sporadic
What is cystinosis?
Defective carrier-mediated transport of cysteine leading to excess cysteine in lysosomes of many cells
Diagnosis and management of cystinosis
Diagnosed with cornea lamp exam demonstrating cystine crystals, and management is with cysteamine and renal transplant
Genetics and pathogenesis of lowe syndrome
X-linked recessive, gene defect leads to an enzyme deficiency disrupting, the Golgi apparatus
Cataracts, glaucoma, mental deficiency, muscular hypotonia, renal, tubular, dysfunction, proteinuria, cryptorchidism
Lowe syndrome
The recessive form of type I RTA can be associated with what?
Hearing loss
Calculation of free water deficit
4 mL x weight x (desired change in serum Na)
Modalities of continuous renal replacement therapy, that incorporate hemofiltration use the principle of what to remove solutes
Convection
Slow continuous ultra filtration is useful for what
To remove fluid in patients with volume overload, but it will not correct acidosis electrolyte, anomalies or uremia, because the low ultra filtration rate has minimal solvent drag they are for trivial amounts of solutes are removed from plasma
In cvvhd how are solutes removed
By diffusion across the concentration gradient
Is CVVHD or CVVH more likely to remove low molecular weight solutes
CVVHD
(But is less likely to remove high molecular weight solutes, and water)
Primary brain energy substrate during periods of hypoglycemia
Lactate
