FEN Flashcards
Correction of free water deficit
Administer 4mL/kg for every 1meq/L increase over 145
Administer 3mL/kg for Na >170
Plasma osmolality
(2 x Na) + (glucose / 18) + (BUN / 2.8)
Extrarenal ADH effect
Arterial vasoconstriction stimulating renal mesangial cell contraction, decrease renin secretion, and increase ACTH secretion
Obstructive renal disorder can cause what with ADH
Nephrogenic DI because of the pressure which decreases aquaporin expression
SIADH management
Free water restriction
If Na <120, replace with NaCl
Consider furosemide
Diabetes insipidus management
Central - vasopressin/desmopressin
Nephrogenic - thiazides to increase urine concentrating ability
Na content in hypergylcemic state
Na decreased by 1.6meq/L for each 100 increase in glucose (mg/dL)
Hyponatremia bucket differential
Decreased weight - renal loss or extrarenal loss
Increased or normal weight
Hyponatremic renal losses differential
Na losing nephropathy
Diuretics
Adrenal insufficiency
Hyponatremic extrarenal losses
GI losses
Skin losses
Third spacing
Cystic fibrosis
Increased weight hyponatremia
Nephrotic syndrome CHF SIADH Acute or chronic renal failure Excess water infusion Cirrhosis
Na deficit equation
deficit=(desired Na -current Na)x0.6xwt
The 0.6 is the percent body water which should be higher in preterm
Hypokalemia differential buckets
Decreased stores: with hypertension or with normal BP
Normal K stores
Decreased K stores hypokalemia and HTN
Renovascular disease, excess renin, excess mineralocorticoid, Cushing syndrome
Decreased K stores normal BP
Renal: RTA, fanconi syndrome, bartter syndrome, antibiotics, diuretics, ampho B
Extrarenal: skin loss, GI loss, high carb diet, enemas, malnutrition
NaHCO3 replacement equation
NaHCO3 replacement (mEq) = 0.3xHCO3 deficit xweight
RTA workup
Serum electrolytes
Urine pH and electrolytes (calcium, citrate, potassium, oxalate)
RBUS
Urine blood partial pressure of CO2 (nl >20; type I RTA <20)
Tubular reabsorption of phosphate (TRP)
Type I RTA
Distal Cannot secrete H Normal renal bicarbonate threshold Most primary causes are AD Can have secondary causes Urine pH >6.2
Type II RTA
Proximal
Decreased or absent proximal tubular HCO3 reabsorption, reduced renal bicarbonate reabsorption threshold
Large urine losses of bicarbonate
Can have urine pH <5.3
FENa calculation and percentages
FENa = (urine Na x plasma Cr) / (urine Cr x plasma Na)
<1% normal
1-2.5% prerenal
>3% intrinsic
But premature infants have difficulty holding on to Na so their FENa may be elevated even though they are intravascularly depleted. However also limited ability to excrete Na load secondary to lower GFR
Tubular reabsorption of phosphorus (TRP) equation
TRP = 1 - [100 x (urine Ph x plasma Cr) / (urine Cr x plasma Ph)]
Estimated GFR calculation
Estimated GFR = (0.45 x height (cm)) / (plasma cr (mg/dL))
Creatinine clearance calculation
Creatinine clearance = (urine Cr x volume) / plasma cr
Tubular dysfunction
Fanconi syndrome
Lowe syndrome (oculocerebrorenal syndrome)
Cystinosis
Adverse effects of NaBicarb administration for metabolic acidosis
Increased PCO2
Decreased ionized calcium (because bicarb causes calcium to bind albumin)
Decreased K
Increased Na
Hypertonic so increased risk of IVH
Renin secretion in response to
Decreased renal perfusion (hypotension, volume depletion), an increased sympathetic activity
Effects of angiotensin II
Stimulates release of aldosterone, which acts on the kidney and increases sodium reabsorption, increases chloride, increases, potassium, secretion, increases hydrogen, secretion
Angiotensin II also increases sodium and water resorption, arteriolar, vasoconstriction, stimulates release of ADH, stimulates release of aldosterone, activates vitamin D via PTH, activates erythropoietin
GFR calculation
0.45 x height (cm) / plasma creatinine (mg/dL)
Use 0.33 for preterm infants
Creatinine clearance
(Urine creatinine x volume (ml/min)) / plasma creatinine
Fanconi syndrome describe lab findings and management
Lab: decreased phosphate, decreased TRP, metabolic acidosis, hypokalemia, normal GFR
Management: supplement with sodium phosphate, sodium and potassium citrate, and Vit D
Cystinosis pathogenesis, describe lab findings and management
Patho: defective carrier mediated transport of cystine leading to excess cystine in lysosomes of many cells
Lab: normal plasma cystine levels
Diagnosis by cornea slit lamp - crystals
Management: cysteamine, renal transplant
Oculocerebrorenal syndrome patho, diagnosis, and management (lowes syndrome)
X linked
Enzyme deficiency disrupting the Golgi apparatus
Cataract, glaucoma, mental deficiency, hypotonia, tubular dysfunction
Increased amniotic fluid AFP
Management: symptom directed
Disorders that cause nephrocalcinosis
Williams syndrome
Type 1 RTA
Neonatal primary hyperparathyroidism
Bartters syndrome
