Nephrology Flashcards
Serum osmolality equation
2Na + BUN/2.8 + Glucose/18
Leading cause of metabolic acidosis in children
Diarrhea
Electrolyte derangement in pyloric stenosis
Hypochloremia
Hypokalemia
Hyponatremia
Metabolic alkalosis
Anion gap
Na - (Cl + HCO3)
Most common cause of NAGMA in children
Diarrhea
Causes of NAGMA
Ureterostomy
Small bowel fistula
Extra chloride
Diarrhea
Chronic diuretic use
Adrenal insufficiency
RTA
Pancreatic fistula
Causes of HAGMA
Methanol
Uremia
DKA
Paraldehyde
Isoniazid (INH)
Lactic acid
Ethanol/ethylene glycol
Salicylates
Compensation for metabolic acidosis
PCO2 = 1.5 (HCO3) + 8
Compensation for metabolic alkalosis
PCO2 = 40 + 0.7 (change in HCO3)
Compensation for respiratory acidosis
Acute: 1 HCO3 for every 10 CO2
Chronic: 3.5 HCO3 for every 10 CO2
Compensation for respiratory alkalosis
Acute: 2 HCO3 for every 10 CO2
Chronic: 5 HCO3 for every 10 CO2
Delta/delta
Change in AG / change in HCO3
> 2 = HAGMA + metabolic alkalosis
< 1 = HAGMA + NAGMA
1-2 = HAGMA
Acid base disturbance with cirrhosis and progesterone (pregnancy, OCP)
Respiratory alkalosis
Metabolic alkalosis + Ur Cl < 15
Chloride responsive
Volume depleted
Cl and HCO3 absorbed by kidneys
Remote diuretics
Volume depletion
Vomiting
NGT aspiration
Exogenous alkali
Metabolic alkalosis + Ur Cl > 15
Chloride unresponsive
Volume expanded
H lost but HCO3 not lost
Cl lost and HCO3 absorbed by kidneys
Diuretics
Recent high BP.
Hyper aldosteronism.
Cushing’s syndrome.
Licorice ingestion
Liddle’s syndrome.
Low/Normal BP
-hypomagnesemia
–hypokalemia.
–Bartter syndrome.
–Gitelman syndrome.
Decreased transportation, defect in ascending loop of Henle
Hypokalemia.
Lowe BP
Ur Cl > 15
Metabolic alkalosis
Similar to furosemide
Bartter syndrome
Decreased transportation defect in distal tubule.
Hypokalemia
Low BP.
Ur Cl > 15
Metabolic alkalosis
Increase uric acid
Increase Ca
Similar to thiazides
GItelman syndrome
Increased (aldosterone independent) transport defect and distal tubule
Hypokalemia
High BP
Ur Cl > 15
Metabolic alkalosis
Similar to hyperaldosteronism and licorice ingestion
Liddle’s syndrome
HAGMA + rectangular shaped calcium oxalate crystals
Ethylene glycol
(Aka antifreeze)
Management for osmolar gap
< 20 = supportive
> 20 = fomepizole
> 50 = HD + fomepizole
Increased Ur Cl
Diarrhea.
Ureterosigmoidostomy
Decreased Ur Cl
RTA
Early kidney disease
End stage kidney disease
Urine anion gap
UrNa + UrK - UrCl
Positive UAG
RTA
Negative UAG
Diarrhea (GI losses)
Defect in reabsorption of HCO3
+/- stone
Hypokalemia
Fanconi
Acetazolamide 
Topiramate
Proximal (Type 2) RTA
Defect in H & K excretion
No stones
Hyperkalemia
Ur pH < 5.5
Hypoaldosteronism
DM
Type 4 (hypoaldosterone) RTA
Defect in H excretion
+ stones (CaPO4)
Hypokalemia
Ur pH > 5.5
SLE
Sjogren
Amphotericin B
Classic distal (type 1) RTA
Daily requirement for sodium
3 mEq/kg/day
Causes of Hypernatremia
Sodium excess:
-improper mixing a formula (not enough water)
-Ingestion of sea saltwater
-Excessive sodium bicarb after resuscitation
-Breastmilk with excess of sodium
-Iatrogenic
Water deficit
-DI
-Diarrhea
Dilute urine
Hypernatremia
X-linked
Fails to respond to exogenous vasopressin
Nephrogenic DI
Causes of hyponatremia
Loss of sodium
Increased water
-polydipsia
-SIADH
Causes of SIADH
Trauma
Brain infection
Pulmonary disorders
Endocrine disorders
Vincristine
Cyclophosphamide
Carbamazepine
Post-op
Hyponatremia
Elevated BP
Decreased UOP
Elevated Urine Na (> 25 mEq/L)
Normal renal function
SIADH
Management of SIADH
Fluid restriction
Lasix
Hypertonic saline (Na < 120)
Demeclocycline (blocks effects of ADH on kidneys. Only indicated in > 8 yo)
Lithium (blocks effects of ADH on kidneys)
Normal Total body Na
Urine Na high
Dilutional hyponatremia
Increased UOP
High Urine Na
Cerebral salt wasting
Elevated TG and/or plasma protein
HypoNa
Pseudohyponatremia
Hypernatremia
Low urine Na
Low urine Osm (SG)
No urine Osm change post H2O deprivation
High urine Osm post DDAVP
Central DI
Hypernatremia
Low urine Na
Low urine Osm (SG)
No urine Osm change post H2O deprivation
No urine Osm change post DDAVP
Nephrogenic DI
Hyponatremia
Low urine Na
Low urine Osm (SG)
High urine Osm post H2O deprivation
High urine Osm post DDAVP
Psychogenic/polydipsia
Hyponatremia
High urine Na
High urine Osm (SG)
SIADH
Hyponatremia
High urine Na
High urine Osm (SG)
High urine Osm post DDAVP
Cerebral salt wasting
Cause Hypertonic Hyponatremia
Hyperglycemia
Cause of hypotonic isovolemic hyponatremia
SIADH
Cause of hypotonic hypovolemic hyponatrmia
Diarrhea (Ur Na < 20)
CSW (Ur Na > 20)
Daily requirement for potassium
2 mEq/kg/day
Causes of hypokalemia
Poor intake
Loss
-GI
-Renal
EKG changes in hypokalemia
Flatten T waves
ST depression
PVC
U wave
Replacing potassium
KCl 0.5-1 mEq/L/kg
Muscle weakness + prolonged QT
Hypocalcemia
Diarrhea
Prolonged PR or QT
Hypomagnesemia
Muscle weakness
No EKG changes
Hypoglycemia
Hyponatremia
Causes of Hyperkalemia
Excess intake
Renal failure
Hypoaldosteronism
Acidosis
Cell breakdown (pseudohyperkalemia)
EKG changes in hyperkalemia
Peaked T waves
Absent P waves
Wide QRS complex
Prolonged PR interval
V fib and asystole (electromechanical dissociation)
Treatment for hyperkalemia
Calcium gluconate/chloride
Bicarbonate/Beta-agonist
Insulin/glucose
Kayexalate
Diuretics/Dialysis
Potassium-pH relationship
For every 0.1 pH drop, K increases 0.6
For every 0.1 pH rise, K drops 0.6
Signs of mild (5%) dehydration
Tachycardia
Decreased tear production
Decreased UOP
Increased urine concentration
Volume down in 5% dehydration
50 mL/kg
Add to maintenance fluids
Signs of Moderate (10%) dehydration
Tachycardia
Sunken eyes
Poor skin turgor
Sunken fontanelle
Volume down in 10% dehydration
100 mL/kg
Add to maintenance fluids
Or give 20 mL/kg over 1 hr
Signs of severe (15%) dehydration
Shock
Delayed Cap refill
Volume down in 15% dehydration
150 mL/kg
Add to maintenance fluids
Or continuous 20 mL/kg boluses until improvement
Sodium replacement
(Desired Na - measured Na) x wt x 0.6
Add above to maintenance Na (3 mEq/kg/day)
Equals total Na replacement in 24 hr
Electrolyte abnormality in cystic fibrosis
Hypochloremia
Hyponatremia
Metabolic alkalosis
