Nephrology Flashcards by Sam Biniazan

Serum osmolality equation

2Na + BUN/2.8 + Glucose/18

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Leading cause of metabolic acidosis in children

Diarrhea

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Electrolyte derangement in pyloric stenosis

Hypochloremia
Hypokalemia
Hyponatremia
Metabolic alkalosis

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Anion gap

Na - (Cl + HCO3)

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Most common cause of NAGMA in children

Diarrhea

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Causes of NAGMA

Ureterostomy
Small bowel fistula
Extra chloride
Diarrhea
Chronic diuretic use
Adrenal insufficiency
RTA
Pancreatic fistula

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Causes of HAGMA

Methanol
Uremia
DKA
Paraldehyde
Isoniazid (INH)
Lactic acid
Ethanol/ethylene glycol
Salicylates

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Compensation for metabolic acidosis

PCO2 = 1.5 (HCO3) + 8

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Compensation for metabolic alkalosis

PCO2 = 40 + 0.7 (change in HCO3)

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Compensation for respiratory acidosis

Acute: 1 HCO3 for every 10 CO2

Chronic: 3.5 HCO3 for every 10 CO2

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Compensation for respiratory alkalosis

Acute: 2 HCO3 for every 10 CO2

Chronic: 5 HCO3 for every 10 CO2

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Delta/delta

Change in AG / change in HCO3

> 2 = HAGMA + metabolic alkalosis
< 1 = HAGMA + NAGMA
1-2 = HAGMA

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Acid base disturbance with cirrhosis and progesterone (pregnancy, OCP)

Respiratory alkalosis

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Metabolic alkalosis + Ur Cl < 15

Chloride responsive
Volume depleted
Cl and HCO3 absorbed by kidneys

Remote diuretics
Volume depletion
Vomiting
NGT aspiration
Exogenous alkali

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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.

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Decreased transportation, defect in ascending loop of Henle
Hypokalemia.
Lowe BP
Ur Cl > 15
Metabolic alkalosis
Similar to furosemide

Bartter syndrome

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Decreased transportation defect in distal tubule.
Hypokalemia
Low BP.
Ur Cl > 15
Metabolic alkalosis
Increase uric acid
Increase Ca
Similar to thiazides

GItelman syndrome

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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

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HAGMA + rectangular shaped calcium oxalate crystals

Ethylene glycol
(Aka antifreeze)

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Management for osmolar gap

< 20 = supportive
> 20 = fomepizole
> 50 = HD + fomepizole

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Increased Ur Cl

Diarrhea.
Ureterosigmoidostomy

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Decreased Ur Cl

RTA
Early kidney disease
End stage kidney disease

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Urine anion gap

UrNa + UrK - UrCl

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Positive UAG

RTA

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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