Fluids and Electrolytes Flashcards
- Hyponatremia, hypochloremia
- High urine osmolality and sodium (> 25)
- Euvolemic/hypervolemic
- Elevated BP
- Low urine output, low BUN
SIADH
SIADH causes and treatment
- CNS/pulm disorders, hypothyroidism, glucocorticoid deficiency, carbamazepime, SSRI/TCA, vincristine, cyclophosphamide, surgery (post-op)
- Underlying problem is fluid retention not excretion of sodium
- Tx: Fluid restriction is first line - can do furosemide and hypertonic saline if needed (if Na is < 120), demeclocycline (if over age 8)
- *REMEMBER SIADH HAS LOW URINE OUTPUT**
- Hyponatremia
- High urine sodium (> 100)
- Elevated urine output
- Hypovolemic
Cerebral salt wasting
- Hyponatremia, hypochloremia
- Increased BUN and specific gravity
- Low urine sodium (< 10)
- Hypovolemic
Hyponatremic dehydration
Serum osmolality calculation
2Na + (BUN/2.8) + (Glucose/18)
Normal is 265-285
Acid base normal values
- Bicarb > 25 = metabolic alkalosis, < 25 = acidosis
- pCO2 > 40 = respiratory acidosis, < 40 = alkalosis
Pyloric stenosis electrolytes
Hypochloremic hypokalemic metabolic alkalosis
- High pH
- Low: Na, K, Cl
Anion gap calculation
Na - (Cl + Bicarb)
Normal is 8-12
Normal anion gap acidosis causes
USEDCARP:
- Ureterostomy
- Small bowel fistula
- Extra chloride
- Diarrhea (most common)
- Carbonic anhydrase inhibitor use
- Adrenal insufficiency
- Renal tubular acidosis
- Pancreatic fistula
RTA basic symptoms
- Failure to thrive, polyuria, constipation, metabolic acidosis with elevated chloride and normal anion gpa
Kidney Bicarb Function (Proximal vs Distal)
- Proximal tubule Boxes Bicarb Back in
- Distal tubules Arranges for Acid to leave
Type 1 (Distal) RTA
- Distal tubule is not properly excreting acid
- Urine will have a high pH (greater than 5.5) and can’t be acidified
Type 2 (Proximal) RTA
- Inability for proximal tubule to reabsorb bicarb with excess bicarb in the urine but distal tubule still excretes acid so urine pH is less than 5.5
Type 4 RTA
- Resistance to aldosterone so hyperkalemia
Causes of elevated anion gap acidosis
MUDPILES
- Methanol
- Uremia
- Diabetic ketoacidosis
- Paraldehyde
- Isoniazid
- Lactic acid from organic acidemias
- Ethanol/ethylene glycol
- Salicylates
Daily requirement of sodium
3 mEq/kg/d
Causes of hypernatremia
Na greater than 145
- Sodium excess: improper formula mixing, ingestion of sea saltwater, excessive sodium bicarb after resuscitation, breast milk with excessive sodium, iatrogenic
- Water deficit: DI, diarrhea
Hypernatremia complications
Water follows Na so shifts out of intracellular compartment and leads to increased extracellular volume –> pulmonary edema
DI labs
- Due to central (lack of ADH) or nephrogenic (resistant to i)
- Peeing a lot –> high serum osmolality with inappropriately dilute urine
Nephrogenic DI
- X linked (only in males)
- Dilute urine
- Fail to respond to exogenous vasopressin
Renal failure causing hyponatremia
- Increased fluid intake and decreased urine output
- Elevated creatinine, edema, urine Na > 20
- If oliguric and hemodynamically unstable give 20/kg isotonic fluids
Dilutional hyponatremia labs/treatment
- Due to water intoxication (polydipsia or excessive dilution of formula), hypotonic IV fluids, glucocorticoid deficiency, hypothyroidism
- Total body sodium is normal but urine Na is > 100
- Seizures can occur due to cerebral swelling
- Infants will have seizures, respiratory insufficiency, and hypothermia
Third spacing of fluids vs dilutional hyponatremia
- Urine Na is high in dilutional hyponatremia
- Urine Na is low in 3rd spacing of fluids
- 3rd spacing occurs after extensive surgery due to endothelial damage/leakage, hypoalbuminemia and low oncotic pressure
Causes of pseudohyponatremia
- Elevated triglycerides or glucose –> sodium level in circulation is really normal
- Edema (nephrotic syndrome) –> total sodium level is actually elevated
Daily requirement for potassium
2 mEq/kg/d
Symptoms of hypokalemia
- Muscle pain, weakness, paralysis, constipation and ileus or polyuria
- EKG changes: flattening of T waves, ST depression, PVCs, U wave
Electrolyte abnormalities with muscle weakness and EKG changes
- Hypocalcemia: prolonged QT interval
- Hypomangesemia: prolonged PR or QT interval, can also have diarrhea
EKG changes for hyperkalemia
Peaked T waves and then eventually absence of P waves and widened QRS complex
Treatment of hyperkalemia
C BIG K - Calcium - Beta agonist (albuterol) - Insulin - Glucose - Kayexelate Can also use lasix or sodium bicarbonate
Potassium shifts with alkalosis and acidosis
- Alkalosis: K moves to the IC fluid and H moves out resulting in lower serum potassium but total body potassium is unchanged
- Acidosis: H moves in and K moves out resulting in high measured serum potassium
5% dehydration symptoms and treatment
- Tachycardia, decreased tears, decreased urine output
- Down 50 mL/kg so add this to the normal maintenance rate –> give the first half over 8 hours and the remainder over the next 16 hours
10% dehydration symptoms and treatment
- Tachycarida, sunken eyes, poor skin turgor, sunken fontanelle
- Down 100 mL/kg so add this to normal maintenance rate –> give 20 mL/kg over an hour then take whatever is left and give half over the next 7 hours and the remainder over the next 16 hours
15% dehydration symptoms and treatment
- Shock, delayed cap refill time
- Down 150 mL/kg
- Give 20 mL/kg boluses until some clinical improvement then give half of what is left over the next 7 hours and remainder over the final 16 hours
Oral rehydration solutions
- Needs to include glucose so it can cross the microvilli of the GI tract
Sodium correct and CNS issues
- Low to High your Pons will Die - correcting hyponatremia too fast will lead to pontine demyelination
- High to Low your Brain will Blow - correcting hypernatremia too fast will lead to cerebral edema
Hyponatremic dehydration symptoms and treatment
- Can present with seizures, often are more symptomatic (poor skin turgor)
- Rehydration: NS boluses, if not improving then can give hypertonic saline
- (Desired sodium - measured sodium) x weight x 0.6 –> add that to maintenance sodium (3 mEq/kg/d) and that is how much you need to replace over 24 hours
Hypernatremic dehydration symptoms and treatment
- Irritable, lethargic, doughy skin, high pitched cry, seizures
- Water tends to go into the ECF so clinically they don’t look dehydrated but you should assume 10% dehydration
- Intracellular dehydration can lead to shrinkage of brain cells, tearing of bridging blood vessels, and intracranial hemorrhage
- Correct the sodium SLOWLY (over 2-3 days), no more than 10-12 mEq change per day
- Hypernatremia, hyperchloremia
- Elevated BUN
- Decreased specific gravity
Diabetes insipidus
Electrolyte changes with loop and thiazide diuretics
- Metabolic alkalosis
- Hyponatremia
- Hypochloremia
- Hypokalemia
- Hyperuricemia
