Fluid And Electrolytes Flashcards
Total body water
Decreases with increasing gestational age
Diuresis in first 3 days from extracellular fluid compartment (ECF)
Increases insensible water loss (IWL)
Lower GA and BW Increased RR Ambient temp above NTE Fever Radiant warmer use Activity
Decreased IWL
High relative humidity (esp <28 week) Heat shield/double walled incubators Plastic blankets Clothing Humidified inspired gases
Osmolality
Smaller molecules more osmotic than larger ones
Na > gluc > albumin
Stimulus of ADH secretion via osmoreceptors in hypothalamus
Electrolytes in stomach fluids
Na 20-80
K 5-20
Cl 100-150
Electrolytes in small intestine fluids
Na 100-140
K 5–15
Cl 90-120
Electrolytes in bile
Na 120-140
K 5-15
Cl 90-120
Electrolytes from ileostomy
Na 45-135
K 3-15
Cl 20-120
Electrolytes in diarrhea
Na 10-90
K 10-80
Cl 10-110
Fractional excretion of sodium
Proportion of Na excreted based on how much serum is filtered by kidney
Decreases with increasing GA
Hypernatremia
Na > 150 Due to: - dehydration (decreased free water) - too much sodium - congenital decreased ADH (seen after 2-3 days, rare) - occasionally excess maternal Na
Hypernatremia and IVH
Hypernatremia over first several days after birth associated with severe IVH
Risk increased with concommitmenthyperglycemia
Hyponatremia
Na < 130 Due to: - overhydration (too much free water) - excess renal loss of sodium - SIADH - other losses - use of indomethacin (potentiates ADH effect)
Causes of hyperkalemia (K>7)
Sampling site Acidosis (Shifts K extracellular) Renal failure Adrenal insufficiency Excess intake Spironolactone
Treatment of hyperkalemia
Stop all K
Consider bicarb (K into cell)
Can give sodium polystyrene sulfonate (will increase Na)
Peritoneal dialysis
Exchange transfusion
Maintain normal ionized calcium to stabilize heart
Use of glucose and insulin shifts K into the cell, doesn’t lower total body K

Causes of hypokalemia (K<3.5)
Preterm infants with IUGR (DOL 1) Increased G.I. losses Renal losses Drugs (amphotericin, aminoglycosides, beta agonists) Restricted intake
Similar clinical signs, different EKG findings from hyperkalemia
Causes of hypocalcemia (Ca<8)
Early - abrupt cessation of transplacental Ca passage Elevated calcitonin Decreased PTH Decreased 25-OH vitamin D DiGeorge
Risk factors for hypocalcemia
Prematurity Infant of diabetic mother Perinatal stress/asphyxia Intrauterine growth restriction 22q11 abnormalities
Causes of hypercalcemia (Ca>11)
Increased administration of Ca
Low Phos
Elevated PTH
Elevated vitamin D
Risk factors for hypercalcemia
TPN
Therapeutic hypothermia (fat necrosis)
Maternal hypoparathyroidism
Williams syndrome
Hypophosphatemia
P < 4
Very common among preterm infants with IUGR
Worry about refeeding syndrome
When is antidiuretic hormone secreted?
- increased osmolality (osmoreceptors in hypothalamus)
- decreased plasma volume (pressure receptors in veins, atria, carotids)
Overall effect of ADH secretion?
Increases water reabsorption by kidney
Diabetes insipidus
Decreased ADH Nephrogenic or neurogenic Signs: - Polyuria - Hypernatremia - Increased thirst
Think about with holoprosencephaly or Septo optic dysplasia
SIADH
Increased ADH
Hyponatremia
Concentrated urine (Uosm > Sosm without dehydration)
Normal or hypervolemia
Diabetes insipidus treatment
Neurogenic - Desmopressin (DDAVP) = analog of ADH
Nephrogenic - hydrochlorothiazide increases proximal tubule reabsorption of sodium and water
Aldosterone
Mineralocorticoid made in zona glomerulosa of adrenal cortex
Can cross placenta
Increases reabsorption of Na and water and secretion of K
Simulates renal secretion of H
Feedback loop to pituitary to release ADH
Aldosterone stimulated by
Stretch receptors in atria of heart
Renin angiotensin aldosterone system
Hyperkalemia
Plasma acidosis
Hypoaldosteronism
Hypotension
Hyponatremia
Hyperkalemia
Metabolic acidosis
Seen in CAH, adrenal insufficiency

Hyperaldosteronism
Hypertension
Hypernatremia
Conn syndrome, Bartter syndrome
Extremely rare in neonates
Causes of metabolic acidosis
Lactic acidosis Acute renal failure Inborn errors of metabolism Toxins Diarrhea CAH TPN Renal tubular acidosis
Causes of metabolic alkalosis
Acid loss (vomiting, pyloric stenosis)
Diuretics (contraction alkalosis)
Compensation of chronic respiratory acidosis
Bartter syndrome (IUGR, polyuria, low K, low mag)
Exogenous bicarb
Increased aldosterone
Cystic fibrosis
When is nephrogenesis complete?
34 weeks gestation
Is urine concentrating ability increased or decreased at lower gestational ages?
Decreased
How do antenatal steroids help the kidneys concentrate urine better?
Increased Na/K-ATPase and Na/H exchanger
Clinical signs of hyperkalemia
Ileus
Muscle weakness
Cardiac arrhythmia
Where is antidiuretic hormone made?
Hypothalamus
Where is antidiuretic hormone stored?
Posterior pituitary
How does ADH affect renin secretion?
Decrease
How does ADH affect ACTH secretion?
Increase
What does ADH do to the distal tubules of the kidney?
Increases permeability
How does ADH affect V2 receptors?
Increase cAMP -> phosphorylation of aquaporin 2
How does ADH affect renal mesagial cells?
Contraction - remove debris from glomerular basement membrane
Management of SIADH
Water restriction
AVP receptor antagonist
What pathologies is SIADH seen with?
HIE
IVH
Pulmonary air leaks
What is the total body water in a newborn
75% of birth weight
What can cause a transudative effusion?
Congestive heart failure
Cardiac arrhythmias
Hypoalbuminemia
What can cause an exudative effusion?
Chylothorax
Meconium peritonitis
