Neonatal Fluid and Electrolytes Flashcards Preview

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Flashcards in Neonatal Fluid and Electrolytes Deck (127)
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What is the most abundant component of the human body?



How is water distributed in the body?

into two compartments: intracellular and extracellular fluid


What is extracellular water composed of?

interstitial and intravascular spaces; total amount of water outside the cell


what is intracellular water?

total amount of water inside the cell


What is the main solute of the ECW?

plasma proteins; affects the colloid osmotic pressure


How is total body water affected by GA?

total body water decreases over age; over the first trimester, it composes about 90% of total body wt; at 32 wks, 80% of total body wt; by term GA about 78% and by 1 yr of age, it is about 65%: the ratio of ICW:ECW ∆ as well, with ECW gradually decreasing


What determines osmolality?

determined by the total # of solute particles in a solution


What is the net result of the fact that cell membranes are completely permeable to H2O, but not to solutes?

H2O will shift from one compartment to another until the osmolality on both sides as the membrane is equal


What is the major determinant of osmolality?

serum Na concentration


What is the formula to predict the serum osmolality?

2(plasma Na) + BUN/ 2.8 + Glucose/ 18


Why do newborns normally lose 5-15% of their birthweight?

- at birth, their is an acute increase in the ECW as H20 and lytes shift from the IC space to the EC space
- this puts infants in a state of excess ECF
- this excess ECW is then lost through diuresis as the expanded ECF compartment ctx
- (can also be r/t circulating levels of hormones)


What is the expected degree of weight loss in a newborn?

PT: 15-20%
FT: 5-10%


What is the state of fetal nephrons before 34 weeks GA?

functional but immature


What happens to a FT baby's renal fx after delivery compared with a PT baby?

improves more than PT; term and preterm can dilute their urine
- reabsorption of Na, HCO3 and glucose is limited in the newborn


What is characteristic of a PT baby's renal fx?

- can dilute urine, (but are slower at it); when faced with a rapid fluid load they will have a delayed response resulting in fluid retention
- difficulty concentrating their urine


What is the effect of antenatal steroids on the renal system?

- a/w decreased insensible H2O losses
- less frequent incidence of hypernatremia
- earlier diuresis


What is ADH?

hormone released by the posterior pituitary in reponse to a variety of stimuli.
- ADH influences water balance by stimulating the kidneys to CONSERVE water
- in the absence of ADH, the distal tubules remain impermeable to water (restricting reabsorption) and fluid is released as urine


Why can't newborns efficiently concentrate their urine?

decreased responsiveness to ADH


What factors stimulate ADH release?

1) hypotension
2) hyperosmolality


What is the normal range of UOP in the neonate?

1-4mL/Kg/h; highest rate occurs during the physiologic reduction of ECF


What are insensible water losses?

defined as the non-measureable losses that occur through the skin and respiratory system; influenced by numerous factors


What is tranepidermal water loss?

occurs as body water diffuses through the immature epidermis and is lost to the atmosphere


What influences transepidermal water loss?

- increases with decreasing GA
- a major source of insensible H2O loss in the VLBW
- highest on dol 1 and decreases on subsequent days as barrier fx improves
- closely r/t relative ambient humidity


What skin features predisposed the PT infant to evaporative heat loss?

- poor keratinization
- high H2O content
- low subQ fat
- large surface area
- high degree of skin vascularity


What is the result of failure to account for TWL?

inaccurate calculation/ estimates of TF needs with resultant fluid and electrolyte imbalances


When does skin barrier fx improve?

improvement slows with decreasing GA, may take several weeks to allow for full development of the strateum corneum; skin maturation isn't influenced by antenatal steroids or by gender


what are other sources of fluid loss in the neonate?

gastric drainage, enterostomies, surgical wounds, and pleural fluid drainage


What is the estimated amt of fluid loss d/t respiratory?

roughly 0-10 mL/kg/d- r/t temp and humidity of inspired gases and to minute ventilation


What is the estimated amt of fluid loss d/t feces?

est to be 5mL/kg/d in the first wk of life, then increase to 10mL/kg/d


what are water balance factors affecting loss?

- GA (renal fx, skin, illness)
- radiant warmer
- hyperthermia
- phototherapy
- tachypnea
- inadequate humidification
- diuretics
- osmotic diuresis