See also "Fluid and Electrolytes"

I. Children's kidneys have less concentrating ability and maximum GFR than adults

II. If documented recent weight, can be helpful in determining fluid losses

III. Diagnosing and determining degree of volume depletion:

  1. Decreased level of consciousness
  2. Decreased skin turgor
  3. Elevated respiratory rate
  4. Prolonged capillary refill
  5. Decreased BP (only decreased in extreme volume depletion)
  6. Decreased urine output (sensitive but nonspecific)
  7. Laboratory data: serum HCO3 >15-17mEq/L is associated with absence of severe dehydration in children with gastroenteritis (JAMA 291:2746, 2004--AFP)
  8. Not reliable for diagnosis per a systematic review (JAMA 291:2746, 2004-AFP): Cool extremities, absence of tears, weak pulse, "sunken" eyes, dry mucous membranes, sunken appearance to fontanel(s) (if open), elevated heart rate

IV. Isotonic volume depletion (Na 130-150)-60% of cases; causes include diarrhea, vom, vasting

V. Hypertonic volume depletion (Na >150)-25% of cases; don't look as sick b/c circulating volume preserved by diffusion or water from intracellular compartment; caused by isotonic loss with hypertonic replacement

VI. Hypotonic volume depletion (Na < 130)-15% of cases; causes by isotonic loss with hypotonic replacement; also cystic fibrosis and "adrenogenital sd." (?)

VII. Deciding on fluid replacement:

  1. Maintenance: 100-50-20 rule vs. BSA rule (1500-1600 ml/m2/d)
  2. Replacement of static deficits
  1. 10-200ml/kg over 1h of ISOTONIC
  2. Rest of replacement based on established degree ot H2O/electrolyte losses; 0.5 of deficit in 1st 24h; 0.25 in next 8; 0.25 in next 16
  1. Consideration of ongoing losses: diarrhea is hypotonic; sweat in CF is hypertonic

VIII. Normal range for K in full-term neonates in 5.5-6.5!; can be higher in preemies; Cr should be about 0.3 in full-term neonates