Pediatric Nephrology

Fluids/Electrolytes in Pediatrics
Frank Tenney MD
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Fluid replacement therapy
Moderate dehydration ~7% (70 mL/kg)
Wt (15 kg) Water mL Na mEq K mEq
Maintenance 1250 37 25
Deficit (1000)      
ECF 75% 700 114  
ICF 25% 250   37
Additional Na*   63  
Total 2250 214 62
D5 0.45 NS + 30 mEq KCl / L at 100 ml/hr for 24 hrs
* Additional Na (135-128) x 15 (wt in kg) x 0.6 (total body water = 60% of body wt) = 63

 

Revised Rehydration Therapy
Stepwise Approach
1 IV + oral route
  a. IV: 40 mL/kg NS or LR over 1-2 hr = 600 mL
  b. ORT
2 ORT - WHO formula (>= 60 mEq NaCl/L) IV + oral route
3 IV only
  a. 40 mL/kg NS or LR over 1-2 hr
  b. Additional bolus 10-20 mL/kg NS or LR to normalize cardiovascular signs, if needed
  c. Start maintenance fluids as above over 24 hrs. replace additinal Na and K if needed as above.

Indications for the prescription of intravenous fluids

I. Highest priority

•     a) Defend haemodynamics
•          1. Re-expand a severely contracted ECF volume
•
•          2. Prevent a fall in blood pressure when venous tone is low (e.g., anaesthesia)
•     b) Return the ICF volume towards normal
•          1. Acute hyponatraemia that is symptomatic
•          Infuse hypertonic saline to raise the PNa by 5 mM in 1–2 h
•
•          2. Chronic hyponatraemia with a seizure
•          Infuse hypertonic saline to raise the PNa by 5 mM, but maximum is 8 mM/day; a lower target should be set if the patient is malnourished or K-depleted
•          3. Chronic asymptomatic hyponatraemia
•          Raise the PNa by up to 8 mM/day, slower rate if the PK is low in a malnourished patient
•II. Moderate priority
• a) Re-expand a modestly contracted ECF volume
•     Replace ongoing losses
•     Avoid oliguria
•     Match estimated electrolyte-free water loss in sweat and in the GI tract

Recommendations

How to Select Optimal Maintenance Intravenous Fluid Therapy

•Establish normal blood pressure

•Repair deficit; replace ongoing losses•

IF Na<138, DO NOT infuse hypotonic fluid•

Do not infuse NS in absence of indication•

Examine [Na] before infusing >1-2 L hypotonic fluids•

Be aware of occult oral water intake (ice, pop)•

Be ever more cautious if pt is young or has small muscle mass (50% of body H20 in muscle)•

Hypotonic fluid rate should match daily loss of electrolyte-free water in sweat in pt with Na>138•‘

One-size fits all - normal saline’ is NOT the answer…•

Q J Med 2003; 96:601–610

 

 

 

CASE PRESENTATION
A 4-year-old boy weighing 15 kg presented with a 3-day history of vomiting, decreased appetite, and 2 days of nonbloody diarrhea. He was “warm to the touch” according to the parents, but no direct measurement of temperature was taken.An older sibling had had a similar illness 5 days prior to the onset of vomiting by the patient.


For the previous 2 days, the patient had ingested only water, apple juice, and non-cola soft drinks. The parents believed that his urine output had dropped but only in the previous 12 hours. The patient’s past medical history
and review of systems were unremarkable. He took no medications on a chronic basis, although acetaminophen in appropriate doses was used by the family “when the child felt warm” (2–3 times/day).


On physical examination, he was mildly irritable and appeared somewhat ncomfortable while sitting quietly on his parent’s lap. The oral temperature was 38.2◦C; blood pressure, 90/64 mm Hg while seated; heart rate, 120 beats/min; and respiratory rate, 24 reaths/min. His skin was warm without rashes or edema. The head, ears, eyes, nose, and throat revealed a somewhat dry oral mucosa
but no other abnormal findings. His neck was supple without significant lymphadenopathy or thyromegaly. Chest examination revealed normal lung sounds with no murmur. The abdomen was slightly distended and tympanic
with active bowel sounds and no organomegaly or masses. There was no costovertebral angle tenderness. The patient had very slight peri-anal redness; the rest of the genitourinary exam was normal. His joints were not
red, full, or tender, and he had full range of motion of his arms and legs.


Urinalysis revealed a specific gravity of 1.020; 1+ protein, and negative for blood, bilirubin, glucose, leukocyte esterase, and nitrate; trace ketones; 1 to 2 white blood cells/high-power field, and 1 granular cast. Blood studies disclosed: sodium, 128 mEq/L; potassium, 3.6 mEq/L; chloride, 98 mEq/L; bicarbonate, 18 mmol/L; serum creatinine, 0.7 mg/dL; and blood urea nitrogen, 26 mg/dL.


The parents were concerned because the child continued to vomit.

Pediatric hydration therapy: Historical review and a new approach. Kidney International, Vol. 67 (2005), pp. 380–388