Fluid and Electrolyte Management

Fluid and Electrolyte Management
Tara Conway Copper
Carrie Nalisnick
  • This chapter serves as a quick reference for fluid and electrolyte abnormalities in children, focusing on definitions, differential diagnosis, common presentations, and basic approach to management.
FLUID MAINTENANCE
  • Maintenance fluid needs are based on insensible losses from the skin and respiratory tract and sensible losses from urine and stool.
  • Maintenance intravenous fluids (IVF) are provided when patients cannot or will not take fluid orally. They are not a substitute for fluids already lost; repletion fluids should be provided in addition to maintenance fluids for this purpose. The clinician should also consider ongoing fluid losses when providing supplemental IVF.
  • Calculation of maintenance IVF (in mL/hr):
    (Body Surface Area (BSA) × 1, 500 mL) ÷ 24 hr BSA m2 (Mosteller formula) = [check mark] [(Height (cm) × Weight (kg)) ÷ 3, 600]
  • This is usually provided with IVF containing 5% dextrose and 77 mEq/L of sodium (which is 0.45% sodium chloride or ½ normal saline).
DEHYDRATION AND HYPOVOLEMIA
  • Dehydration is common in children, and is most commonly due to gastroenteritis, with losses in excess of retained intake.
  • Dehydration may be isotonic, hyponatremic, or hypernatremic, and the history will suggest the etiology. The following section discusses isotonic dehydration.
    • Assessment of dehydration
      Percent dehydration = (preillness weight – current weight)/preillness weight
  • Preillness weight is often not accurately known. Table 3-1 gives physical examination findings that allow estimation of the degree of dehydration.
  • Management
    • Mild dehydration: 3%-5%
      • Oral rehydration therapy (ORT): 50 mL/kg plus replacement of ongoing losses with oral rehydration solution (ORS) over 4 hours
      • If vomiting, give small frequent amounts (5-10 mL) every 1-2 minutes to give total volume of ORS calculated over 4 hours.
      • Reassess hydration status and ongoing losses every 2 hours.
      • Serum electrolyte measurement is not necessary for mild and moderate dehydration when isotonic dehydration is suspected.
    • Moderate dehydration: 6%-9%
      • Attempt ORT with 100 mL/kg plus replacement of ongoing losses with ORS over 4 hours.
      • If ORT fails, then begin intravenous (IV) rehydration with normal saline (NS), with a goal of replacing the fluid deficit over 4 hours.
    • Severe dehydration: ≥10%
      • Severe dehydration is a medical emergency and results in shock.
      • Obtain serum electrolytes and glucose.
      • Treat hypoglycemia (glucose < 60 mg/dL) and electrolyte abnormalities.
      • Give a rapid IV bolus of 20 mL/kg normal saline and repeat as necessary to improve perfusion.
      • Once pulse, perfusion, and mental status return to normal, ORT can begin, with a goal of replacing the remaining deficit over 2-4 hours.
  • Replacement of ongoing losses
    • Consider the patient’s underlying source of fluid loss when choosing the composition of replacement fluids. For example, fecal losses contain more water than sodium (35-60 mEq Na/L), so ½ NS would be an appropriate replacement fluid.
  • Inpatient management indications include: intolerance of ORS (intractable vomiting, refusal, or inadequate intake), inability to provide adequate care at home, acute bloody diarrhea, concern for complicating illnesses, severe dehydration, lack of follow-up, progressive symptoms, young age, or diagnostic uncertainty.
  • See Table 3-2 for the composition of common oral fluids compared with the WHO recommendations for the composition of ORS.
TABLE 3-1 Symptoms Associated with Dehydration

Symptom

Minimal or no dehydration (<3% loss of body weight)

Mild-to-moderate dehydration (3%-9% loss of body weight)

Severe dehydration (>9% loss of body weight)

Mental status

Well; alert

Normal, fatigued or restless, irritable

Apathetic, lethargic, unconscious

Thirst

Drinks normally; might refuse liquids

Thirsty; eager to drink

Drinks poorly; unable to drink

Heart rate

Normal

Normal to increased

Tachycardia, with bradycardia in most severe cases

Quality of pulses

Normal

Normal to decreased

Weak, thread, or impalpable

Breathing

Normal

Normal; fast

Deep

Eyes

Normal

Slightly sunken

Deeply sunken

Tears

Present

Decreased

Absent

Mouth and tongue

Moist

Dry

Parched

Skin fold

Instant recoil

Recoil in <2 sec

Recoil in >2 sec

Capillary refill

Normal

Prolonged

Prolonged; minimal

Extremities

Warm

Cool

Cold; mottled; cyanotic

Urine output

Normal to decreased

Decreased

Minimal

Source: Adapted from Duggan C, Santosham M, Glass RI. The management of acute diarrhea in children: oral rehydration, maintenance, and nutritional therapy. Morb Mortal Wkly Rep 1992;41(No. RR-16):1-20; World Health Organization. The Treatment of Diarrhea: A Manual for Physicians and Other Senior Health Workers. Geneva, Switzerland: World Health Organization, 1995. Available at http://www.who.int/childadolescent-health/New_Publications/CHILD_HEALTH/WHO.CDR.95.3.htm.

TABLE 3-2 Composition of ORS Compared with Common Oral Fluids

ORS

Carbohydrate (mmol/L)

Sodium (mmol/L)

Potassium (mmol/L)

Chloride (mmol/L)

Osmolarity (mOsm/L)

WHO recommendations

Should equal Na, but not > 110

60-90

15-25

50-80

200-310

WHO ORS (2002, reduced osmolarity)

75

75

20

65

245

WHO ORS (1975)

111

90

20

80

311

Pedialyte

139

45

20

35

250

Apple juice

667

0.4

44

45

730

Gatorade

323

20

3.2

11

299

Soda

622

1.6

N/A

N/A

650

Adapted from MMWR Recommendations and Reports: Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy.

ELECTROLYTE ABNORMALITIES
Hypernatremia
Definition
  • Hypernatremia is defined as a serum sodium >150 mEq/L.
Etiology
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Jun 5, 2016 | Posted by in PEDIATRICS | Comments Off on Fluid and Electrolyte Management

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