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Title: Fluid and Electrolytes: TUSM III Pediatric Clerkship Lecture Series


1
Fluid and ElectrolytesTUSM III Pediatric
Clerkship Lecture Series
  • Margaret Rounds, MD
  • Baystate Medical Center
  • Departments of Pediatrics
  • July 26, 2004

2
Objectives
  • Understand maintenance fluid therapy
  • Fluid composition
  • Fluid rate
  • Calculate fluid therapy in dehydration
  • Understand differences in fluid therapy for
    hyponatremia and hypernatremia

3
Parenteral Fluid Therapy
  • IVF is a basic component of the care of
    hospitalized infants and children
  • Fluid and electrolyte problems can be
    challenging, but can be tamed by an organized
    approach
  • Useful to consider separately the following
    questions
  • How much? or volume and rate
  • What kind? or electrolyte constitution

4
Parenteral Fluid Therapy
  • IVF therapy is tailored to address differing
    clinical needs
  • Maintenance
  • Deficit
  • Ongoing losses

5
Maintenance Fluid
  • Metabolism creates two by-products which must be
    actively eliminated to maintain homeostasis
  • Heat dissipated by insensible losses from skin
    and lung
  • Solute waste products of metabolism excreted
    into the urine

6
Maintenance Fluid
  • Basal Metabolic Rate does not directly relate to
    body weight
  • BMR is much higher in the neonate than the adult
    and the transition is not linear
  • As a result, adults need less fluid and
    electrolytes than children per kg of bodyweight

7
Methods of Estimating Maintenance Fluids
  • Methods of estimating basal or maintenance fluid
    requirements
  • Body Surface Area
  • Need to know height and weight, requires table,
    does not allow for deviations from normal
    activity
  • Basal or Calorie Expenditure Method
  • Requires a table, involves calculations, permits
    correction for changes in activity or injury,
    drier
  • Holliday-Segar System
  • Easy to remember, does not require table or
    difficult calculations, does not allow for
    deviations from normal activity

8
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9
Holliday-Segar Formula
  • How does it work?
  • Estimates that 1 kcal of energy requires 1 cc of
    fluid to maintain homeostasis
  • Derives from fact that for each 100 kcal of
    energy expended, 50 cc of fluid are lost through
    the skin and airways, and 55 to 65 cc of fluid
    are required to generate an isosmotic urine (300
    mOsm/L)
  • Heat dissipation and solute excretion each
    represent roughly 50 of maintenance needs
  • Anuric patients have one-half maintenance needs

10
Maintenance Electrolytes
  • No electrolytes are lost in sweat or exhaled
    water vapor all electrolyte losses are urinary
  • Thus, anuric patients have no maintenance sodium
    or potassium needs
  • Since sodium and fluid requirements are based on
    BMR, the ratio of electrolyte to water is fixed
    and maintenance fluid requirements are the same
    for all patients (regardless of age)
  • (D5 0.2 NS 20 mEq/L of K)

11
Fluid Composition
12
Maintenance Electrolytes
  • Estimated electrolyte needs
  • Na 3meq/100ml 30 meq/L
  • Cl 2 meq/100ml 20 meq/L
  • K 2 meq/100 ml 20 meq/L
  • Maintenance fluid composition comes to D5 0.2NS
    with 20 meqKCl/L

13
Clinical Practice
  • Why do we give D5 0.45 NS with 20 K to kids over
    10 kg?
  • ADH is increased during illness
  • Many have diarrhea/vomiting as ongoing losses
  • Why do we give D5 0.2 NS with 20 K to kids under
    10 kg?
  • The kidney continues to mature after birth, and
    has decreased concentrating ability

14
Deficit Fluid
  • Definition Amount of fluid lost before treatment
    is begun
  • One-time estimate additional losses after
    therapy is begun are considered on-going losses
  • Methods
  • Weight loss due to acute illness
  • Fluid deficit (L) Preillness weight (kg)
    current weight (kg)
  • Estimation of dehydration
  • Fluid deficit (L) dehydration x Preillness
    weight (kg) / 100
  • Clinical estimates of weight loss

15
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16
Deficit Electrolytes
  • Sodium usually in pediatrics, losses are
    gastrointestinal or due to a relatively short
    period of decreased oral intake
  • approximated by 0.45 NS
  • Potassium deficit replacement is based on rate
    of safe replacement and not amount since danger
    of hyperkalemia is greater than hypokalemia
  • Add 20 mEq potassium/L after UOP is established
  • Potassium infusion rate should not exceed 1
    mEq/kg/hour unless in monitored setting

17
Ongoing losses Fluid and Electrolytes
  • Fluid abnormal losses that occur after the
    one-time determination of a deficit
  • Diarrhea, vomiting, NG aspirates, polyuria
  • Measured and replaced cc for cc
  • Electrolytes
  • Consult tables for electrolyte composition of
    on-going losses
  • GI losses 0.45 NS
  • Transudates 0.9 NS
  • Radiant losses sodium free

18
Overview of Parenteral Rehydration Strategy
  • Phase I (immediate) If the patient is
    hemodynamically unstable or in shock, one or
    more boluses of 20 cc/kg isotonic fluid (0.9NS
    or LR) should be given in the first 30 minutes
  • Phase II (deficit, maintenance, ongoing fluid
    replacement)
  • Calculate fluid deficit
  • Calculate maintenance fluid
  • Give ½ of deficit therapy maintenance over
    first 8 hours and remainder of deficit
    maintenance over next 16 hours (or replaced
    deficit over 1st 8 hrs and 24 hrs of maint fluids
    over next 16 hrs.)
  • Adjust above based on consideration of ongoing
    losses likely to be encountered

19
Case 1
  • A 5 month male old infant is brought to your ER
    with 4 day history of vomiting, diarrhea, and
    reduced oral intake. UOP is markedly reduced. On
    exam, the infant is fussy but consolable. He
    pushes you away when you try to examine him.
    Weight is 6.3 kg (5-25th ile), BP is 90/55 (50th
    ile), HR is 190 (gt95th ile). The fontanelle is
    slightly sunken and his skin turgor is
    diminished. The cardiopulmonary, abdominal, and
    neurologic exams are normal. He has stopped
    vomiting but refuses to drink.

20
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21
Case 1 Solution ACombined Deficit/Maintenance
  • Bolus 140 cc (20 cc/kg) of NS given for
    hemodynamic instability
  • Deficit Fluid
  • No preillness weight, so must estimate
  • Oliguria, tachycardia, no shock ? 10 dehydrated
  • Deficit 10 x 7kg wt loss / 100 0.7L or 700cc
  • (alternatively 10cc/kg weight loss x 7 kg 700
    cc)
  • Maintenance Fluid
  • Holliday-Segar 4 cc/kg for first 10 kg 7 kg x
    4 cc/kg 28 cc/hr
  • Note Should use preillness weight to calculate
    deficit (6.3 kg x 100)/(100-10) 7 kg

22
Case 1 Solution A Combined Deficit/Maintenance
  • First 8 hours
  • Maintenance
  • 28 cc/hr x 8 hours 224 cc
  • In theory D5 0.2 NS 20 mEq KCl/L
  • In practice D5 0.45 NS 20 mEq KCl/L
  • Half Deficit 700/2 350 cc of 0.45 NS
  • Total Fluid 574 cc/ 8 hour 71.8 cc/hr
  • IVF 75 cc/hr of D5 0.3 NS 20 mEq KCl/L
  • In practice, we would give D5 ½ NS 20 K
  • ADH is increased
  • We usually choose between ¼ NS and ½ NS

23
Case 1 Solution A Combined Deficit/Maintenance
  • Next 16 hours
  • Maintenance
  • 28 cc/hr x 16 hours 448 cc
  • In theory D5 0.2 NS 20 mEq KCl/L
  • In practice D5 0.45 NS 20 mEq KCl/L
  • Half Deficit 700/2 350 cc of 0.45 NS
  • Total Fluid 798 cc/ 16 hour 49.9 cc/hr
  • IVF 50 cc/hr of D5 0.45 NS 20 mEq KCl/L

24
Case 1 Solution B Sequential Deficit/Maintenance
  • Bolus 140 cc (20 cc/kg) of 0.9 NS
  • First 8 hours
  • Remainder of Deficit 20 cc/kg bolus represents
    2 of body weight. Since infant was 10
    dehydrated, the remainder of deficit after the
    bolus is 8 (or 80 cc/kg). This can be replaced
    over next 8 hours at 1/hr.
  • 1/hr 10 cc/kg/hr 70 cc/hr
  • IVF (Deficit) D5 0.45 NS 20 mEq/L KCl

25
Case 1 Solution B Sequential Deficit/Maintenance
  • Next 16 hours
  • Days worth of maintenance fluid is then provided
    in next 16 hours
  • 4 cc/kg/hr x 7 kg x 24 hours 672 cc Fluid
  • 672 cc/16 hours 42 cc/hr
  • IVF (Maintenance)
  • In theory D5 0.2 NS 20 mEq/L KCl
  • In practice D5 0.45 NS 20 K

26
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27
Monitoring Effectiveness of Parenteral Therapy
28
Oral Rehydration Therapy
  • Indications mild to moderate dehydration
  • Contraindications shock, severe dehydration,
    intractable vomiting, coma, gastric distension
  • Method give 5-10 cc of ORT q 5-10 minutes
  • Fluids Cerealyte, Pedialyte, Naturalyte,
    Rehydralyte, WHO/UNICEF ORS (One teaspoon salt, 8
    teaspoon sugar, 1 liter water)
  • Avoid soda, juice, gatorade, jello
  • Lack sufficient sodium and potassium, are often
    hyperosmolar, can perpetuate diarrhea

29
Disorders of Sodium
  • Serum Sodium gt Osmolality lt Water
  • Regulated by thirst , ADH, renal water handling
  • A disruption in water balance is manifested as an
    abnormality in serum sodium
  • Sodium is a functionally impermeable solute, so
    it contributes to tonicity and induces water
    movement across membranes
  • Hypernatremia hyperosmolar (hypertonic)
    Hyponatremia hyposmolar (hypotonic)

30
  • Hypernatremia Serum Sodium gt 145 mmol/L
  • Hypernatremia represents a deficit of water in
    relation to the bodys sodium stores
  • Net water loss
  • Common
  • Hypertonic sodium gain
  • Uncommon
  • Usually iatrogenic

31
Hypernatremia Clinical Manifestations
  • Related to CNS dysfunction sequelae are
    prominent when the increase in serum sodium is
    rapid or large
  • Affects the very young or very old
  • Infants hyperpnea, muscle weakness,
    restlessness, high-pitched cry, insomnia,
    lethargy, or coma. Seizures are uncommon.
  • Elderly often asymptomatic until Na gt 160

32
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33
Hypernatremia Management
  • Approach
  • Identify Cause
  • Correct Hypertonicity
  • Rapid Correction
  • Improves prognosis in patients in whom
    hypernatremia developed acutely (sodium loading)
  • Correct serum sodium by up to 1 mmol/L/hr

34
Hypernatremia Management
  • Slow Correction
  • Prudent in patients with hypernatremia of longer
    or unknown duration
  • Correct sodium by 0.5 mmol/L/hr or 10 mmol/d with
    goal of 145 mmol/L
  • Others suggest adding the calculated fluid
    deficit to maintenance fluid requirements and
    giving over 48 hours
  • IVF
  • Only hypotonic fluids are appropriate unless
    frank circulatory collapse exists
  • The more hypotonic the infusate, the lower the
    required volume to correct the hypertonicity, and
    the lower the risk of cerebral edema

35
Hypernatremia Management
  • Rate of infusion is calculated using the Madias
    Formula which estimates the change in serum
    sodium caused by 1 liter of any infusate. The
    required volume, and thus rate, is determined by
    dividing the change in serum sodium desired for a
    given period of time by the value obtained from
    Madias formula.

36
Case 2
  • A 1 week old female neonate is admitted to the
    PICU after increasing lethargy and difficulty
    with breastfeeding. Her birthweight was 3.8 kg.
    Her admission weight is 3.3 kg. On exam, the
    infant is difficult to arouse. BP is 72/62 (75th
    ile), HR is 120 (50th ile), RR is increased at
    60. The PE is unrevealing except for hypotonia
    and decreased level of consciousness. The nurse
    informs you the sodium is 165 mmol/liter.

37
Case 2 Solution A
  • Bolus? no
  • Deficit Fluid
  • Deficit 3.8 kg 3.3 kg 0.5 kg or 500 cc
  • Maintenance Fluid
  • Holliday-Segar 4 cc/kg for first 10 kg 3.8 kg x
    4 cc/kg 15.2 cc/hr
  • 48 hours needs
  • Deficit 500 cc of 0.45 NS
  • Maintenance 15 cc/hr x 48 hr 720 cc of D5 0.2
    NS 20 mEq KCl/L
  • Total Fluid 500 cc 720 CC 1200 cc/ 48 hour
    25 cc/h
  • IVF 25 cc/hr of D5 0.3 NS 20 mEq KCl/L

38
Case 2 Solution B
  • Deficit (Madias Formula)
  • TBW (0.8 x 3.8kg) 3 L
  • Retention of 1 L of 0.2 NS will reduce the serum
    sodium by 40 (34-195/31)
  • The goal of therapy is to reduce the serum sodium
    by 20 mmol/L in 48 hours. Therefore, 20/40 is 0.5
    L or 500 cc of fluid is required.
  • 48 hour needs
  • Deficit 500 cc of D5 0.2 NS
  • Maintenance 3.8 kg x 4 cc/kg 15.2 cc/hr x 48
    hr 720 cc of D5 0.2 NS 20 mEq KCl/L
  • Total Fluid 500 cc 720 CC 1200 cc/ 48 hour
    25 cc/h
  • IVF 25 cc/hr of D5 0.2 NS 20 mEq KCl/L

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40
Hyponatremia
  • Serum Sodium lt 136 mmol/L
  • Hypotonic hyponatremia results from an excess of
    water in relation to existing sodium stores,
    which can be decreased, normal, or increased.
  • Impaired renal water excretion
  • common
  • Excess water intake
  • uncommon

41
  • Adults thiazide diuretics, SIADH, polydipsia,
    and TURP
  • Children GI fluid loss, ingestion of dilute
    formula, accidental ingestion of water, and
    multiple tap water enemas.

42
Hyponatremia Clinical Manifestations
  • Related to CNS dysfunction sequelae are
    prominent when the decrease in serum sodium is
    rapid or large
  • Symptoms Headache, nausea, vomiting, muscle
    cramps, lethargy, restlessness, disorientation,
    and depressed reflexes
  • If Na lt 125 mmol/L seizure, coma, brain damage,
    herniation, and death

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44
Hyponatremia Management
  • Symptomatic Hypertonic saline therapy (can be
    combined with furosemide to limit expansion of
    ECF)
  • Correct 1-2 mmol/L/hour x several hours if
    severly symptomatic
  • Target for increase in serum sodium of no more
    than 8 mmol/d to prevent osmotic demyelination
  • Asymptomatic Fluid therapy is guided by Madias
    Formula

45
Hyponatremia Management
  • Rate of infusion is calculated using the Madias
    Formula which estimates the change in serum
    sodium caused by 1 liter of any infusate. The
    required volume, and thus rate, is determined by
    dividing the change in serum sodium desired for a
    given period of time by the value obtained from
    Madias formula.

46
Case 3
  • A 12 year old male is found unresponsive at the
    bottom of a swimming pool. He is resuscitated in
    the field and on arrival to the ER is intubated
    and ventilated but has a spontaneous pulse. In
    the trauma room, he develops generalized
    tonic-clonic seizures. He is loaded with
    phenytoin. His stat sodium then returns at 110
    mmol/L. His weight is 45 kg, BP is 100/70
    (normal), HR is 100 (normal). On exam, he is
    unresponsive and his right pupil is sluggish.

47
Case 1 Solution
  • Initial management is to prevent cerebral edema
    and herniation TBW 0.6 x 45 kg 27 L
  • Madias Formula Retention of 1 L of 3 NS will
    increase the serum sodium by 14.4 mmol
    (513-110)/(271)
  • The goal of therapy is to increase the serum
    sodium by 5 mmol/L in 3 hours. Therefore, 5/14
    210 cc of fluid is required.
  • IVF 210 cc/3 hr 70 cc/hr of 3 NS x 3 hours.

48
References
  • Adrogue, HJ and NE Madias. Hypernatremia. New
    England Journal of Medicine. 2000 342(20)
    1493-1499.
  • Adrogue, HJ and NE Madias. Hyponatremia. New
    England Journal of Medicine. 2000 342(21)
    1581-1589.
  • Choukair, MK. Fluids and Electrolytes. In
    Siberry GK and R. Iannone, ed. The Harriet Lane
    Handbook. 15th ed. St. Louis, MO Mosby 2000
    229-240.
  • Roberts, KB. Fluid and Electrolytes Parenteral
    Fluid Therapy. Pediatrics in Review. 2001
    22(11) 380-387.
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