fen basics
TRANSCRIPT
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PEDIATRIC FLUIDS
Katinka Kersten, MD
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ECF and ICF
Body has two fluid compartments
Extracellular fluid (ECF) space makes up 1/3 of ourbody fluids
Intracellular fluid (ICF) space makes up 2/3 of our bodyfluids
Extracellular space refers to fluids outside ourcells which may be interstitial fluid or plasma
Total body water = 0.6 X weight (kg) for childrenand adults and 0.78 X weight (kg) for neonatesand infants
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Approach to Fluid Calculations
1. Maintenance: Determined by a system:
a. Caloric expenditure method
b. Holliday-Segar methodc. Surface area method
2. Deficit: Determined by acute weight
change or clinical estimate
3. Ongoing losses: Determined by measuring
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Maintenance Fluids
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Caloric Expenditure Method
Based on understanding that water and
electrolyte requirements parallel caloric
expenditure but not body weight
Is effective for all ages, shapes, and clinical
states, many age based tables exist for
estimating caloric needs
Per 100 calories metabolized you need 100-
120 ml H2O, 2-4 mEq Na+
, and 2-3 mEq K+
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Quick, simple formula that estimates caloric
expenditure from weight alone
Assumes that for each 100 calories metabolized,
100 ml H2O will be required (50 ml/100 calories
for insensible loss, 67 ml/100 calories for urine
and 17 ml/100 calories gained from metabolism)
Not suitable for neonates < 14 days old
Holliday-Segar Method
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Holliday-Segar cont.
WEIGHT (kg) FLUIDS0 - 10 100 ml/kg/day
1120 1000 ml + 50 ml/kg for each kg above 10>20 1500 ml + 20 ml/kg for each kg above 20
Electrolyte needs per 100 ml: Na+3 mEqCl- 2 mEqK+2 mEq
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Body Surface Area Method
For non-dehydrated patients
Water 1500 ml/M2/24 hr
Sodium 30-50 mEq/M2/24 hr
Potassium 20-40 mEq/M2/24 hr
Mild dehydration
Water 2000 ml/ M2/24 hr
Moderate dehydration
Water 2500 ml/ M2/24 hr
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A 6 kg child needs 600 ml/day, which equals 25 ml/hr
A 35 kg child needs 1800 ml/day,which equals 75 ml/hr
A 14 kg child needs 1200 ml fluids with:
Na 36 mEq (3 mEq/100 cal)K 24 mEq (2 mEq/100 cal)
Cl 48 mEq (4 mEq/100 cal)
Examples
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Modifications
Increase Decrease
Fever (12% for each oC Renal failure
above 37 oC ) Heart failure
High ambient temperature Inappropriate secretion
Diabetes mellitus of ADH
Diabetes insipidus High-humidity respiratory
Vigorous exercise therapy
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Acute Renal Failure
Meticulous management of fluids and
electrolytes is required, including twice daily
weights, strict I/Os and close laboratory
monitoring
Oligo-anuric patients should receive fluid intake
equal to their total output; output must include
insensible lossesInsensible losses should be replaced with D5W
(or D10W)
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Neonates
Insensible losses in neonates vary with
gestational age and birth weight and may be
dramatically increased by phototherapy orradiant warmers
Newborns cannot concentrate urine as well
and GFR is lower so they are more prone tofluid overload
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Deficit Therapy
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Clinical Observations
Examination 3-5% (mild) 10% (moderate) >10% (severe)
Skin turgor Normal Tenting None
Skin-touch Normal Dry Clammy
Buccal mucosa/lips Moist Dry Parched
Eyes Normal Deep set Sunken
Crying/tears Present Reduced None
Fontanelle Flat Soft Sunken
CNS Consolable Irritable Lethargic
Pulse Regular Slight increase Increased
Urine output Normal Decreased Anuric
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Tenting
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ICF (mEq/L) ECF (mEq/L)
Sodium 20 135-145
Potassium 150 3-5Chloride --- 98-110
Bicarbonate 10 20-25
Phosphate 110-115 5
Protein 75 10
ECF and ICF Composition
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Na K Cl HCO3
Gastric juice 20-80 15 125 0Small-intestinal juice 100-140 15 155 40
Diarrhea 10-90 40 40 40
Sweat normal 10-30 10 25 0
Sweat CF 50-130 15 75 0
Electrolytes in Body Fluids (mEq/L)
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ECF and ICF Percentage of Loss
% fluid of deficit % fluid of deficit
Duration of illness from ECF from ICF3days 60 40
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Laboratory Tests that can Help
Urine specific gravity
Urine electrolytes
Fractional excretion of Na+ (UNa/PNa)/(UCr/PCr)
Serum electrolytes
Serum osmolality
2(Na) + BUN/2.8 + glucose/18
Renal function
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Isonatremic Dehydration
Patient is dehydrated and Na+is 135-145 mEq/L
Determine fluid deficit as percentage of weight based on
clinical findingsDetermine which parts of deficit come from ICF versus
ECF compartments based on duration of illness
ECF Na+loss = Fluid deficit (L) X % from ECF X 145
ICF K+ loss = Fluid deficit (L) X % from ICF X 150
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Hyponatremic Dehydration
Na+is < 135 mEq/L
Follow same steps as for isonatremic dehydration
Additional Na+ requirement =
(CDCP) X fD x wt
-CD is concentration desired
-CP is concentration present
-fD is distrubution factor as fraction of body weight (L/kg);
0.6-0.7 for Na+
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Hyponatremic Dehydration cont.
Frequently seen in children with vomiting and
diarrhea who have received tap water as an oral
replacementShock is an early symptom
Physical exam findings usually exaggerate amount
of dehydration
Correcting Na+to quickly in adults can lead to
central pontine myelinosis; this has not been
described in children
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Hypernatremic Dehydration
Before you start any fluid and electrolyte calculations you
need to determine free water (FW) amount
(Na+)actual(Na+)desired
(Na+) actual
Based on above formula for Na+< 170 mEq/L
approximately 4 ml of FW needed to bring Na+down by 1
mEq/L/kg; for Na+
> 170 mEq/L approximately 3 ml of FWneeded to bring Na+down by 1 mEq/L/kg
Subtract FW from total fluid deficit and replace remainder
in same way as done for isonatremic dehydration
x 100 ml/L x 0.6L/kg of body weight = ml/kg FW
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Hypernatremic Dehydration cont.
Mortality can be high
Often iatrogenic
The circulating volume is preserved at the expense of the
intracellular volume and circulatory disturbance is delayedThe patient looks better than you would expect based on
fluid loss
Always assume total fluid deficit of at least 10%
You only want to correct half of the fee water deficit infirst 24 hours if Na+< 175 mEq/L
For Na+> 175 mEq/L you do not want to correct faster
than 1 mEq/L/hr because of risk of cerebral edema
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Na (mEq/L) K (mEq/L)
Apple juice 0.4 26
Coke 4.3 0.1Gatorade 21 2.5
Milk 22 36
OJ 0.2 49
Pedialyte 45 20WHO ORS 90 20
Electrolytes in Popular Drinks
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Fluid cal/L Na K CL HCO3
mEq/l
D5W 170D10W 340
NS 154 154
1/2 NS 77 77
D5 1/4 NS 170 34 34LR 130 4 109 28
Alb. 25% 1000 100-160
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Clinical Dehydration Scenarios
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A 2 year old has a 4-day history of gastroenteritis, poor
fluid intake and infrequent urination. On exam you
find dryness of the mucous membranes, sunken eyes
with mild tenting of the skin. The serum sodiumis 137 mEq/L.
The weight is 10 kg.
You determine the child is suffering from about 10%
dehydration.
What are the fluid and electrolyte requirements?
Isonatremic Dehydration
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H2O Na K Cl
(ml) (mEq) (mEq) (mEq)
MaintenanceTotal deficit = 1000 ml
Extracellular fluid deficit
(60% of total)
Intracellular fluid deficit(40% of total)
Total
1000 30 20 40
600 87 - 60
400 - 60 -
2000 117 80 100
Isonatremic Dehydration
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You see a 3 year old who has had diarrhea and been
vomiting for 3 days. She has been drinking tap water
most of this time. Examination shows sunken eyes and
marked tenting of the skin but the child is not in shock.The serum Na+is 120 mEq/L.
The weight 14 kg.
You estimate the deficit as 7%.
What are the fluid and electrolyte requirements for this
patient?
Hyponatremic Dehydration
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H2O Na K Cl
(ml) (mEq) (mEq) (mEq)
Maintenance
Deficit (7% of 14 kg)
Extracellular fluid (60%)
Intracellular fluid (40%)
Additional sodium
{(135-120) x 0.6 x 14}Additional chloride
{(135-120) x 0.4 x 14}
Total
1200 36 24 48
600 87 - 60
400 - 60 -
- 126 - -
- - - 84
2200 249 84 192
Hyponatremic Dehydration
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You see a 6 month old suffering for 4 days from
severe diarrhea.
The mucous membranes are dry, skin feels doughy
and the child is somnolent and lethargic.
The serum Na+is 165 mEq/L.
The child weighs 5 kg and you assume the fluid deficit
is at least 10%.
What are the fluid and electrolyte requirements?
Hypernatremic Dehydration
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H2O Na K Cl
(ml) (mEq) (mEq) (mEq)
Maintenance
Total deficit = 500 mlFree water deficit
{(165-145)x1/2x4x5}
Remainder of deficit
(500-200) = 300 mlExtracellular (60%)
Intracellular (40%)
Total
500 15 10 20
200 - - -
180 26 - 18120 - 18 -
1000 42 29 38
Hypernatremic Dehydration
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Phase Approach
PHASE 1
Emergency restoration of circulation if patient ishypovolemic
10-20 ml/kg of isotonic fluids only PHASE 2
Replacement of of the fluid loss (deficit andmaintenance) in first 8 hours
PHASE 3 Replacement of remaining of the fluid loss
(maintenance and remaining deficit) in next 16 hours
Replacement of potassium after voids
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Nursing Orders
Write the type of basic fluid
D51/2 NS most commonly used on pediatric wards(premixed bags are present)
Can create any fluid you desire but may take longer to getif not premixed available
Add other electrolytes as desired to the basic fluid
Most commonly KCL added at 20 mEq/L but may needmore to replace deficit
Often only added after first void in dehydrated patients
Write how fast you want it to run in ml/hr
For example for 15 kg non-dehydrated child writeD51/2NS + 20 mEq/L of KCL to run at 50 ml/hr
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Patient Rounds
Report total 24 hr intake
Report what part of total intake was oral v.s.intravenous v.s. G-tube
Subsequently report intake as ml/kg/day forchildren with weight < 10 kg
Intake for children with weight > 10 kg should bereported as % of maintenance
For example a 25 kg afebrile child had a totalintake of 2000 ml for the past 24 hr, 1600 ml wasfrom iv fluids and 400 ml was po, this represents125 % of maintenance need for this child
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Patient Rounds cont.
Report total 24 hr output
Report where this output came from (urine,
vomit, diarrhea, chest tube, stoma etc)
For the urinary output report this in
ml/kg/hr as well