fen basics

7/27/2019 Fen Basics

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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?



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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



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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?



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H2O Na K Cl


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



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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?



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H2O Na K Cl


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



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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

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