Fluids and Electrolytes
David A. Listman, MD
St. Barnabas Hospital
Pediatric Emergency Medicine
Goals and Objectives


Understand where fluid and salts are in body
Understand and be able to order
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maintenance fluids
Deficit fluids
Be familiar with causes and treatment of hypo/
hyper- natremia
Provide fluids to patients in special
circumstances
Body Fluid Composition

Total body water (TBW)


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Intracellular fluid

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75-80% of body weight at birth
60% of body weight after 1 year
2/3 of TBW or about 40% body weight
Extracellular fluid

1/3 of TBW or about 20% body weight
¾ Interstitial fluid
 ¼ Plasma

Need for Fluid Therapy



Maintenance of fluids in patients with
insufficient intake (i.e.. NPO)
Replacement of already diminished fluid
volume (i.e.. dehydration, trauma)
Replace ongoing losses (i.e.. GI, renal)
Maintenance Fluids



Replacement of insensible losses due to
heat dissipation
Replacement of Urinary Losses
Maintenance water needs are related to
caloric requirement
Maintenance Fluids

Caloric requirement

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100 kcal/kg/24hr up to 10 kg
1000 kcal +
50 kcal/kg/24hr
per kg over 10 up to 20
1500 kcal +
20 kcal/kg/24 hr per kg over 20
Maintenance Fluids

Fluid requirement

40 ml/100 kcal/ 24 hr to replace insensible losses
60 ml/100 kcal/ 24 hr to replace urine losses

100 ml/ 100 kcal/ 24 hours total


SO:
Maintenance Fluids

Caloric requirement

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100 kcal/kg/24hr up to 10 kg
1000 kcal +
50 kcal/kg/24hr
per kg over 10 up to 20
1500 kcal +
20 kcal/kg/24 hr per kg over 20
Maintenance Fluids

Fluid requirement


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100 ml/kg/24hr
up to 10 kg
1000 ml +
50 ml/kg/24hr
per kg over 10 up to 20
1500 ml +
20 ml/kg/24 hr
per kg over 20
Maintenance Fluids

Fluid requirement


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100/ 50/ 20
Divided by 24 hours (or 25)
4 / 2/ 1 (cc’s per hour)
Maintenance Fluids

Few examples:

8 kg
8 x 100 = 800 cc’s/ day
 800 / 24 = 33.3 cc’s/ hr

or

8 x 4 = 32 cc’s/ hr
Maintenance Fluids

Few examples:

18 kg
10 x 100 = 1000
8 x 50 = 400
 1000 + 400 = 1,400 cc’s/ day
 1,400 / 24 = 58.3 cc’s/ hr

or
10 x 4 = 40
 40 + 16 = 56 cc’s/ hr

8 x 2 = 16
Maintenance Fluids

Few examples:

28 kg

10 x 100 = 1000
10 x 50 = 500 8 x 20 = 160
1000 + 500 + 160 = 1,660 cc’s/ day
 1,660 / 24 = 69.2 cc’s/ hr


or
10 x 4 = 40

40 + 20 + 8 = 68 cc’s/ hr
10 x 2 = 20
8x1=8
Maintenance fluids


We’ve got the water, do we need anything
else?
Is it necessary to replace electrolytes?


Recent data shows significant risk of
hyponatremia in hospitalized patients
Hyponatremia can lead to fluid shift into cells
causing cellular (and cerebral) edema
Maintenance fluids
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Daily sodium requirement
2-4 meq / kg / day

Daily Potassium requirement
1-2 meq / kg / day
This is a flat need per kilo and does not
decrease as water needs do
Maintenance fluids- sodium
This is a flat need per kilo and does not
decrease as water needs do
So
As volume required goes down, sodium
needed per liter goes up
Maintenance fluids- sodium
Some examples-
10 kg child needs 20-40 meq Na+ per day
10 kg child needs 1000 cc’s per day
20-40 meq/ liter
20 kg child needs 40-80 meq Na+ per day
20 kg child needs 1500 cc’s per day
26-53 meq/ liter
50 kg child needs 100-200 meq Na+ per day
50 kg child needs 1800 cc’s per day
55-110 meq/liter
Sodium concentrations

Normal saline (0.9% NaCl/L)
154 mEq Na+/L

1/2 normal saline (0.45% NaCl/L)
77 mEq Na+/L

1/3 normal saline (0.33% NaCl/L)
57 mEq Na+/L
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1/4normal saline (0.2% NaCl/L)
34 mEq Na+/L
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Ringer’s lactate
130 mEq Na+/L
(Contains 4 mEq K+, 109 mEq Cl-, 28 mEq bicarb
equivalent all/Liter, and 3 mg/dl of Ca++)
What else goes in it?

Dextrose

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5% dextrose is insufficient to nourish a
patient
To spare catabolism of glycogen and protein
What else goes in it?

Potassium
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Daily requirement 1-2 meq/kg/day
Need for Fluid Therapy



Maintenance of fluids in patients with
insufficient intake (i.e.. NPO)
Replacement of already diminished fluid
volume or deficit (i.e.. dehydration,
trauma)
Replace ongoing losses (i.e.. GI, renal)
Treatment of volume loss
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Decrease in extracellular fluid
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Initial treatment- rapid expansion of ECF
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Bolus of isotonic fluid (i.e.. NS or LR)
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Should not include dextrose
Repeat bolus as necessary to improve perfusion
Replacement of deficit
Continue maintenance
Frequent reevaluation of

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Vital sign
Electrolytes
Urine output and urine specific gravity
Treatment of volume loss

Decrease in extracellular fluid
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Initial treatment- rapid expansion of ECF
Bolus of isotonic fluid (i.e.. NS or LR)
 Repeat bolus as necessary to improve perfusion
 Replacement of deficit
 Continue maintenance
 Frequent reevaluation of
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Vital sign
Electrolytes
Urine output and urine specific gravity
Estimate of Fluid Deficit

Subtract
pre-illness weight - current weight

Calculate using current weight and %
dehydration
Pre-illness wt (kg)
=
Current wt (kg)

100
100 - % estimated dehydration
Current Weight x % dehydration

(slightly underestimates)
Estimate of Dehydration
Skin Turgor
↓,Tenting
Oral Mucosa
Tears
Fontanelle
Heart Rate
Blood Pressure
Urine OP
CNS/ LOC
Pulse Quality
Skin
Mild
Moderate
Severe
Sl Dry
Sl ↓
Normal/ Flat
Normal/ Sl ↑
Normal
Mild Oliguria
Very Dry
Absent
Depressed
↑
Normal/ Sl ↓
Oliguria
Irritable/Listless
Rapid
Cool/ Pale
Parched
Absent
Sunken
Normal/Elastic ↓
Alert/ Responsive
Full
Warm/ Pink
Very
Marked Tachycardia
↓
Oliguria/ Anuria
Minimal/Nonresponsive
Rapid/ weak
Cool
Estimate of Dehydration
Mild
Moderate
Severe
<1yr 5%
10%
15%
Older 3%
6%
9%
Replacement of Deficit
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Deficit volume
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Replace ½ over 1st 8 hours
Replace ½ over next 16 hours
Don’t forget maintenance fluid
Replacement of Deficit
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Example
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16 kg child 10% dehydrated
Bolus(es) normal saline 20 ml/kg rapidly
Maintenance 1,000 + 300= 1,300 / 24 = 54cc/hr
Deficit 1,600 ml
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800 over 1st 8 hours=100ml /hr
800 over next 16 hours = 50ml /hr
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Total 154 ml /hr x 8 hours then 104 ml/hr x16 hours
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Not well approximated by 1 ½ maintenance
Need for Fluid Therapy


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Maintenance of fluids in patients with
insufficient intake (i.e.. NPO)
Replacement of already diminished fluid
volume or deficit (i.e.. dehydration,
trauma)
Replace ongoing losses (i.e.. GI, renal)
Ongoing losses
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Continued loss in excess of normal
maintenance
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GI loss- vomit/ diarrhea
Surgical drains/ NG tube
Increased insensible losses- fever
Increased urine output
Ongoing losses
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Continued loss in excess of normal
maintenance
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Volume can often be measured
NG output
 Stool
 Urine
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Type of fluid needed for replacement
Can be measured
 Can be estimated
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Oral Rehydration
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Better than IV if tolerated
What makes a good oral rehydration fluid?
Proper balance of Na+ and glucose
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Na+/glucose co-transporter in intestine non
ATP dependant
Water follows passively
Oral Rehydration
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What makes a good oral rehydration fluid?
Proper balance of Na+ and glucose

Na+/glucose co-transporter in intestine non ATP
dependant
1 : 1 osmolar ratio
Na+ 90 meq/l, glucose 111meq/l (2% solution)

Some K+ to prevent Hypokalemia
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Oral Rehydration
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What makes a good oral rehydration fluid?
MMWR November 21, 2003 / 52(RR16);1-16
Oral Rehydration
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Mild to moderate dehydration
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Deficit 50-100 ml of ORS/kg body weight
during 2-4 hours
Maintenance100 ml ORS/kg per day
limited volumes of fluid (e.g., 5 mL or 1
teaspoon) should be offered at first, with the
amount gradually increased as tolerated.
Hypo/ Hypernatremia

More to do with water than salt status
(usually)

Hyponatremia
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free water excess
Hypernatremia

Free water deficit
Hyponatremia
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Serum Na+ < 135
Common in hospitalized children
Kidneys unable to dilute urine and excrete
free water
Hyponatremia

Measure serum Osm to confirm low serum
Osm before aggressive treatment

Normal or high serum Osm with
pseudohyponatremia
Hyperglycemia
 Hyperlipidemia
 Hyperproteinemia
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Hyponatremia
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True hyponatremia causes influx of water
into cells
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Cellular swelling
Cerebral edema
Exacerbated by hypoxia
Hyponatremia
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Symptoms
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Headache, nausea, vomit, behavioral changes
Seizures, resp arrest, dilated pupils, decorticate
posturing
Hyponatremia
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Causes of SIADH
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CNS
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Pulmonary
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Meningitis
CNS neoplasm
Hydrocephalus
Pneumonia
Asthma
TB
Positive Pressure Ventilation
Pneumothorax
Drugs
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Vincristine, cyclophosphamide
Carbamazepine
Hyponatremia
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Post-operative
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Multi-factorial
Volume depletion
 Stress
 ADH
 Hypotonic fluids
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Hyponatremia
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Water intoxication
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Newborns
Fed dilute formula or water supplement
 Decreased ability to maximally concentrate urine
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Hyponatremia- treatment
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If neurologic signs/ seizure
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Hypertonic 3% saline (514 meq/l)
1 ml/kg/hr should raise Na+ by 1 meq/l
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Goals
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Raise Na+ by 1 meq/hr until

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Symptoms resolve
Serum Na+ has risen 20-25 meq/l
Serum Na+ 125-130 meq/l
or
or
Hyponatremia- treatment

Asymptomatic

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Restrict free water intake
Avoid hypotonic fluids
Hyponatremia

Recent evidence suggests use of isotonic
rather than hypotonic fluids in post-op,
gastroenteritis prevents hyponatremia.
Hypernatremia
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Serum Na+ >145 meq/l
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Debilitated patients
Neurologically impaired patients
Ineffective breastfeeding
Inability to access sufficient free water
Inability to maximally concentrate urine
Hypernatremia
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Clinical manifestations
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Water moves from intracellular to extracellular space
Maintenance of ECF volume so classic signs of volume
depletion are absent
Agitation, irritability, coma
Hypernatremia
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Clinical manifestations
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Water moves from intracellular to extracellular space
Cell shrinkage
Brain cell volume decreases
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If acute and rapid can lead to
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Intracranial hemorrhage
Venous sinus thrombosis
Over short time brain cells increase intracellular
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Na+, K+, amino acids, unmeasured organic substances
Not easily decreased so rapid rehydration will cause cerebral
edema
Hypernatremia
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Treatment

Correct serum Na+ and water deficit
Free water deficit =
4ml x lean body weight (kg) x (serum Na+ – desired Na+ )
Add maintenance fluid and correct slowly

At least 48-72 hours if serum Na+ > 170
Various Causes of Volume Loss

Trauma- when is it time for blood

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20 ml’s/kg NS or LR x 2
Then whole blood or PRBC’s
Diabetes

IDDM what is the cause and presentation
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Not enough insulin produced
Break down of fats and protein in response to low
insulin levels
How does it present?
What are the fluid and electrolyte abnormalities?
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Glucose
Sodium
Potassium
Phos
pH
Diabetes
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Very hyperosmolar
Pseudohyponatremia
Initial Boluses to restore intravascular volume
Slow deficit replacement to prevent cerebral
edema
Constant infusion of insulin regardless of blood
glucose
Add IV glucose if necessary
Diabetes
•
Usual fluids
–
–
Initial bolus(es) of Normal Saline
After 1st hour
•
•
•
Insulin infusion usually 0.1 units / kg/ hour
½ NS with 20KCL and 20 K Phos at maintenance plus slow
deficit replacemement
Once sugar falls
–
2 bags
•
•
•
•
½ NS with 20KCL and 20 K Phos
D10 ½ NS with 20KCL and 20 K Phos
Total of these 2 infusions to equal maintenance plus slow
deficit replacement
Can titrate to provide anywhere from no dextrose to D10
without changing electrolytes depending on the CBG’s
Burns


Tremendous fluid losses
Parkland formula
4 ml/ kg/ % BSA burns (2nd and 3rd degree)/ 24 hours
half over first 8 hours ½ over next 16 hours
in addition to maintenance
Summary

Provide water, sodium, glucose and
potassium to patients who have a variety
of disturbances of fluid and sodium
balance