Dehydration
Paul R. Earl
| Biológicas
Facultad de Ciencias
Universidad Autónoma de Nuevo
León
San Nicolás, N. L., Mexico
pearl@dsi.uanl.mx
 Dehydration or volume depletion is classified as
mild, moderate or severe based on how much body
fluid is lost. When severe, dehydration is a lifethreatening emergency. Volume depletion denotes
lessening of the total intravascular plasma, whereas
dehydration denotes loss of plasma-free water
disproportionate to the loss of sodium. Potassium and
other electrolytes including buffers líke phosphates
need to be considered. Children, especially those
younger than 4 years old, are more susceptible to
volume depletion as a result of vomiting, diarrhea or
increases in insensible water losses.
 Dehydration can be caused by losing too much fluid, not
drinking enough water or fluids, or both. Vomiting and
diarrhea are common causes.
 Dehydration is classified as mild, moderate or severe
based on how much body's fluid is lost. Symtons include:
 Dry or sticky mouth.
 Dizziness.
 Low or no urine output; concentrated urine is dark yellow.
 Not producing tears.
 Sunken eyes.
 Markedly sunken fontanelles (the soft spot on the top of the
head in a baby).
 Lethargic or comatose.
 In addition to the symptoms of actual dehydration, you may
also have:
– vomiting and
– diarrhea.
 Drinking fluids is usually sufficient for mild dehydration. It is
better to have frequent, small amounts of fluid (using a
teaspoon or syringe for an infant or child) rather than trying
to force large amounts of fluid at one time. Drinking too
much fluid at once can bring on more vomiting.
 Electrolyte solutions or freezer pops are especially
effective. These are available at pharmacies. Sport drinks
contain a lot of sugar and can cause or worsen diarrhea. In
infants and children, avoid using water as the primary
replacement fluid.
Intravenous fluids and hospitalization may be necessary for
moderate to severe dehydration. The doctor will try to identify
and then treat the cause of the dehydration.
 Treatment includes starting NS@20ml/kg slow push until
signs of severe dehydration disappear. Avoid Ringer Lactate
till patient passes urine. Maintainence fluid depends on body
weight. Either DNS or RL may be used 10kg and less
100ml/Kg 10-20 Kg 1000mL+50ml/kg 20+ Kg 1500ml+ 20
ml/kg It may be advisable to give half the calculated fluid in
the first 8 hours and the remaining over the next 16 hours
 Precautions
 check for pulmonary oedema replenish Potassium as
required Chills may occur due to fluid administration rule out
infectious causes
 Most cases of stomach viruses (also called viral gastroenteritis)
tend to resolve on their own after a few days.
 Boxers under hot lights sip water, then usually spit it out. They
don`t seem to know that that water could save them from a
coma during heat prostration!
 Pathophysiology
 Pediatric dehydration is frequently the result of gastroenteritis,
characterized by vomiting and diarrhea. However, other causes
of dehydration may include poor oral intake due to diseases
such as stomatitis, insensible losses due to fever, or osmotic
diuresis from uncontrolled diabetes mellitus.
 Pathophysiology
 Pediatric dehydration is frequently the result of gastroenteritis,
characterized by vomiting and diarrhea. However, other causes
of dehydration may include poor oral intake due to diseases
such as stomatitis, insensible losses due to fever, or osmotic
diuresis from uncontrolled diabetes mellitus.
 Volume depletion denotes lessening of the total intravascular
plasma, whereas dehydration denotes loss of plasma-free water
disproportionate to the loss of sodium. The distinction is
important because volume depletion can exist with or without
dehydration, and dehydration can exist with or without volume
depletion
 In children with dehydration, the most common underlying
problem actually is volume depletion, not dehydration.
Intravascular sodium levels are within the reference range,
indicating that excess free water is not being lost from
plasma. Rather, the entire plasma pool is contracted with
solutes (mostly sodium) and solvents (mostly water) lost in
proportionate quantities. This is volume depletion without
dehydration. The most common cause is excessive
extrinsic loss of fluids.
 Pediatric patients, especially those younger than 4 years,
tend to be more susceptible to volume depletion as a
result of vomiting, diarrhea, or increases in insensible
water losses. Significant fluid losses may occur rapidly.
The turnover of fluids and solute in infants and young
children can be as much as 3 times that of adults. This is
because of the following:
 Higher metabolic rates
 Increased body surface area to mass index
 Higher body water contents (Water comprises
approximately 70% of body weight in infants, 65% in
children, and 60% in adults.)
Sodium considerations
 Volume depletion can be concurrent
with hyponatremia. This is characterized by plasma
volume contraction with free water excess. An
example is a child with diarrhea who has been given
tap water to replete diarrheal losses. Free water is
replenished, but sodium and other solutes are not.
 In hyponatremic volume depletion, the person may appear
more ill clinically than fluid losses indicate. The degree of
volume depletion may be clinically overestimated. Serum
sodium levels less than 120 mEq/L may result in seizures.
If intravascular free water excess is not corrected during
volume replenishment, the shift of free water to the
intracellular fluid compartment may cause cerebral edema.
With true dehydration, plasma volume contracts with
disproportionate further free water loss. An example is the
child with diarrhea whose fluid losses have been
replenished with hypertonic soup, boiled milk, baking soda,
or improperly diluted infant formula. Volume has been
restored, but free water has not.
 In hypernatremic volume depletion, the patient may appear
less ill clinically than fluid losses indicate. The degree of
volume depletion may be underestimated. Usually, at least
a 10% volume deficit exists with hypernatremic volume
depletion.
As in hyponatremia, hypernatremic volume depletion may
result in serious central nervous system (CNS) effects as a
result of structural changes in central neurons. However,
cerebral shrinkage occurs instead of cerebral edema. This
may result in intracerebral hemorrhage, seizures, coma,
and death. For this reason, volume restoration must be
performed gradually over 24 hours or more. Gradual
restoration prevents a rapid shift of fluid across the bloodbrain barrier and into the intracellular fluid compartment.
Potassium considerations
 Potassium shifts between intracellular and extracellular
fluid compartments occur more slowly than free water
shifts. Serum potassium level may not reflect intracellular
potassium levels. Although a potassium deficit is present in
all patients with volume depletion, it is not usually clinically
significant. However, failure to correct for a potassium
deficit during volume repletion may result in clinically
significant hypokalemia. Potassium should not be added to
replacement fluids until adequate urine output is obtained.
Acid and base problems
 Clinicians may observe derangements of acid-base
balance with volume depletion. Some degree of metabolic
acidosis is common, especially in infants.
Mechanisms include bicarbonate loss in stool and ketone
production. Hypovolemia causes decreased tissue
perfusion and increased lactic acid production. Decreased
renal perfusion causes decreased glomerular filtration rate,
which, in turn, leads to decreased hydrogen (H+) ion
excretion. These factors combine to produce a metabolic
acidosis.
 In most patients, acidosis is mild and easily corrected with volume
restoration (as increased renal perfusion permits excretion of excess
H+ ions in the urine). Administration of glucose-containing fluids
further decreases ketone production.
Frequency
United States
Pediatric dehydration, particularly that due to gastroenteritis, is a
common ED complaint. Approximately 200,000 hospitalizations
and 300 deaths per year are attributed to gastroenteritis each
year.
International
According to the Centers for Disease Control and
Prevention (CDC), for children younger than 5 years,
the annual incidence of diarrheal illness is
approximately 1.5 billion, while deaths are estimated
between 1.5 and 2.5 million. Though these numbers are
staggering, they actually represent an improvement
from the early 1980s, when the death rate was
approximately 5 million per year.
Mortality/Morbidity
 Morbidity varies with the degree of volume depletion and
the underlying cause.
 The severely volume-depleted infant or child is at risk for
death from cardiovascular collapse.
 Hyponatremia resulting from replacement of free water
alone may cause seizures.
 Improper management of volume repletion may cause
iatrogenic morbidity or mortality.
Age
 Infants and younger children are more susceptible to
volume depletion than older children.
Clinical History
The goal of the history and physical examination is to
determine the severity of the child's condition. Classifying the
degree of dehydration as mild, moderate, or severe
accurately allows for appropriate therapy and disposition of
the patient in a timely fashion.
Obtaining a complete history from the parent or caregiver is
important because it provides clues to the type of
dehydration present.
The emergency physician should be diligent in obtaining the
following information:
 Feeding pattern and fluids given
 Number of wet diapers compared with normal
 Fluid loss (eg, vomiting, oliguria or anuria, diarrhea)
 Possible ingestions
 Activity
 Medications
 Heat and sunlight exposures
Physical

The following table highlights the physical findings seen with different levels of
pediatric dehydration.
Symptom
Mild (<3% body
weight lost)
Moderate (3-9% body
weight lost)
Severe (>9% body
weight lost)
Mental
status
Normal, alert
Restless or fatigued,
irritable
Apathetic, lethargic,
unconscious
Heart rate
Normal
Normal to increased
Tachycardia or
bradycardia
Quality of
pulse
Normal
Normal to decreased
Weak, thready,
impalpable
Breathing
Normal
Normal to increased
Tachypnea and
hyperpnea
Eyes
Normal
Slightly sunken
Deeply sunken
Fontanelle
Normal
s
Slightly sunken
Deeply sunken
Tears
Normal to decreased
Absent
Normal
Mucous
membranes
Moist
Dry
Parched
Skin turgor
Instant recoil
Recoil <2 seconds
Recoil >2 seconds
Capillary
refill
<2 seconds
Prolonged
Minimal
Extremities
Warm
Cool
Mottled, cyanotic
Symptom
Mild (<3% body
weight lost)
Moderate (3-9% body
weight lost)
Severe (>9% body
weight lost)
Mental
status
Normal, alert
Restless or fatigued,
irritable
Apathetic, lethargic,
unconscious
Heart rate
Normal
Normal to increased
Tachycardia or
bradycardia
Quality of pulse
Normal
Normal to
decreased
Weak, thready,
impalpable
Breathing
Normal
Normal to increased
Tachypnea and
hyperpnea
Eyes
Normal
Slightly sunken
Deeply sunken
Fontanelles
Normal
Slightly sunken
Deeply sunken
Tears
Normal
Normal to
decreased
Absent
Mucous
membranes
Moist
Dry
Parched
Skin turgor
Instant
recoil
Recoil <2 seconds
Recoil >2 seconds
Capillary refill
<2 seconds
Prolonged
Minimal
Extremities
Warm
Cool
Mottled, cyanotic
 Of these, the most accurate in identifying the level of
dehydration are capillary refill, skin turgor, and breathing.
The least accurate are mental status, heart rate and
fontanelle appearance.
Causes
 In most cases, volume depletion in children is from fluid losses
from vomiting or diarrhea.
 Vomiting may be caused by any of the following systems or
processes:
 CNS (eg, infections, space-occupying lesions)
 GI (eg, gastroenteritis, obstruction, hepatitis, liver failure,
appendicitis, peritonitis, intussusception, volvulus, pyloric
stenosis, toxicity [ingestion, overdose, drug effects])
 Endocrine (eg, diabetic ketoacidosis [DKA], congenital adrenal
hypoplasia, Addisonian crisis)
 Renal (eg, infection, pyelonephritis, renal failure, renal tubular
acidosis)
 Psychiatric (eg, psychogenic vomiting) - This is not seen in
infants and is rare in children compared with adults.
Diarrhea may be caused by any of the following
systems or processes:
 GI (e.g., gastroenteritis, malabsorption, intussusception,
irritable bowel, inflammatory bowel disease, short gut
syndrome)
 Endocrine (eg, thyrotoxicosis, congenital adrenal
hypoplasia, Addisonian crisis, diabetic enteropathy)
 Psychiatric (eg, anxiety)
 Volume depletion not caused by vomiting or diarrhea may
be divided into renal or extrarenal causes.
– Renal causes include use of diuretics, renal tubular
acidosis, and renal failure (eg, trauma, obstruction, saltwasting nephritis). The effects of diabetes insipidus,
hypothyroidism, and adrenal insufficiency also fall into
this category.
– Extrarenal causes include third-space extravasation of
intravascular fluid (eg, pancreatitis, peritonitis, sepsis,
heart failure); insensible losses from fever, sweating,
burns, or pulmonary processes; poor oral intake; and
hemorrhage.