Transcript PEDIATRICS

Dr Masood EntezariAsl
INTRODUCTION
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the incidence of anesthesia-related mortality and
morbidity remains higher in infants than in adults
and higher in younger than older children.
In the post anesthesia care unit(PACU), problems
primarily or secondarily related to airway
complications are more likely to develop in the
youngest infants.
The incidence of critical events (most often
respiratory) is higher in infants younger than 1 year
than in children older than 1 year, especially in
infants weighing less than 2 kg
the frequency of anesthetic cardiac arrest in infants
is less when care is delivered by pediatrictrained/experienced practitioners
FLUIDS AND ELECTROLYTES
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Considerations that influence fluid homeostasis
include:
(1) anatomic factors related to the distribution
of body fluids
(2) physiologic factors such as basal
requirements and abnormal metabolic rate
(3) functional immaturity of the kidneys and liver
(4) pathologic factors secondary to the special
setting of illness, anesthesia, and surgery
Maintenance Requirements
Weight (kg)
Hourly Fluid Requirements 24-hr Fluid Requirements
<10
4 m L/kg
100 mL/kg
11-20
40 mL + 2 mL/kg >10 kg
1000 mL + 50 mL/kg >10 kg
20>
60 mL + 1 mL/kg >20 kg
1500 mL + 20 mL/kg >20 kg
Replacement of Ongoing Losses
Type of Surgery
Specific Example
Hourly Fluid
Noninvasive
Inguinal hernia repair,
clubfoot repair
0-2 mL/kg/hr
Mildly invasive
Ureteral reimplantation
2-4 mL/kg/hr
Moderately invasive
Elective bowel reanastomosis
4-8 mL/kg/hr
Significantly invasive
Bowel resection for necrotizing ≥10 mL/kg/hr
enterocolitis
Clinically Important Formulas for Perioperative Management of Children
Volume of Packed Red Blood Cells (PRBCs)
PRBCs(mL) = EBV x DesiredHctx (Actual Hct/Hct of PRBCs)
EBV,estimated blood volume; Hct, hematocrit
Intraoperative Fluid Administration (Consider Four Factors)
1. "Catch up" (maintenance rate x hours NPO)
2. Maintenance fluid
3. Ongoing losses (blood loss, third spacing)
4. Special considerations (calcium, glucose, coagulation factors)
Intraoperative Glucose
Maintenance requirement of glucose for newborn (4 mg/kg/min = 240
mg/kg/hr)
Maintenance fluid (Ds = 50 mg glucose/mL)(4 mL/kg/min = 200 ml/kg/hr)
Delivery of a Dissolution at a rate greater than 4 mL/kg/hr may lead to
hyperglycemia; preoperative evaluation includes noting the blood glucose
concentration (Chemstrip/Dextrostix) level at a specific infusion (mg/kg/min) of
glucose
Normal Distribution of Water
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Total-body water consists of extracellular fluid (ECF)
and intracellular fluid (ICF)
ECF includes plasma volume and interstitial fluid
volume
In the early stages of fetal development, water
constitutes approximately 94% of body weight
As gestation continues, total-body water decreases
so that at 32 weeks' gestation, 80% of body weight
is water and, at term, total-body water is 78% of
body weight
Adult proportions of fluid to body weight are
reached between the age of 9 months and 2 years
Adult females have approximately 55% of their
body weight as total-body water, with males
averaging 60%
RELATIONSHIP OF BODY FLUID
COMPARTMENTS
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The relationship of ECF and ICF also changes
during fetal growth
ECF decreases from 60% of body weight at the
fifth month to approximately 45% at term
ICF increases from 25% in the fifth month of fetal
life to 33% at birth
In adult males, the ICF and ECF compartments
approximate 40% and 20% of body weight,
respectively
The plasma volume component of ECF remains
constant at about 5% of body weight throughout life
Interstitial water is greater in infants (40%) and
declines to 15% and 10% of body weight in men
and women, respectively
ELECTROLYTECOMPOSITION OF
BODY FLUIDS
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The electrolyte composition of the body fluids of
infants is also different from that in adults
Higher plasma chloride and lower bicarbonate
and pH imply a mild metabolic acidosis with
reduced buffering power (Tables)
In the first 10 days of postnatal life (term
infants), serum potassium levels may be as high
as 6.0 to 6.5 mEqlL
In term infants, serum potassium ranges from 3.5
to 5.5 mEqlL after the first 2 to 3 weeks of life
Another unique feature of newborns is the
reduced protein concentration, which results in
lower intravascular oncotic pressure
Laboratory Values in Children
Newborn
1 Week Old
1 Month Old
1 Year Old
Glucose (mg/dL)
40-60
50-80
60-100
60-100
Total CO2 (mEq/L)
13-22
15-22
20-28
22-28
Chloride (mEq/L)
98-113
98-113
98-107
98-107
Potassium (mEq/L)
3.9-5.9
4.1-5.5
3.4-4.7
3.4-4.7
Total calcium (mg/d L)
7.6-10.4
9.0-11.0
9.0-11.0
8.8-10.8
Ionized calcium
(mmol/L)
1.05-1.37
1.10-1.42
1.20-1.38
1.20-1.38
Total protein (g/d L)
4.4-7.6
4.4-7.6
3.6-7.4
3.7-7.5
Albumin (g/dL)
2.2-4.0
2.5-5.5
2.1-4.8
1.9-5.0
Developmental Changes in Blood Gas
Values in children
Age
pH
Pao₂
Paco₂
1 hour
7.26-7.29
60
55
24 hours
7.37
70
33-35
1 week
7.40
70-80
35
1-10 months
7.40
85-90
35
4-8 years
7.39-7.40
90-95
37
12-18 years
7.35-7.45
95-100
35-45
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Over the first week of life, water exchange is often
negative because of ongoing losses through the
skin, lungs, and urine in the setting of limited intake
A 7-kg infant with a 21OO-mL ECF volume takes in
and excretes approximately 700 to 1000 mL of fluid
daily, which represents a 33% turnover in ECF
By comparison, a 70-kg adult with a 14,000-mL
ECF volume excretes approximately 2000 mL of
fluid daily for a 14% turnover
This high rate of fluid exchange may expose infants
to more rapid development of both dehydration and
over hydration
PEDIATRIC AIRWAY
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Preoperatively, the anesthesiologist must meticulously
assess all aspects of the airway to develop detailed and
flexible
plans
for
(1)
intubating
the
trachea,
(2) intraoperative
airway management
(3) postoperative
recovery (Table(
The anesthetic plan for management of the child's airway
may be influenced by the site of surgery
Maintaining upper airway patency is an active process
that is depressed during general anesthesia
During spontaneous ventilation, the upper airway is
exposed to potentially collapsing negative pressure during
inspiration
The pharynx is prone to collapse because negative
pressure pulls the tongue against the pharynx
General anesthesia depresses activity of the upper airway
and thereby predisposes to oropharyngeal obstruction
Endotracheal Tube Sizes
Age
Size: ID (mm)
Depth (cm)
Preterm
2.5
6-8
Term
3.0
9-10
6 months
3.0-3.5
10
1-2 years
4.0
10-11
3-4 years
4.5
12-13
5-6 years
5.0
14-15
10 years
6.0
16-17
The contribution of the tongue to airway
obstruction is exaggerated in infants because
the tongue is large relative to the total volume
of the mouth
 Infants or children with small upper airways
secondary to craniofacial anomalies, weakness
as a result of neuromuscular or central nervous
system disorders, impingement on the airway
secondary to tumors or hemangiomas, or
dysfunction of the tracheobronchial tree
because of an upper respiratory infection (URI)
are especially prone to pharyngeal obstruction
by the tongue
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Head position is important in maintaining upper
airway patency during anesthesia
 Flexing an infant's head may cause the upper
airway to collapse more readily
 In addition, the small, soft airways of neonates
(especially premature neonates) are more
compressible if the neck is flexed
 Extending or keeping the neck in a neutral
position while applying positive airway pressure
during ventilation with a bag and facemask is
important, particularly during induction of
general anesthesia
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Unique Anatomic Features
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The larynx of infants is higher in the neck (C3-4)
than in adults (C4-5)
An infant's epiglottis is large, but it is narrow and
short
A straight laryngoscope blade may allow the larynx
of a normal infant to be visualized more easily
When laryngeal anatomy is distorted by
craniofacial anomalies (micrognathia or midface
hypoplasia), direct visualization of the larynx may
be impossible, and alternative methods of securing
the airway should be available
An infant's vocal cords are slanted such that the
posterior commissure is more cephalad than the
anterior commissure
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This arrangement may predispose the anterior
sublaryngeal airway to trauma from an endotracheal
tube
The subglottic area is prone to traumatic injury from
an endotracheal tube because the narrowest portion
of an infant's larynx is at the cricoid cartilage
In adults, the narrowest portion is the glottic rim
Thus, an endotracheal tube that easily passes
through the vocal cords of an infant or child may fit
snugly in the subglottis and cause subglottic edema
and symptoms of increased airway resistance after
tracheal extubation
This increased resistance is usually reversible, but
subglottic stenosis may develop after prolonged
tracheal intubation with an oversized endotracheal
tube
Airway Assessment
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Difficult tracheal intubation generally occurs when facial or
oral pathology prevents visualization of the larynx or when
the larynx is easily visualized by direct laryngoscopy but a
lesion in the supraglottic, glottic, or subglottic region
interferes with insertion of the endotracheal tube
When the past medical history documents previous difficult
airway management and tracheal intubation, it is
recommended that a physician experienced in performing
pediatric bronchoscopy be present during initial airway
management
Fiberoptic airway endoscopy with or without the aid of a
laryngeal mask airway (LMA) may be indicated for securing
a difficult airway
In some circumstances, it may be prudent to have
available a surgeon skilled in performing cricothyrotomy or
tracheostomy (or both)
In some situations, performing a controlled tracheostomy
may be less traumatic than persisting with multiple attempts
at direct laryngoscopy
DEVELOPMENTAL
PHYSIOLOGY
DEVELOPMENTAL PHYSIOLOGY
Respiratory System
 Circulatory System
 Renal Function
 Hematology
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Respiratory System (Table)
Lung Development
 Alveoli develop mainly after birth and
increase from 20 million terminal air sacs in
a newborn to approximately 300 million
alveoli at 18 months of age
 In general, extra uterine viability is first
likely after 26 weeks when the respiratory
saccules
have
developed
and
vascularization by capillaries has occurred
 Supportive care of a premature infant
commonly includes oxygen and positive
pressure ventilation, and infections are
inevitable
Comparison of Pulmonary
Variables
Neonate Infant
5 Years of
Age
Adult
Weight (kg)
3
4-10
18
70
Breathing frequency (breaths/min)
35
24-30
20
15
Tidal volume (mL/kg)
6
6
6
6
Vital capacity (mL/kg)
35
70
Alveolar ventilation (mL/kg/min)
130
60
Carbon dioxide production
(ml/kg/min)
6
3
Functional residual capacity
(mL/kg)
25
25
35
40
RIB CAGE
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The compliant rib cage of a newborn produces a
mechanical disadvantage to effective ventilation
The negative intrapleural pressure produced by
normal inspiratory effort tends to collapse the
cartilaginous, compliant chest of an infant
(especially a premature newborn), which causes
paradoxical chest wall motion and limits airflow
during inspiration
The circular configuration of the rib cage (ellipsoid
in adults) and the horizontal angle of insertion of
the diaphragm (oblique in adults) cause distortion
of a newborn's rib cage and inefficient
diaphragmatic contraction.
DIAPHRAGM
An adult diaphragm contains 55% type I
fibers (fatigue resistant, slow-twitching,
highly oxidative fibers), whereas the
diaphragm of a full-term infant has 25%
and that of a preterm infant has 10%
 A lower proportion of type I fibers
predisposes these primary respiratory
muscles to fatigue
 The intercostal muscles show a similar
developmental pattern
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PULMONARY SURFACTANT
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Pulmonary surfactant effects dramatic changes in
lung mechanics, including distensibility and endexpiratory volume stability
The development of respiratory distress syndrome
of the newborn correlates with insufficient (premature
infants) or delayed (infants of diabetic mothers)
synthesis of surfactant
The most significant decrease in infant mortality
observed in 20 years in the United States occurred
in 1990, the year that surfactant was released
commercially
However, chronic lung disease persists as a
common problem in approximately 20% of premature
infants as a result of the complex interplay of many
factors in addition to surfactant during normal growth
and development of the lungs
Circulatory System
FETAL CIRCULATION
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The fetal circulation is characterized by:
(1) increased pulmonary vascular resistance
(2) decreased pulmonary blood flow
(3) decreased systemic vascular resistance
(4) right-to-left blood flow through the
patent
ductus arteriosus and foramen
ovale
At birth, the onset of spontaneous ventilation and elimination
of the placental circulation decrease pulmonary vascular
resistance and increase pulmonary blood flow
Simultaneously, systemic vascular resistance increases, left
atrial pressure increases, the foramen ovale closes
functionally, and the right-to left shunting ceases
When anatomic closure is achieved and cardiac anatomy is
normal shunting through the ductus arteriosus is eliminated
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Arterial hypoxemia or acidosis in a newborn can
precipitate return to a fetal pattern of circulation
(pulmonary arterial vasoconstriction, pulmonary
hypertension, reduced pulmonary blood flow)
This combination leads to right atrial pressure
increasing above left atrial pressure and thereby
results in right-to-left shunting through the foramen
ovale and ductus arteriosus
This return to a fetal circulatory pattern, termed
persistent fetal circulation or persistent pulmonary
hypertension of the newborn, further exacerbates
the arterial hypoxemia and acidosis
MYOCARDIAL FUNCTION
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The relative noncompliance of the neonatal
heart implies a limited capacity to handle a
volume load or to increase stroke volume for
augmentation of cardiac output (or both)
Thus,
the
"Frank-Starling"
responses
considered to play a limited role, whereas the
heart rate is critical for maintaining cardiac
output in a newborn
Over the first months of life, myocardial
contractility gradually increases, which allows
cardiac output to be maintained over a wide
range of preload and after load
EVALUATIONOF CARDIOPULMONARY
FUNCTION
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The initial step in evaluating the cardiopulmonary
system of a newborn begins with the physical
examination
Skin color, capillary filling time, trends in blood
pressure, heart rate, intensity of peripheral pulses,
presence of a murmur or S3 or S4 heart sounds,
respiratory rate, effort, and breath sounds, as well as
decreased urine output or metabolic acidosis, should
be assessed
Interpretation of the electrocardiogram, chest
radiograph, and echocardiogram will allow rational
planning for intraoperative monitoring, selection of
anesthetic drugs, delivery of intravenous fluids,
postoperative recovery, and the extent of the
proposed surgical procedure (total correction or
staged procedure)
Comparison of Cardiovascular
Variables
Neonate Infant
5 Years of Adult
Age
Weight
3
4-10
18
70
Oxygen consumption
(mg/kg/min)
6
5
4
3
Systolic blood pressure (mm Hg)
65
90-95
95
120
Heart rate (beats/min)
130
120
90
80
Renal Function
Renal Function
Urine production increases from about 5
ml/hr at 20 weeks, to about 18 ml/hr at 30
weeks, to about 50 ml/hr at 40 weeks of
gestation
 Although the kidneys are not essential for
maintaining normal fluid and electrolyte
balance in a fetus, urine production
contributes to normal amniotic fluid volume
and is critical for normal pulmonary and
urinary tract development
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GLOMERULAR FILTRATION RATE
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The renal function of a newborn versus an
adult
is
characterized
by
a
decreased glomerular filtration rate (GFR),
decreased excretion of solid materials, and
decreased urine concentrating ability
The GFR increases with gestational age, and
by 34 to 36 weeks of gestation, values are
similar to those reported for full-term infants
Over the first 3 months of life, the GFR
increases twofold to threefold
A slower rise is noted until adult values are
reached by 12 to 24 months of life
RENAL TUBULAR FUNCTION
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Limited renal tubular reabsorptive function is the
basis for the loss of bicarbonate and the "normal"
acidosis that occur in a newborn, particularly
premature newborns (sometimes called renal tubular
acidosis type 4)
Similarly, proximal renal tubular reabsorption of
sodium increases with gestational age
Of note, arterial hypoxemia, respiratory distress, and
hyper bilirubinemia can increase fractional sodium
excretion
The limited distal renal tubular function also impairs
the ability of the kidneys to excrete a sodium load. In
addition, tubular immaturity affects the conservation
of amino acids, nucleosides, glucose, and other
essential substrates
Hematology
Hematology
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At birth, a full-term newborn normally has a hemoglobin concentration of
18 to 20 g/dl
a preterm infant usually has a lower hemoglobin concentration ranging
between 13 and 15 g/dl (Tables)
Approximately 70% to 80% of the hemoglobin at birth is fetal hemoglobin
(HgF), but the concentration of HgF decreases to physiologically
insignificant levels by 3 to 6 months of age
The high affinity of HgF for oxygen shifts the oxyhemoglobin dissociation
curve to the left so that P 50(normally 18 to 20 mm Hg) is less than the
adult value (27 mm Hg)
Although high oxygen affinity improves the fetus's ability to uptake oxygen
from the mother at the placental interface, after birth this same high affinity
decreases the amount of oxygen released at tissue levels.
In a normal newborn, higher hemoglobin levels, greater blood volume, and
increased cardiac output (per unit weight) compensate adequately for HgF
Such normal, term infants tolerate the gradual decrease in hematocrit
(and HgF) over the first few months of life, with the nadir reaching values
as low as 9 to 10 g/dl
By comparison, the concentration of hemoglobin in a very-Iow-birthweight (VLBW, 1 500 g) or extremely-low-birth-weight (ELBW, <1000 g)
infant at birth normally ranges between 13 and 15 g/dl
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Of note, the nadir of a premature (<30 weeks' gestation) infant's
hemoglobin may be as low as 6 to 7 g/dl by 3 to 4 months of age
Erythropoietin is now routinely administered to infants in the
neonatal intensive care unit, thereby avoiding such profound
anemia
Newborns with cardiovascular or respiratory instability often benefit
from a hematocrit higher than 40% to 45% to facilitate adequate
oxygen delivery
Blood loss exceeding 10% to 15% of blood volume (or even less in
some patients) may not be tolerated by newborns, especially VLBW
infants
Cross-matched blood should be available for surgery in a newborn,
especially when blood loss is anticipated
Assessment of clotting function should be considered before major
surgery in a newborn because the synthesis of prothrombin and
factors II, VII, and X is limited in an immature liver
Perinatal asphyxia and septicemia affect the function and
concentration of both clotting factors and platelet count and thereby
result in coagulopathies
Before surgical intervention, the availability of fresh frozen plasma,
fibrinogen, and platelets must be considered
Hematologic Values in Children
Age
Hemoglobin (g/100 mL) (Mean)
Platelets (/mm3)
26-27 weeks
13.4
254,000
28 weeks
14.5
275,000
32 weeks
15.0
290,000
Term (cord)
16.5
290,000
1-3 days
18.5
192,000
2 weeks
16.6
252,000
1 month
13.9
250,000
2 months
11.2
200,000-250,000
6 months
12.6
150,000-350,000
6-24 months
12.0
150,000-350,000
2-6 years
12.5
150,000-350,000
6-12 years
13.5
150,000-350,000
12-18 years (male)
14.5
150,000-350,000
12-18 years (female)
14. 0
150,000-350,000
Adult male
15.5
150,000-350,000
Adult female
14.0
150,000-350,000
Developmental Changes in Blood
Volume
Age
Blood Volume (ml/kg)
Preterm infant
90-105
Term infant
78-86
1-12 months
73-78
1-3 years
74-82
4-6 years
80-86
7-18 years
83-90
Adults
68-88
MEDICAL AND SURGICAL
DISEASES THAT
AFFECT THE NEWBORN
Necrotizing Enterocolitis
Necrotizing
enterocolitis
(NEC)
is
a
gastrointestinal emergency that primarily affects
premature infants younger than 32 weeks'
gestational age
 NEC is a systemic process primarily related to
the sepsis that accompanies intestinal necrosis
and increased mucosal permeability
 The most common anatomic site is the ileocolic
region, but NEC is frequently discontinuous and
involves both the small and large intestine (Fig)
 The primary pathologic finding in NEC is
coagulative
or ischemic
necrosis, but
inflammation is also prominent
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CLINICAL MANIFESTATIONS
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Typically, a preterm baby in whom NEC develops has a
history
of
perinatal
asphyxia
or
postnatal
cardiorespiratory instability and manifests gastrointestinal
signs between the 1st and 10th days of life (abdominal
distention, retained gastric secretions that may be bile
tinged, vomiting, bloody or mucoid diarrhea, and occult
blood loss in stools)
Bowel necrosis and perforation may develop and be
accompanied by sepsis with thermal instability, lethargy,
metabolic acidosis, hypotension, hypoxia, jaundice,
disseminated intravascular coagulation(DIC), and
generalized bleeding
Most infants with NEC have a decreased platelet count
(50,000
to
75,OOO/mm3)
and
prolonged
prothrombin(PT) and partial thromboplastin times(PTT)
Abdominal radiographs may reveal dilated, fixed
(adynamic ileus) loops of bowel, gas in the portal venous
system, and pneumoperitoneum
TREATMENT
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Unless there is evidence of intestinal necrosis or
perforation, the initial treatment of NEC is
nonoperative and includes:
- decompression of the stomach
- cessation of feeding
- broad-spectrum antibiotics
- fluid and electrolyte therapy
- parenteral nutrition
- correction of hematologic abnormalities
Inotropic drugs may be needed to maintain
hemodynamic stability
Bowel perforation is the most important indication for
surgery
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Other events that increase the likelihood for
surgical intervention include:
- peritonitis
- air in the portal system
- bowel wall edema
- ascites
-progressively
deteriorating
hemodynamic
status
MANAGEMENT OF ANESTHESIA
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The preoperative assessment of infants with NEC should focus on
evaluating and correcting the respiratory, circulatory, metabolic, and
hematologic disorders
During fluid resuscitation these infants must be monitored carefully
for signs of patent ductus arteriosus or congestive heart failure
Most require mechanical ventilatory support because of metabolic
acidosis and respiratory complications of fluid administration and
sepsis
Depending on the hemodynamic status of the infant, intraoperative
monitoring may include continuous monitoring of intra-arterial and
central venous pressure and blood gas analysis
At a minimum, intravenous access should be adequate to allow
vigorous crystalloid and colloid administration
Fresh frozen plasma)FFP), platelets, and red blood cells may be
administered early in surgery in response to blood loss,
hemodynamic instability, or coagulopathy
In preterm infants, inspired oxygen concentrations should be
adjusted to produce a Pao₂ of 50 to 70 mm Hg (Spo₂ of90% to 95%)
Nitrous oxide should be avoided, especially in the presence of free
air in the gastrointestinal and portal venous systems
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Volatile anesthetics are often poorly tolerated and should
be introduced only in low concentrations to supplement
intravenous drugs (opioids, ketamine)
Fentanyl or remifentanil combined with low doses of
volatile anesthetics can provide analgesia and amnesia
and allow cardiovascular stability
Neuromuscular blocking drugs facilitate surgical exposure
Inotropes are occasionally needed to support the
cardiovascular system when fluid therapy alone fails to
maintain adequate perfusion
Observing bowel perfusion during surgery may provide a
useful guide to the effectiveness of fluid and inotropic
support
Postoperatively, mechanical ventilation and cardiovascular
support are usually required in the neonatal intensive care
unit(NICU)
Parenteral nutrition is essential after sepsis is controlled
and metabolic stability is established
Abdominal Wall Defects
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Omphalocele and gastroschisis are distinct lesions
despite a similar physical appearance (Figs)
Omphalocele is a central defect of the umbilical ring,
and the abdominal contents are within a sac, unless
the sac ruptures in utero
Gastroschisis is an abdominal wall defect, usually to
the right of the umbilical cord
This defect is generally larger than 5 cm in diameter
and typically contains only large and small bowel
(rarely the liver may exit through the defect)
The bowel is exposed to the intrauterine environment
with no sac, so the loops are matted, thickened, and
often covered with an inflammatory coating or peel
This anatomic defect can be diagnosed in utero with
fetal ultrasound
TREATMENT
Preoperative management of abdominal wall
defects is directed primarily toward fluid
resuscitation and minimizing heat loss, treating
sepsis, avoiding direct trauma to the herniated
organs, and identifying other anomalies
 A bowel bag may be used to minimize fluid
and heat loss
 Decompression of the stomach with an
orogastric or nasogastric tube is important to
prevent regurgitation, aspiration pneumonia,
and further bowel distention
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Fluid Therapy
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Intravenous fluid therapy (as much as two to four
times [150 to 300 ml/kg/day] the usual
maintenance infusion rate [80 to 100 ml/kg/day]) is
infused to ensure adequate hydration and to
compensate for peritonitis, bowel ischemia, and
significant third-space loss
Initially, a balanced salt solution is used, and
urine output is monitored
Urine output of 1 to 2 ml/kg/hr suggests adequate
hydration
Because of the large fluid requirements, acidbase status and electrolyte levels should be
monitored
Rarely, colloid is required to maintain
hemodynamic stability preoperatively
Surgical Treatment






Surgical management is aimed at repairing the abdominal
wall defect and reducing the protruded viscera
Forcing the viscera into an underdeveloped abdominal cavity
that cannot easily accommodate the herniated bowel can
have dramatic effects on ventilation and oxygenation, as well
as on cardiac output and systemic blood pressure
(secondary to impaired venous return from the inferior vena
cava)
Excessive compression of the intestine can produce
ischemia
Thus, during abdominal closure, the anesthesiologist must
anticipate the potential effects of decreased pulmonary
compliance (increased airway pressure, decreased oxygen
saturation, hypercapnia) and inadequate cardiac output
If primary closure is not possible, a Silastic mesh prosthesis
("silo") is sutured to the fascia of the defect
After the silo is in place, the extra-abdominal organs are then
gradually returned to the peritoneal cavity over a period of 3
to 10 days
Management of Anesthesia






Depending on the size of the defect, the anticipated difficulty
with closure, and the preoperative status of the infant,
continuous invasive monitoring of arterial and central venous
pressure may be indicated
Vigorous fluid therapy (10 to 100 ml/kg/hr) is often critical to
maintain perfusion and hemodynamic stability, but glucose
should be delivered at maintenance rates (3 to 4 mg/kg/min)
Heat loss should be minimized and a warm environment
maintained
Neuromuscular blockade is essential to maximize efforts for
primary closure of the abdomen
The inspired oxygen concentration must be adjusted to
maintain oxygen saturation between 95% and 97% while
recognizing that the physiologic range of Pao₂ in newborns
is 50 to 70 mm Hg
Nitrous oxide may increase bowel distention and is therefore
avoided
A variety of combinations of intravenous
drugs and volatile anesthetics can provide
adequate surgical conditions
 High doses of opioids are acceptable
because except in infants with a small defect,
mechanical ventilation of the lungs must be
maintained postoperatively
 Prolonged postoperative total parenteral
nutrition(TPN) is generally required, especially
in infants with a large omphalocele or
gastroschisis, so appropriate intravenous
access should be established in the operating
room to facilitate early postoperative
nutritional support

Tracheoesophageal Fistula







Different anatomic variations of tracheoesophageal fistula (TEF)
occur, and in most cases (type B, C, E), TEF and esophageal atresia
occur together (Fig)
The most common lesion (>90%) is type C, in which a fistula exists
between the trachea and the lower esophageal segment at a point
slightly above the carina, whereas the upper esophageal segment
ends blindly in the mediastinum at the level of the second or third
thoracic vertebra
Approximately 20% to 25% of these infants also have a congenital
heart defect (ventricular septal defect, atrial septal defect, tetralogy of
Fallot, atrioventricular canal, coarctation of the aorta), and about 20%
to 30% are born prematurely
The acronym VATER refers to a group of anomalies including V,
vertebral defects; A, anal defects; TE, tracheoesophageal atresia;
and R, renal anomalies.
Another acronym includes a C and L because cardiac and limb
anomalies are also common
As many as 20% to 25% of infants with esophageal atresia will have
at least three of the defects included in VACTERL
Between 50% and 65% of infants with esophageal atresia with or
without TEF will have at least one additional anomaly
Type C (86%) is esophageal atresia with a distal TEF
Type A (8%) is esophageal atresia without a TEF
Type E (4%) is an H-type fistula without esophageal atresia
Type D (1%) is esophageal atresia with both proximal and
distal TEF
Type B (1%) is esophageal atresia with a proximal TEF
TREATMENT




Surgical ligation of a TEF is performed promptly
Optimally, the surgical repair can be accomplished
as a one-stage procedure in which the fistula is
ligated and the esophagus is primarily
anastomosed
In infants with significant associated anomalies or
sepsis, a thoracotomy may be considered too risky,
and instead, a palliative procedure (gastrostomy) is
performed under local or general anesthesia and
the definitive repair performed within 24 to 72
hours, when the extent of other anomalies is
defined, cardiovascular stability is established, and
a clear surgical plan has been defined
Often, the gastrostomy tube is kept patent to
decompress
the
stomach
and
minimize
regurgitation into the lungs
Interventions to Protect the Lungs from Aspiration in
the Presence of a Tracheoesophageal Fistula(TEF)
Avoidance of feedings
Upright positioning of the infant to decrease the likelihood of gastroesophageal reflux
Intermittent suctioning of the upper blind esophageal pouch
Antibiotic therapy and physiotherapy if pneumonia is diagnosed
MANAGEMENTOF ANESTHESIA






Awake tracheal intubation is likely to be considered the safest approach
to secure the airway in infants with TEF
It allows appropriate positioning of the endotracheal tube without
positive-pressure ventilation, as well as minimizes the risk for gastric
distention from inspired gases passing through the fistula during
positive-pressure ventilation of the newborn's lungs
Titrating small doses of fentanyl (0.2 to 0.5 чg/kg IV) or morphine (0.02
to 0.05 mg/kg IV) before tracheal intubation may be helpful, but this
must be considered from the perspective of the infant's clinical status at
the time of the procedure
An alternative to awake tracheal intubation is inhalation induction of
anesthesia (after pharyngeal suctioning), with or without a
neuromuscular blocking drug, plus gentle positive-pressure ventilation
of the infants' lungs.
After the endotracheal tube is in place, end-tidal carbon dioxide and
oxygen saturation are monitored and the stomach and chest
auscultated to ensure that the lungs are adequately ventilated and the
stomach is not being inflated with inspired gas
Blood clots or secretions may block the endotracheal tube, and thus
frequent suctioning is usually required








After the TEF is ligated, a catheter passed through the nose or
mouth by the anesthesiologist into the blind upper pouch
identifies the upper esophageal structure
The surgeon passes a catheter into the lower part of the
esophagus, and the anastomosis is fashioned over the catheter
When the anastomosis is complete, the catheter is withdrawn to
just above the suture line, and the proximal end of the catheter is
marked at the mouth
The distance from the mouth to the distal tip is noted
Only catheters of this length or shorter should be used to suction
postoperatively
Some term infants can be extubated after simple ligation of a
TEF, but more often postoperative ventilation is maintained for at
least 24 to 48 hours
Tracheomalacia or a defective tracheal wall at the site of the
fistula is common and can predispose to collapse of the airway
during spontaneous ventilation
Most surgeons recommend that ventilation with a mask and bag
be avoided for at least several days after an esophageal
anastomosis
PERSISTENT EFFECTS AFTER
SURGICAL REPAIR





TEF cannot be considered a simple anatomic
problem cured by a surgical intervention
Many patients have anatomic narrowing of the
esophagus at the site of anastomosis or ligation of
the fistula, and this narrowing may progress to a
severe stricture
Esophageal dysmotility and reflux are common
and may also lead to esophageal stricture
Recurrent upper and lower respiratory infections
occur in 35% to 75% of patients
Pulmonary function studies 7 to 18 years after
repair show a high incidence of obstructive and
restrictive forms of lung disease
Congenital Diaphragmatic Hernia
Congenital diaphragmatic hernia (CDH) is a
defect in the diaphragm that develops early in
gestation and is accompanied by extrusion of
intra-abdominal organs into the thoracic cavity
and other associated abnormalities(Table &Fig)
 In many infants with CDH, the herniated
abdominal viscera that occupy the thoracic
cage interfere with development of the lungs
 Typically,
some degree of pulmonary
hypoplasia is present on the ipsilateral side,
but often also on the contralateral side

Abnormalities That May Be Associated with
Congenital Diaphragmatic Hernia
Bilateral lung hypoplasia (varying degrees)
Pulmonary hypertension
Pulmonary arteriolar hyperreactivity and arteriolar reactivity
Congenital anomalies
Cardiac
Chromosomal
CLINICAL MANIFESTATIONS



The classic triad of CDH consists of cyanosis,
dyspnea, and apparent dextrocardia
Physical examination reveals
a scaphoid abdomen,
bulging chest,
decreased breath sounds,
distant or right-displaced heart sounds,
and bowel sounds in the chest
Radiographs may show a bowel gas pattern in
the chest, mediastinal shift, and minimal lung
tissue at the left costophrenic sulcus
TREATMENT





The goal of initial management of CDH is to avoid a
surgical intervention when the infant is hypoxic and acidotic
Instead, medical management is directed to stabilizing the
infant's cardiorespiratory status by improving oxygenation,
correcting metabolic acidosis, reducing the right-to-left
shunting, and increasing pulmonary perfusion
Positive-pressure ventilation with a facemask is particularly
risky for infants with CDH because attempting to expand
the noncompliant lungs may distend the stomach and
intestines, which are in the left thoracic cavity, and thereby
further decrease chest compliance
Early tracheal intubation and decompression of the
stomach are important initial steps to prevent further
compression of the infant's lungs by the displaced
abdominal viscera
In the early neonatal period, some infants exhibit a
honeymoon period characterized by adequate oxygenation
and ventilation with minimal ventilatory support


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
However, this period is often followed by a sudden and
often unexplained return to a state of persistent pulmonary
hypertension (persistent fetal circulation) and clinical
deterioration (acidosis, arterial hypoxemia, hypercapnia,
pulmonary hypertension, and right -to-left shunting through
the foramen ovale and ductus arteriosus)
Efforts at manipulating pulmonary vascular resistance
(pharmacologic means or hyperventilation, or both) are not
predictably successful
If conventional mechanical ventilation of the infant's lungs is
not effective, a trial of high-frequency oscillatory support
may be considered
Other therapeutic interventions to consider include the
administration of inhaled nitric oxide and extracorporeal
membrane
oxygenation
(ECMO)
to
achieve
cardiorespiratory stability before surgery
If an infant does require either nitric oxide or ECMO,
surgery is likely to be performed in the neonatal intensive
care unit(NICU) so that these therapies can be maintained
MANAGEMENT OF ANESTHESIA
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

Usually, surgical repair is approached through an
abdominal
incision,
but
a
transthoracic
or
thoracoabdominal approach is also possible
With rare exception, infants with a moderate or large
CDH require ventilatory support preoperatively, and
most receive neuromuscular blockade
The goals of ventilation in the operating room (optimize
PH and pulmonary blood flow with minimal barotrauma)
are the same as preoperatively
Hyperventilation of the infant's lungs is reserved to
treat acute episodes of pulmonary hypertension
If sudden deterioration in ventilation or hemodynamic
status (or both) occurs, pulmonary hypertension must
be quickly differentiated from a contralateral
pneumothorax because treatment of pneumothorax is
needle thoracostomy and chest tube placement rather
than hyperventilation




The selection of specific anesthetic drugs is logically
based on cardiorespiratory status, the site of surgical
repair (neonatal intensive care nursery or operating
room), and the plans for intraoperative ventilatory
support
Nitrous oxide is avoided in infants with CDH because
most require high inspired oxygen concentrations and
nitrous oxide can diffuse inside the viscera and
exaggerate lung compression
If an anesthesia machine is available, a low
concentration of a volatile anesthetic can be
administered and the dose increased if the newborn is
hemodynamically stable
In most cases, opioids (usually intravenous fentanyl)
are administered and an opioid infusion is continued into
the postoperative period
Myelomeningocele
The
primary
defect
in
a
myelomeningocele is localized failure of
the neural tube to close
 The lesion appears most often in the
lumbar area as a sac on the back of the
infant
 In addition, because the vertebral
arches in the area fail to fuse or are
totally absent, the spinal canal is
widened

CLINICAL MANIFESTATIONS
The
clinical
manifestations
of
myelomeningocele
relate
to
the level of neural tube involvement,
the existence of other neurologic anomalies,
and the development of hydrocephalus
(develops in about 90% of infants with
thoracolumbar, lumbar, or lumbosacral
lesions)
 In addition, the Arnold-Chiari malformation is
identified in most infants with this lesion

TREATMENT
 Treatment of myelomeningocele








is based on the predicted
prognosis
In some infants, supportive care is an appropriate level of
conservative intervention
In many infants, prenatal diagnosis introduces the consideration of
fetal treatment or cesarean section, or both, to avoid trauma during
spontaneous vaginal delivery
In most cases of thoracolumbar, lumbar, and lumbosacral lesions,
surgical intervention is initiated in the first 24 hours of life
Early surgical treatment decreases the incidence of infection and
further neurologic injury
The main anesthetic considerations are related to avoiding injury
during induction and tracheal intubation and meticulous attention to
ventilation in the prone position
The infant can be supported on "bolsters" while supine during
induction and again when positioned prone for surgical treatment
Placement of a ventriculoperitoneal shunt is generally performed in
a separate surgery
The need for frequent surgical interventions is the basis for
initiating latex precautions from the neonatal period in the hope of
minimizing the risk for development of latex allergy
Pyloric Stenosis

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

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

The abnormal anatomy leading to pyloric stenosIs is thickened
circular smooth muscle of the pylorus
The gastric outlet gradually becomes obstructed over the first
days to weeks of life and leads to projectile, nonbilious vomiting
and failure to thrive, with body weight less than birth weight at 2
to 3 weeks of age
The pathognomonic physical finding is an olive-sized mass in the
upper left to midportion of the abdomen
The condition is more common in white, first-born males
The most significant preoperative considerations are fluid and
electrolyte imbalance and a full stomach
Because of recurrent vomiting of acidic gastric fluid, hypokalemic
hypochloremic metabolic alkalosis and dehydration may develop
Administration of intravenous fluids allows rehydration and
correction of the metabolic abnormalities within 6 to 12 hours in
most infants
At that point, surgical treatment is indicated
MANAGEMENTOF ANESTHESIA

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


Some anesthesiologist prefer to consider an infant as having a
full stomach and recommend a rapid-sequence induction of
anesthesia after emptying the stomach with a nasogastric tube
Others suggest that the stomach empties spontaneously and
believe that a inhalational or intravenous (not necessarily
rapid-sequence) induction of anesthesia is acceptable
A history of a barium swallow may affect the decision
regarding the technique for induction of anesthesia.
However, sonography and not a barium swallow is the most
frequent technique for confirming the diagnosis of pyloric
stenosis
Although the surgical procedure is a simple pyloromyotomy
that takes only about 15 minutes, the current trend is to
perform a laparoscopic procedure to minimize recovery time
and the likelihood of ileus
The infant may be able to eat within several hours of surgery,
and discharge is often possible within about 12 hours
COMPLICATING ISSUES IN THE
CLINICAL
MANAGEMENT OF PEDIATRIC
PATIENTS
Upper Respiratory Infection






URI has diffuse effects on the respiratory epithelium,
mucociliary function, and airway reactivity
These effects combine to provide the potential for an
increased risk for anesthesia in specific clinical
settings
If the planned surgical procedure is short and airway
support is restricted to the use of a facemask, the risk
for an adverse respiratory event is minimal
If an endotracheal tube is required, the risk for an
adverse respiratory event is increased (up to 10- fold)
over that in an infant without a URI whose trachea is
not intubated
An LMA seems to be associated with risks midway
between those associated with a facemask and those
with an endotracheal tube
Younger age plus a URI seems to be associated with
an increased risk from anesthesia






URIs develop recurrently in 1- to 6-year-olds, and if
reactive airways accompany the infection, the effect on
the airway persists for 2 to 6 weeks
The decision to cancel surgery on a child with an
uncomplicated URI always requires assessment from the
viewpoint of a specific patient and family, a specific
procedure, and a specific surgeon
A strict protocol for when to cancel surgery is impractical
The patient's age, medical and anesthetic history,
current
physical
examination,
planned
surgery
(placement of tympanostomy tubes versus surgery for
craniofacial repair), and anticipated postoperative care
(need for mechanical ventilatory support) must be
analyzed
Ultimately, the preoperative evaluation must weigh the
inconvenience of rescheduling against ignoring possible
risks
If the decision is to proceed with elective surgery, the
infant should be considered to have reactive airways
OUTPATIENT SURGERY




Inguinal herniorrhaphy, hypospadias repair, and
various orthopedic procedures are commonly
performed in young children as outpatient surgery
The use of an LMA plus a caudal block (1 mg/kg of
0.125% to 0.25% bupivacaine or ropivacaine)
provides excellent postoperative pain control while
decreasing intraoperative anesthetic requirements
The more dilute local anesthetic solution may be of
benefit to ambulatory children by avoiding significant
motor blockade
Laparoscopic inguinal hernia repair, unlike an open
repair, generally requires endotracheal intubation,
and caudal anesthesia is not needed.
Preoperative Medication in
Children
Oral
Midazolam (mg/kg)
Nasal
0.5-1.0
Intravenous
0.05-0.1
Fentanyl (µg/kg)
1-3
Morphine (mg/kg)
0.05-0.1
Sufentanil (µg/kg)
0.25-0.5
EX-PREMATURE INFANT







Despite many studies dealing with postoperative apnea in
ex-premature infants, a precise protocol defining the need for
postoperative monitoring cannot be developed “
This may reflect the difficulty in defining an ex-premature infant
For example, a 36-week-gestation infant who had an unremarkable
3-day stay in the intensive care nursery is distinct from a 28-weekgestation infant who had NEC, respiratory insufficiency, and chronic
lung disease and is continuing oxygen therapy and diuretics at
home.
Furthermore, although apnea is rare after about 48 weeks‘
postconceptual age, the incidence is not zero
Even the definition of apnea varies from study to study
Thus, the decision to admit an ex-premature infant after surgery
requires individual assessment of the patient, consideration of the
surgical procedure, and the time when the surgery is completed
(early morning, late afternoon)
The most conservative approach is to admit every expremature
infant who is younger than 60 weeks' postconceptual age, but this
is impractical in many cases
In addition to the potential risk for postoperative
apnea, ex-premature infants commonly have
chronic lung conditions characterized by
reactive airways disease and abnormal
pulmonary function for the first decade of life, if
not longer
 Developmental delay may affect plans for
premedication
and
may
contribute
to
unexpected responses to sedatives and
anesthetics
 Hepatic and renal dysfunction is not uncommon
