Dr. Moayed – Lecture 1
Pediatric Surgery
Fifth Stage
I. INTRODUCTION
A. Neonatal Physiologic Characteristics
1. Water metabolism
Water represents 70 to 80% of the body weight of the normal neonate and
premature baby respectively. Total body water (TBW) varies inversely with fat content,
and prematures have less fat deposits. TBW is distributed into extracellular fluid (ECF)
and intracellular fluid (ICF) compartment. The ECF compartment is one-third the TBW
with sodium as principal cation, and chloride and bicarbonate as anions. The ICF
compartment is two-third the TBW with potassium the principal cation. The Newborn's
metabolic rate is high and extra energy is needed for maintenance of body temperature
and growth. A change in body water occurs upon entrance of the fetus to his new
extrauterine existence. There is a gradual decrease in body water and the extracellular
fluid compartment with a concomitant increase in the intracellular fluid compartment. This
shift is interrupted with a premature birth. The newborn's body surface area is relatively
much greater than the adults and heat loss is a major factor. Insensible water loss are
from the lung (1/3) and skin (2/3). Transepithelial (skin) water is the major component
and decreases with increase in post-natal age. Insensible water loss is affected by
gestational age, body temperature (radiant warmers), and phototherapy.
Neonatal renal function is generally adequate to meet the needs of the normal full-term
infant but may be limited during periods of stress. Renal characteristics of newborns are
a low glomerular filtration rate and concentration ability (limited urea in medullary
interticium) which makes them less tolerant to dehydration. The neonate is metabolically
active and production of solute to excrete in the urine is high. The kidney in the newborn
can only concentrate to about 400 mOsm/L initially (500-600 mOsm/L the full-term
compared to 1200 mOsm/L for an adult), and therefore requires 2-4 cc/kg/hr urine
production to clear the renal solute load. The older child needs about 1-2 cc/kg/hr and the
adult 0.5-1 cc/kg/hr.
2. Fluid and Electrolytes Concepts
Cellular energy mediated active transport of electrolytes along membranes is the
most important mechanism of achieving and maintaining normal volume and composition
of fluid compartments. Infants can retain sodium but cannot excrete excessive sodium.
Electrolytes requirements of the full-term neonate are: Sodium 2-3 meq/kg/day,
potassium 1-2 meq/kg/day, chloride 3-5 meq/kg/day at a rate of fluid of 100 cc/kg/24 hrs
for the first 10 kg of weight. As a rule of thumb, the daily fluid requirements can be
approximated too:
Prematures 120-150 cc/kg/24 hrs
Neonates (term) 100 cc/kg/24 hrs
Infants >10 kg 1000 cc+ 50 cc/kg/24 hrs.
Special need of preterm babies’ fluid therapy is: conservative approach, consider
body weight changes, sodium balance and ECF tonicity. They are susceptible to both
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sodium loss and sodium and volume overloading. High intravenous therapy can lead to
patent PDA, bronchopulmonary dysplasia, enterocolitis and intraventricular hemorrhage.
Impaired ability to excrete a sodium load that can be amplifies with surgical stress
(progressive renal retention of sodium). Estimations of daily fluid requirements should
take into consideration:
(1) urinary water losses, (2) gastrointestinal losses, (3) insensible water losses, and (4)
surgical losses (drains).
Blood Volumes estimates of help during surgical blood loss are: premature 85-100
cc/kg, term 85 cc/kg, and infant 70-80 cc/kg. The degree of dehydration can be measured
by clinical parameters such as: body weight, tissue turgor, state of peripheral circulation,
depression of fontanelle, dryness of the mouth and urine output. Intravenous nutrition is
one of the major advances in neonatal surgery and will be required when it is obvious that
the period of starvation will go beyond five days.
Oral feeding is the best method and breast is best source. Newborn infants require
100-200 calories/kg/day for normal growth. This is increased during stress, cold, infection,
surgery and trauma. Minimum daily requirement are 2-3 gm/kg of protein, 10-15 gm/kg
of carbohydrate and small amount of essential fatty acids.
B. Variations in Individual Newborns
1. Types of Newborns Infants
a) The full-term, full-size infant with a gestational age of 38 weeks and a body
weight greater than 2500 grams (TAGA)- they received adequate intrauterine nutrition,
passed all fetal tasks and their physiologic functions are predictable. b) The preterm infant
with a gestational age below 38 weeks and a birth weight appropriate for that age
(PreTAGA); c) The small-for-gestational-age infant (SGA) with a gestational age over 38
weeks and a body weight below 2500 grams- has suffered growth retardation in utero. d)
A combination of (b) and (c), i.e., the preterm infant who is also small for gestational age.
The characteristic that most significantly affects the survival of the preterm infant
is the immature state of the respiratory system. Between 27 and 28 weeks of gestation
(900-1000 grams), anatomic lung development has progressed to the extent that
extrauterine survival is possible. It is only after 30 to 32 weeks of gestation that true
alveoli are present. Once there is adequate lung tissue, the critical factor that decides
extrauterine adaptation and survival of the preterm infant is his capabilities to produce
the phospholipid-rich material, surfactant that lines the respiratory epithelium.
2. Metabolic and Host Defenses
Handling of the breakdown products of hemoglobin is also a difficult task for the
premature infant. The ability of the immature liver to conjugate bilirubin is reduced, the
life span of the red blood cell is short, and the bilirubin load presented to the circulation
via the enterohepatic route is increased. "Physiologic" jaundice is, therefore, higher in the
preterm infant and persists for a longer period. Unfortunately, the immature brain has an
increased susceptibility to the neurotoxic effects of high levels of unconjugated bilirubin,
and kernicterus can develop in the preterm baby at a relatively low level of bilirubin.
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Other problems affecting the baby include the rapid development of hypoglycemia
(35 mg %), hypocalcemia and hypothermia. Newborn have a poorly developed
gluconeogenesis system, and depends on glycolysis from liver glycogen stores (depleted
2-3 hrs after birth) and enteral nutrition. Immature infants can develop hyperglycemia
from reduced insulin response to glucose causing intraventricular hemorrhage and
glycosuria. The preterm and surgical neonate is more prone to hypocalcemia due to
reduced stores, renal immaturity, and relative hypoparathyroidism (high fetal calcium
levels). Symptoms are jitteriness and seizures with increase muscle tone. Calcium
maintenance is 50 mg/kg/day.
Human beings are homeothermic organisms because of thermoregulation. This
equilibrium is maintained by a delicate balance between heat produced and heal lost.
Heat production mechanisms are: voluntary muscle activity increasing metabolic
demands, involuntary muscle activity (shivering) and nonshivering (metabolizing brown
fat). Heat loss occurs from heat flow from center of the body to the surface and from the
surface to the environment by evaporation, conduction, convection and radiation. There
is an association between hypothermia and mortality in the NICU's. The surgical neonate
is prone to hypothermia.
Infant produce heat by increasing metabolic activity and using brown fat. Below the 35°C
the newborn experiences lassitude, depressed respiration, bradycardia, metabolic
acidosis, hypoglycemia, hyperkalemia, elevated BUN and oliguria (neonatal cold injury
syndrome). Factors that precipitate further these problems are: prematurity, prolonged
surgery, and eviscerated bowel (gastroschisis). Practical considerations to maintain
temperature control are the use of humidified and heated inhalant gases during
anesthesia, and during all NICU procedures use radiant heater with skin thermistor-
activated servo-control mechanism.
The newborn's host defenses against infection are generally sufficient to meet the
challenge of most moderate bacterial insults, but may not be able to meet a major insult.
Total complement activity is 50% of adult’s levels. C3, C4, C5 complex, factor B, and
properdin concentration is also low in comparison to the adult. IgM, since it does not pass
the placenta, is absent.
3- Surgical Response of Newborns
The endocrine and metabolic response to surgical stress in newborns (NB) is
characterized by catabolic metabolism. An initial elevation in catecholamines, cortisol and
endorphins upon stimulation by noxious stimuli occurs; a defense mechanism of the
organism to mobilize stored energy reserves, form new ones and start cellular catabolism.
Cortisol circadian responsiveness during the first week of life is diminished, due to
inmaturation of the adrenal gland. Cortisol is responsible for protein breakdown, release
of gluconeogenic amino acids from muscle, and fat lipolysis with release of fatty acids.
Glucagon secretion is increased. Plasma insulin increase is a reflex to the hyperglycemic
effect, although a resistance to its anabolic function is present. During surgical stress NB
release glucose, fatty acids, ketone bodies, and amino acids; necessary to meet body
energy needs in time of increase metabolic demands. Early postoperative parenteral
nutrition can result in significant rate of weight gain due to solid tissue and water
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accumulation. Factors correlating with a prolonged catabolic response during surgery are:
the degree of neuroendocrinological maturation, duration of operation, amount of blood
loss, type of surgical procedure, extent of surgical trauma, and associated conditions
(hypothermia, prematurity, etc.). They could be detrimental due to the NB limited
reserves of nutrients, the high metabolic demands impose by growth, organ maturation
and adaptation after birth. Anesthetics such as halothane and fentanyl can suppress such
response in NB
II. HEAD AND NECK LESIONS
A. Cervical Lymphadenopathy
An enlarged lymph node is the most common neck mass in children. Most are
anterior to the sternocleidomastoid muscle. Infection is the usual cause of enlargement;
viral etiology and persist for months.
Acute suppurative submandibular adenitis occur in early childhood (6 mo-3 yrs), is
preceded by pharyngitis or URI, the child develops erythema, swelling and cellulitis, and
management is antibiotics and drainage. Chronic adenitis: persistent node (> 3 wk.,
tonsillar), solitary, non-tender, mobile and soft. Generally no tx if < 1 cm, for nodes above
2 cm sizes with rapid growth, clustered, hard or matted do biopsy.
Other causes are: (1) Mycobacterial adenitis- atypical (MAIS complex), swollen, non-
tender, nor-inflamed, positive skin test, excision is curative, chemotx is of no value. (2)
Cat-Scratch adenitis- caused by A. Fellis, transmitted by kittens, positive complement
fixation test, minimally tender, fluctuant regional nodes, spontaneous resolution. (3)
Hodgkin's disease mostly teenager and young adults, continuing growth, non-tender
node, associated to weight loss, biopsy is diagnostic.
B. Congenital Torticollis
Congenital muscular torticollis is a disorder characterize by shortening of the
cervical muscles, most commonly the sternocleidomastoid (SCM) muscle, and tilting of
the head to the opposite side. This is the result of endomysial fibrosis of the SCM muscle.
There is a relationship between birth position and the side affected by the contracture.
Congenital torticollis causes: plagiocephaly (a craniofacial deformity), fascial asymmetry
(hemihypoplasia), scoliosis and atrophy of the ipsilateral trapezius muscle if not corrected.
Torticollis can develop at any age, although is more common during the first six months
of life. The SCM muscle can be a fibrous mass, or a palpable tumor 1-3 cm in diameter
within the substance of the muscle is identified by two to three weeks of age. Management
is conservative in most cases using early physiotherapy exercises? a mean duration of
three months to achieve full passive neck range of motion. The severity of restriction of
motion is the strongest predictor of treatment duration. Those children with failed medical
therapy or the development of fascial hemihypoplasia should undergo surgical transection
of the SCM muscle.
C. Thyroglossal Duct Cysts
Thyroglossal duct cyst (TDC) is the most common congenital anterior midline neck
mass usually (2/3 of cases) presenting before the second decade of life. Symptoms appear
at an average age of four with the sudden appearance of a cystic mass at the angle of
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neck level moving with tongue protrusion and swallowing. Males are more commonly
affected than females. TDC is an embryologic anomaly arising from epithelial remnant left
after descent of the developing thyroid from the foramen cecum. The lining is cuboidal,
columnar or pseudostratified epithelium. TDC is associated to discomfort, infection and a
slight probability of malignancy.
A legally protective requirement is to document that the mass is not ectopic thyroid gland.
Diagnosis is physical. Sonograms will show a cyst between 0.4 and 4 cm in diameter, with
variable sonographic appearance and no correlation with pathological findings of infection
or inflammation. Once infected surgical excision is more difficult and recurrence will
increase. Management is Sistrunk operation: Excision of cyst with resection of duct along
with the central portion of hyoid bone (a minimum of 10-15 mm of hyoid bone should be
removed) and some muscle surrounding the proximal ductules (the length of single duct
above the hyoid bone spreads into many ductuli as it approach the foramen cecum).
Extensive dissection can cause pharyngodynia. The greatest opportunity for cure is
surgery at initial non-inflamed presentation. Inadequate excision is a risk factor for further
recurrence.
D. Branchial Cleft Fistulas
Branchial cleft fistulas (BCF) originate from the 1st to 3rd branchial apparatus
during embryogenesis of the head and neck. Anomalies of the 2nd branchial cleft are by
far the most commonly found. They can be a cyst, a sinus tract or fistulas. Fistulas (or
sinus tract if they end blindly) display themselves as small cutaneous opening along the
anterior lower third border of the sternocleidomastoid muscle, communicates proximally
with the tonsillar fossae, and can drain saliva or a mucoid secretion. Management consists
of excision since inefficient drainage may lead to infection. I have found that dissection
along the tract (up to the tonsillar fossa!) can be safely and easily accomplished after
probing the tract with a small guide wire in-place. This will prevent injury to nerves,
vessels and accomplish a pleasantly smaller scar. Occasionally a second stepladder
incision in the neck will be required. 1st BCF are uncommon, located at the angle of the
mandible, and communicating with the external auditory canal. They have a close
association with the fascial nerve. 3rd BCF are very rare, run into the piriform sinus and
may be a cause of acute thyroiditis or recurrent neck infections.
E. Cystic Hygroma
Cystic hygroma (CH) is an uncommon congenital lesion of the lymphatic system
appearing as a multilocular fluid filled cavity most commonly in the back neck region,
occasionally associated with extensive involvement of airway or vital structures. The
etiology is intrauterine failure of lymphatics to communicate with the venous system.
Prenatal diagnosis can be done during the first trimester of pregnancy as a huge neck
tumor. Differential diagnosis includes teratomas, encephalocele, hemangiomas, etc.
There is a strong correlation between prenatal dx and Turner's syndrome (> 50%),
structural defects (Noonan's syndrome) and chromosomic anomalies (13, 18, 21). Early
diagnosis (< 30 wk gestation) is commonly associated to those anomalies, non-immune
hydrops and dismal outcome (fetal death). Spontaneous regression is less likely but can
explain webbed neck of Turner and Noonan's children. Prenatal dx should be followed by
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cytogenetic analysis: chorionic villous sampling, amniocentesis, or nuchal fluid cell
obtained from the CH itself to determine fetal karyotype and provide counseling of
pregnancy. Late diagnosis (>30 wks) should be delivered in tertiary center prepare to
deal with dystocia and postnatal dyspnea of newborn. The airway should be secured
before cord clamping in huge lesions. Intracystic injection of OK432 (lyophilized product
of Streptococcus pyogenes) caused cystic (hygromas) lymphangiomas to become
inflamed and led to subsequent cure of the lesion without side effects.
III.OBSTRUCTIVE PROBLEMS
A. Esophageal Atresia a/o Tracheo-esophageal fistula
1. Embryology
The trachea and esophagus initially begin as a ventral diverticulum of the foregut
during the third intrauterine week of life. A proliferation of endodermal cells appears on
the lateral aspect of this growing diverticulum. These cell masses will divide the foregut
into trachea and esophageal tubes. Whether interruption of this normal event leads to
tracheo-esophageal anomalies or during tracheal growth atresia of the esophagus results
because of fistulous fixation of the esophagus to the trachea remnant to be proven.
2. Classification
EA with distal TEF (87% )- the most common anomaly, the NG tube coiled at T4-5
level and gas will be seen in the KUB. EA without TEF (8%) - pure esophageal atresia, NG
coiled at T4-5 level with airless abdomen. TEF without atresia (4%) - pure tracheo-
esophageal fistula. EA with proximal TEF (<1%). EA with proximal and distal TEF (<1%)
Congenital isolated tracheo-esophageal fistula (TEF) occurs as 4-6% of the disorders
of the esophagus bringing problems during early diagnosis and management. More than
H-type is N-type, due to the obliquity of the fistula from trachea (carina or main bronchi)
to esophageal side (see the figure) anatomically at the level of the neck root (C7-T1).
Pressure changes between both structures can cause entrance of air into the esophagus,
or esophageal content into the trachea. Thus, the clinical manifestation that we must be
aware for early diagnosis are: cyanosis, coughing and choking with feedings, recurrent
chest infections, persistent gastrointestinal distension with air, and hypersalivation.
Diagnosis is confirmed with a well-done esophagogram, or video-esophagogram (high
success rates, establish level of the TEF). Barium in the trachea could be caused by
aspiration during the procedure. Upon radiologic doubt bronchoscopy should be the next
diagnostic step. Any delay in surgery is generally due to delay in diagnosis rather than
delay in presentation. Management consists of surgical closure of the TEF through a right
cervical approach. Hint: a small guide-wire threaded through the fistula during
bronchoscopy may be of some help. Working in the tracheo-esophageal groove can cause
injury to the recurrent laryngeal nerve with vocal cord paralysis. Recurrence after closure
is rare.
3. Diagnostic characteristics:
The incidence is one in every 2500 live births. We see between 8-10 per year at the
University Pediatric Hospital. The mother might show polyhydramnios since the fetus is
unable to swallow amniotic fluid. (May be responsible for early delivery). Polyhydramnios
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is most commonly seen in pure esophageal atresia type. Choking, coughing and
regurgitation with first feed. Excessive salivation, cyanosis with feedings. Inability to pass
feeding tube into the stomach. Contrast studies (UGIS, esophagogram) are rarely needed,
and of potential disaster (aspiration of contrast material). Abdominal films should be
obtained to rule out the occurrence of associated gastrointestinal anomalies. Isolated TEF
is more difficult to diagnose and may require repeated lateral esophagograms,
bronchoscopy and esophagoscopy.
4. Management
Correct dehydration, acid-base disturbances, respiratory distress and decompress
proximal esophageal pouch (Replogle tube). Evaluate for associated conditions such as
VACTERL association (3 or more):
-Vertebral anomalies i.e. hemivertebrae, spina bifida
-Anal malformations i.e. imperforate anus
-Cardiac malformations i.e. VSD, ASD, Tetralogy Fallot
-Tracheo-Esophageal fistula (must be one of the associated conditions)
-Renal deformities i.e. absent kidney, hypospadia, etc.
-Limb dysplasia
Early surgical repair (transpleural or extrapleural) for those babies with no evidence
of pneumonia, adequate weight (>1200 gm) and no significant associated anomalies.
Babies with Chest-X-Ray positive findings, but adequate ABG's can also be primarily
repaired. Delayed repair (gastrostomy first) for all other patients. Surgical repair consist
of a 4th intercostal space right muscle-sparing thoracotomy (side of thoracotomy is
contralateral to side of aortic arch of patient), closure of tracheo-esophageal fistula and
primary esophago-esophagostomy. Esophagogram is done 7-10 days after repair.
Complications after surgery are: Anastomotic leak, anastomotic stricture,
gastroesophageal reflux, tracheomalacia, and recurrent TEF. The three most common
anastomotic complications are in order of frequency: stricture, leakage and recurrent TEF.
Recurrent TEF after surgical repair for esophageal atresia occurs in approximately 3-15%
of cases. Tension on the anastomoses followed by leakage may lead to local inflammation
with breakage of both suture lines enhancing the chance of recurrent TEF. Once
established, the fistula allows saliva and food into the trachea, hence clinical suspicion of
this diagnosis arises with recurrent respiratory symptoms associated with feedings after
repair of esophageal atresia. Diagnosis is confirmed with cineradiography of the
esophagus or bronchoscopy. A second thoracotomy is very hazardous, but has proved to
be the most effective method to close the recurrent TEF. Either a pleural or pericardial
flap will effectively isolate the suture line. Pericardial flap is easier to mobilize, provides
sufficient tissue to use and serves as template for ingrowth of new mucosa should leakage
occur. Other alternatives are endoscopic diathermy obliteration, laser coagulation, or
fibrin glue deposition.
B. Achalasia
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Achalasia in children is an uncommon esophageal motor disorder distinguished by
clinical, radiological and manometrics features. Incidence is estimated in 0.1 cases/year
per 100,000 populations under 14 years of age. Clinical presentation is characterized by
progressive dysphagia, regurgitation, weight loss, chest pain and nocturnal cough. Infants
exhibit failure to thrive. Diagnosis is established by barium swallow and confirmed by
manometry and motility studies. Barium swallows shows' esophageal dilatation, motility
alteration and a small caliber (bird-beak) cardio-esophageal junction. Manometry reveals
elevated E-G sphincter pressure, non- peristaltic esophageal contraction and failed
relaxation of lower esophageal sphincter upon swallowing. Videofluoroscopy can be of
help in the screening of esophageal motors disorders. Esophageal pneumatic balloon
dilatation is not an effective method of treatment in children due to the high rate of
recurrence of symptoms. Primary therapy is surgical (Heller's modified
esophagomyotomy), and results are similar after a transabdominal or thoracic approach.
Many authors favor a concomitant antireflux procedure in these patients. Nifedipine can
be of help as a short management in preparation for surgery. Long-term result presents'
a connection between achalasia and malignant disease of the esophagus .
To be continued,,,