Pediatric Anesthesia

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Pediatric Anesthesia

• Department of anesthesiology
• Cui Xiao Guang

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• The provision of safe anesthesia for pediatric
  patients depends on a clear understanding of the
  physiologic, pharmacologic, and psychological
  differences between children and adults.

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• Neonates 01 months
• Infants 112 months
• Toddlers 13 years
• small children 412 years

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DEVELOPMENTAL PHYSIOLOGY OF THE INFANT
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The pulmonary system 1

• The relatively large size of the infant's tongue
• The larynx is located higher in the neck
• The epiglottis is shaped differently, being short
  and stubby
• The vocal cords are angled
• The infant larynx is funnel shaped, the narrowest
  portion occurring at the cricoid cartilage
  uncuffed endotracheal tubes patients younger
  than 6 years.

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The pulmonary system 2

• Alveoli increase in number and size until the
  child is approximately 8 years old.
• Functional residural capacity (FRC) the same
  with adult induction and palinesthesia of
  anesthesia is rapid
• A-aDO2 is larger functional airway closure
• Limits oxygen reserves hypoxemia.
• The work of breathing (In premature infants)
• three times of adults,
• increased by cold stress or some degree
• of airway obstruction.
• RR two times of adults

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The pulmonary system 3

• Tidal volume(VT) is little physiological dead
  space is 30 of VT
• Airway resistance increasing secretion, upper
  airway infection
• Diaphragmatic and intercostal muscles do not
  achieve the adult configuration of type I muscle
  fibers until the child 2 years old apnea or
  carbon dioxide retention and respiratory failure.
• Infants have often been described as obligate
  nasal breathers lt5 months of age.

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The Cardiovascular System1

• In uterus foramen ovale, ductus arteriosus
  (right?left)
• At birth the fetal circulation becomes an
  adult-type circulation.-- transitional
  circulation
• Prolonged transitional circulation
• prematurity,
• infection,
• acidosis,
• pulmonary disease resulting in hypercarbia
  or hypoxemia (aspiration of meconium),
• hypothermia,
• congenital heart disease.

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The Cardiovascular System2

• The myocardial structure of the heart is less
  developed, produce less compliant ventricles
• This developmental myocardial immaturity
  sensitivity to volume loading,
• poor tolerance of increased afterload,
• heart rate-dependent cardiac output.

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The Cardiovascular System3

• Bradycardia and profound reductions in cardiac
  output
• activation of the parasympathetic nervous
  system
• hypoxia
• anesthetic overdose
• The sympathetic nervous system and baroreceptor
  reflexes are not fully mature.

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The Kidneys

• Renal function is markedly diminished in neonates
  and further diminished in preterm babies because
  of low perfusion pressure and immature glomerular
  and tubular function.
• Nearly complete maturation approximately 20
  weeks after birth
• Complete maturation about 2 years of age
• dehydration

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The Liver 1

• The functional maturity of the liver is somewhat
  incomplete.
• Most enzyme systems for drug metabolism are
  developed but not yet induced (stimulated) by the
  drugs that they metabolize.
• Jaundice decreased bilirubin breakdown

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The Liver 2

• A premature infant's liver has minimal glycogen
  stores and is unable to handle large protein
  loads
• hypoglycemia
• acidemia
• failure to gain weight when the diet
  contains too much protein.
• The lower the albumin value, the less protein
  binding and the greater the levels of free drug.

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The Gastrointestinal System

• At birth, gastric pH is alkalotic
• after birth the second day, pH is in the
  normal
• The ability to coordinate swallowing with
  respiration does not fully mature until the
  infant is 4 to 5 months of age gastroesophageal
  reflux
• If a developmental problem occurs within the
  gastrointestinal system, symptoms will occur
  within 24 to 36 hours of birth.
• Upper --vomiting and regurgitation
• Lower --abdominal distention and failure
  to pass meconium.

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Thermoregulation

• Thin skin, low fat content, and a higher surface
  relative to weight allow greater heat loss to the
  environment in neonates. ??
• Thermogenesis shivering and nonshivering
  (metabolism of brown fat).
• General anesthesia affects the metabolism of
  brown fat.--hypothermia
• Hypothermia delayed awakening from anesthesia,
  cardiac irritability, respiratory depression,
  increased pulmonary vascular resistance, and
  altered drug responses.

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Central nervous system

• More fat is in the central nervous system
• Permeability of Blood brain barrier is great
  opioiddecrement
• bilirubinkernicterus
• MAC?

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Pharmacological Differences

• The response to medications
• body composition,
• protein binding,
• body temperature,
• distribution of cardiac output,
• functional maturity of the heart,
• maturation of the blood-brain barrier,
• the relative size (as well as functional
  maturity) of the liver and kidneys,
• the presence or absence of congenital
  malformations

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Alterations in body composition have several
clinical implications for neonates

• a drug that is water soluble
• larger volume of distribution and larger
  initial dose (e.g., succinylcholine)
• less fat a drug that depends on redistribution
  into fat for termination of its action will have
  a longer clinical effect (e.g., thiopental)
• a drug that redistributes into muscle
• longer clinical effect (e.g., fentanyl)
• Others

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Inhaled Anesthetics

• Nitrous oxide
• Halothane
• Enflurane
• Isoflurane
• Sevoflurane
• Desflurane

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Nitrous oxide

• lower dissolubility ?????????
• neonate pneumothorax, emphysema
• congenital diaphragmatic hernia or
  acromphalus
• necrotic enteritis

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Enflurane

• In the introduction of anesthesia
  breathholding, cough, laryngospasm
• After anesthesia seizure-like activity

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Isoflurane

• Introduction of anesthesia and analepsia
  rapid
• respiratory depression, coughing, laryngospasm
• After extubate
• incidence of laryngospasmlt enflurane

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Sevoflurane

• induction is slightly more rapid
• anesthesia is steady
• respiratory tract irritation small
• the production of toxic metabolites as a result
  of interaction with the carbon dioxide absorbent
  must be considered .
• Introduction and short anesthesia sevoflurane
• Prolonged anesthesia elect other anesthetics

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Desflurane

• respiratory tract irritation strong
  laryngospasm (?50) during the gaseous
  induction of anesthesia
• Concern for the potential for carbon monoxide
  poisoning
• Hypertension and tachycardia

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Intravenous anesthetics

• Ketamine
• Thiopental
• Propofol
• Etomidate
• Benzodiazepines diazepam, midazolam
• Opioids morphine, fentanyl, alfentanil,
  sufentanil, remifentanil

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Ketamine 1

• Routes of administration
• intravenous 2 mg/kg
• intramuscular 5 to 10 mg/kg
• rectally 10 mg/kg
• orally 6 to 10 mg/kg
• intranasally 3 to 6 mg/kg

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Ketamine 2

• Undesirable side effects
• increased production of secretions
• vomiting
• postoperative "dreaming"
• hallucinations
• apnea
• laryngospasm
• increased intracranial pressure
• increased intraocular pressure

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Thiopental

• Intravenous 2.5 thiopental, 5 to 6 mg/kg
• Termination of effect occurs through
  redistribution of the drug into muscle and fat
• Thiopental should be used in reduced doses (2 to
  4 mg/kg) in children who have low fat stores,
  such as neonates or malnourished infants.

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Propofol

• Propofol is highly lipophilic and promptly
  distributes into and out of vessel-rich organs.
• Short duration rapid redistribution, hepatic
  glucuronidation, and high renal clearance.
• Dose 1-2 mg/kg
• higher in infants younger than 2
  years
• Pain lidocaine, ketamine

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Etomidate

• Pain, bucking.
• No commonly used

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Diazepam

• 0.1-0.3 mg/kg, orally provides
• may also be administered rectally
• has an extremely long half-life in neonates (80
  hours)
• Contraindicat until the infant is 6 months of
  age or until hepatic metabolic pathways have
  matured.

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Midazolam

• Midazolam is water soluble and therefore not
  usually painful on intravenous administration.
• Administration
• intravenous 0.05 to 0.08 mg/kg, maximum of
  0.8mg (weightlt10 kg)
• intramuscular 0.1 to 0.15 mg/kg, maximum
  of 7.5 mg
• oral 0.25 to 1.0 mg/kg, maximum of 20 mg
• rectal 0.75 to 1.0 mg/kg, maximum of 20 mg
  
• nasal 0.2 mg/kg
• sublingual 0.2 mg/kg

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Fentanyl

• Fentanyl
• rapid onset
• brief duration of action
• Dosage patient age, the surgical procedure, the
  health of the patient, and the use of anesthetic
  adjuvants.

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Alfentanil

• Eliminate more rapidly than fentanyl
• Pharmacokinetics independent of dose
• Margin of safety the greater the administered
  dose, the greater the elimination.
• Clearance of alfentanil may be increased in
  children in comparison to adults

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Sufentanil

• use primarily for cardiac anesthesia
• Children are able to clear sufentanil more
  rapidly than adults do.
• Bradycardia and asystole when a vagolytic drug
  was not administered simultaneously.

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Remifentanil

• Often use in pediatric anesthesia

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Muscle Relaxants

• Depolarizing Muscle Relaxant
• succinylcholine
• Nondepolarizing Muscle Relaxants
• Pancuronium, Vecuronium, Atracurium ,
  Pipecuronium, Rocuronium

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Succinylcholine

• the dose required for intravenous administration
  in infants (2.0 mg/kg) is approximately twice
  that for older patients
• Intravenous administration of atropine before
  the first dose of succinylcholine may reduce the
  incidence of arrhythmias

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Pancuronium

• useful for longer procedures
• no histamine is released
• The disadvantage tachycardia
• Administration 0.1 mg/kg

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Vecuronium

• Vecuronium is useful for shorter procedures in
  infants and children
• no histamine is released
• Administration 0.1mg/kg
• Duration 20 30min

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Atracurium

• Useful for shorter procedures in infants and
  children
• Particularly useful in newborns and patients with
  liver or renal disease. Why?
• Administration0.3 0.5 mg/kg
• Duration gt30 min

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Rocuronium

• Rocuronium has a clinical profile similar to that
  of vecuronium and atracurium
• Advantage can be administered intramuscularly

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Preoperative Preparation(1)

• The preoperative visit and preparation of the
  child for surgery are more important than the
  choice of premedication
• chart review, physical examination, and
  furnishing of information regarding the
  approximate time and length of surgery

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Preoperative Preparation(2)

• evaluates the medical condition of the child, the
  needs of the planned surgical procedure, and the
  psychological makeup of the patient and family
• explain in great detail what the child and family
  can expect and what will be done to ensure the
  utmost safety

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Fasting

• milk and solids before 6 hours
• clear fluids up to 2-3 hours before induction
• Infants who are breast-fed may have their last
  breast milk 4 hours before anesthetic induction

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Premedication (1)

• The need for premedication must be individualized
  according to the underlying medical conditions,
  the length of surgery, the desired induction of
  anesthesia, and the psychological makeup of the
  child and family

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Premeditation (2)

• A premedication is not normally necessary for the
  usual 6-month-old child but is warranted for a
  10- to 12-month-old who is afraid to be separated
  from parents
• Oral midazolam is the most commonly administered
  premedication.
• An oral dose of 0.25 to 0.33 mg/kg (maximum,
  20 mg)

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Premeditation (3)

• Premedications may be administered orally,
  intramuscularly, intravenously, rectally,
  sublingually, or nasally
• Although most of these routes are effective and
  reliable, each has drawbacks

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Merits and drawbacks

• Oral or sublingual not hurt but may have a
  slow onset or be spit out
• Intramuscular and Intravenous painful and may
  result in a sterile abscess
• Rectal make the patient feel uncomfortable
• Nasal irritating, although absorption is rapid

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Premeditation (4)

• Midrange doses of intramuscular ketamine (3 to 5
  mg/kg) combined with atropine (0.02 mg/kg) and
  midazolam (0.05 mg/kg) will result in a deeply
  sedated patient
• Higher doses of intramuscular ketamine (up to 10
  mg/kg) combined with atropine and midazolam may
  be administered to patients with anticipated
  difficult venous access to provide better
  conditions for insertion of the intravenous line

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Induction of Anesthesia

• The method of inducing anesthesia is determined
  by a number of factors
• ? the medical condition of the patient,
• ? the surgical procedure,
• ? the level of anxiety of the child,
• ? the ability to cooperate and communicate
  (because of age, developmental delay, language
  barrier),
• ? the presence or absence of a full
  stomach, and other factors

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Rectal Induction of Anesthesia

• Rectal administration of 10 methohexital
  reliably induces anesthesia within 8 to 10
  minutes in 85 of young children and toddlers
• The main advantage
• the child falls asleep in the parents arms,
• separates atraumatically from the parents.
• The main disadvantage drug absorption can be
  either markedly delayed or very rapid

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Intramuscular Induction of Anesthesia

• Many medications, such as ketamine (2 to 10 mg/kg
  combined with atropine and midazolam), or
  midazolam alone (0.15 to 0.2 mg/kg), are
  administered intramuscularly for premedication or
  induction of anesthesia
• The main advantage reliability
• the main disadvantage painful

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Intravenous Induction of Anesthesia

• Intravenous induction of anesthesia is the most
  reliable and rapid technique
• Intravenous induction may be preferable when
  induction by mask is contraindicated (e.g., in
  the presence of a full stomach)
• The main disadvantage painful and threatening
  for the child

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The Difficult Airway

• Difficult intubation
• maintain spontaneous respirations
• placing a stylet in the endotracheal
  tube
• fiberoptic brochoscope.

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The Child with Stridor (1)

• expiratory stridor
• intrathoracic airway obstruction ,
• . such as bronchiolitis, asthma, intrathoracic
  foreign body
• inspiratory stridor
• extrathoracic upper airway obstruction ,
• such as epiglottitis, laryngotracheobronchitis
  , laryngeal foreign body

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When a child has upper airway obstruction (as in
epiglottitis, laryngotracheobronchitis, and
extrathoracic foreign body) (shaded area) and
struggles to breathe against this obstruction,
dynamic collapse of the trachea increases
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The Child with Stridor (2)

• maintaining spontaneous respiration
• Induction of anesthesia with halothane or
  sevoflurane in oxygen by mask
• With the patient lightly anesthetized and after
  infiltration of local anesthetic, an intravenous
  line is inserted
• If stridor worsens or mild laryngospasm occurs,
  the pop-off valve is closed sufficiently to
  develop 10 to 15 cm H2 O of positive
  end-expiratory airway pressure.

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When a child has upper airway obstruction caused
by laryngospasm (A) or mechanical obstruction
(B), the application of approximately 10 cm H2 O
of positive end-expiratory pressure (PEEP) during
spontaneous breathing often relieves the
obstruction. That is, PEEP helps keep the vocal
cords apart (A) and the airway open (B, broken
lines)
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The Child with Stridor (3)

• A child with laryngotracheobronchitis or
  epiglottitis usually requires an uncuffed
  endotracheal tube that is 0.5 to 1.0 mm (internal
  diameter) smaller than normal
• total airway obstruction occur and mask
  ventilation or endotracheal intubation not be
  possible ----- tracheotomy

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The Child with a Full Stomach 1

• Children with a full stomach must be treated the
  same as adults with a full stomach
• child may be uncooperative and refuse to breathe
  oxygen before induction of anesthesia

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The Child with a Full Stomach 2

• enrich the environment with a high flow of oxygen
  
• Additional equipment
• two suction catheters ,
• two appropriately sized laryngoscopes
• While the child is breathing oxygen, atropine
  (0.02 mg/kg, up to 0.6 mg) may be administered
  intravenously
• cricoid cartilage

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Endotracheal Tubes

• For most children, the proper-size endotracheal
  tube and the proper distance of insertion
  relative to the alveolar ridge of the mandible or
  maxilla are moderately constant.

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• Tube diameter (in mm) age/44
• Infant 3 months to 1 year 10 cm
• Child 1 year 11 cm
• Child 2 year 12 cm
• Length of tube (in cm) age/212
• the tip of the endotracheal tube should pass
  only 12 cm beyond an infant's glottis.

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The Dedicated Pediatric Equipment

• Rendell-Baker-Soucek mask
• Ayres T tube
• Jackson Rees improved type of Ayres T tube have
  reservoir bag
• airflow 1000 ml 100 mlBW(kg) /min
• ( weightlt10kg)
• Laryngeal mask

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Epidural anesthesia
Epidural block procedures sacral intervertebral
approach (1), lumbar approach (i.e., midline
route) (2), and thoracic approach (i.e., midline
route) (3).
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Local Anesthetics

• 0.81.5 lidocaine
• 0.10.2 tetracaine
• 0.250.5 bupivacaine
• 0.250.5 ropivacaine

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Caudal anesthesia
Caudal block procedure. A, Insertion of the
needle at right angles to the skin in relation to
the coccyx (1) and the sacrococcygeal membrane
(2). B, Cephalad redirection of the needle after
piercing the sacrococcygeal membrane.
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Spinal anesthesia
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Axillary approaches
Axillary approaches to the brachial plexus
classic approach (A) and transcoracobrachialis
approach (B), indicating the pectoralis major
muscle (1), axillary artery (2), and
coracobrachialis muscle (3).
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Dose
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Monitoring

• The complexity of monitoring applied to pediatric
  patients must be consistent with the severity of
  the underlying medical condition and the planned
  surgical procedure.

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Routine Monitoring

• precordial stethoscope,
• ? esophageal stethoscope,
• blood pressure cuff,
• electrocardiogram,
• temperature probe,
• pulse oximeter,
• end-tidal carbon dioxide monitor

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Invasive Monitoring

• Arterial catheter
• Central venous catheter

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Intravenous Fluid

• the high metabolic demands
• the high ratio of body surface area to weight.

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The basis for calculating

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Other

• Fluid deficits,
• Third-space losses,
• Modifications because of hypothermia or
  hyperthermia,
• Requirements caused by unusual metabolic demands

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• 50 of the resulting deficit is replaced in the
  first hour and 25 in each of the next 2 hours.
• Loss with the surgical procedure
• from 1 mL/kg/hr for a minor surgical
  procedure to as much as 15 mL/kg/hr for major
  abdominal procedures.

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The composition of the intravenous fluid

• Child with greater hypoxic brain damage
• high blood glucose levels,
• recommend not using glucose-containing
  solutions routinely, especially for brief
  operative procedures
• All deficits and third-space losses
• A balanced salt solution (e.g., lactated
  Ringer's solution)
• Maintenance fluid
• 5 dextrose in 0.45 normal saline
• minimize the chance of hypoglycemia or
  accidental hyperglycemia

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General blood volume

• premature infant 100 to 120 mL/kg
• full-term infant 90 mL/kg
• child 3 to 12 months old 80 mL/kg
• child older than 1 year 70 mL/kg
• These are merely estimates of blood volume

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Simple formula
EBV(Starting hematocrit
Target hematocrit) MABL
Starting hematocrit
EBV estimated blood volume
Target hematocrit child younger than 3 months
--- gt35 child
older than 3 months --- 25-30

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Fluid replacememt and blood transfusion

• Blood loss lt1/3 MABL
• balanced solution
• balanced solutionvolume of blood loss 31
• Blood loss gt1/3 MABL
• colloid
• colloidvolume of blood loss 11
• Blood loss gt1MABL
• blood transfusion

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Volume of PRBCs

• (Desired
  Hct Present Hct)EBVBW (kg)
• Volume of PRBCs(ml)
• 
  Hematocrit of the PRBCs(60)

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Fresh Frozen Plasma

• PTgt15s or PTTgt 60s
• Fresh frozen plasma

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Platelets

• Thrombocytopenia lt15109/L
• idiopathic thrombocytopenic purpura,
  chemotherapy,
• infection,
• disseminated intravascular coagulopathy
• Dilution during massive blood loss
• lt50109/L

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Postoperative Management

• Extubate
• Laryngospasm
• Bradycardia
• Glossoptosis
• Postoperative analgesia
• gt9 years, PCA
• lt9 years, Nurse controlled analgesia(NCA)
• morphine, 20µg/kg/h, hypodermical
  injection or IM

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• Do not deck yourself up with fine clothew ,
• but enrich your mind with profound knowledge
• Thank you !