Co-ordinator:- Dr. Anshul Jain (M.D)
Speaker:- Dr. Sushil kr. patel
• The needs of infants and young children differ greatly from those of adults.
• Pediatric patients, especially neonates and infants younger than 6 months of
age, have anatomic and physiologic differences that place them at higher risk
of anesthetic complications than adults.
• Differences in responses to pharmacologic agents in this population further
add to the complexity of administering anesthesia to these patients. Many
diseases present exclusively or with greater frequency in this age group.
• A preterm infant is one born before 37 weeks gestation; a postmature infant is one
born after 42 weeks gestation.
• Any infant born at less than 2500 g is considered a low-birth-weight infant.
• Plotting weight against gestational age allows classification into three general
a) small for gestational age,
b) appropriate for gestational age
c) large for gestational age
• Infants who are small or large for gestational age often have developmental
problems or difficulties associated with maternal disease .
• Careful physical and neurologic examination at birth allows a fairly accurate
estimate of gestational age.
• The anesthesiologist should be aware of this type of evaluation so that potential
problems can be anticipated.
• Obtaining a perinatal history of problems during pregnancy (e.g., maternal drug
abuse, maternal infection, eclampsia, diabetes) or during and after delivery
(e.g., fetal distress, meconium aspiration, prematurity, postdelivery intubation) is
also valuable for assessing possible anesthetic implications that may require
specific considerations during and after anesthetic management.
Airway differences –Infant Vs Adult
Airway anatomy make the potential for technical airway difficulties greater in
infants than in teenagers or adults. The airway of infants differs in five ways:-
(1) the relatively large size of the infant's tongue in relation to the oropharynx
increases the likelihood of airway obstruction and technical difficulties during
(2) the larynx is located higher (more cephalic) in the neck, thus making straight
blades more useful than curved blades
(3) the epiglottis is shaped differently, being short, stubby, omega shaped, and
angled over the laryngeal inlet; control with the laryngoscope blade is therefore
(4) the vocal cords are angled, so a “blindly” passed endotracheal tube may easily
lodge in the anterior commissure rather than slide into the trachea
(5) the infant larynx is funnel shaped, the narrowest portion occurring at the cricoid
adult larynx is cylindrical and the infant larynx is funnel shaped
• In infants or young children, an endotracheal tube that easily passes the vocal
cords may be tight in the subglottic region because of the relatively greater
proportional narrowing at the level of the cricoid cartilage.
• for this reason that uncuffed endotracheal tubes have generally been
preferred for children younger than 6 years.
Airway differences –Infant Vs Adult
Big head , small body
Tongue/Epiglottis relatively larger
Glottis more superior, at level of C3 (vs C4 or 5)
Cricoid ring narrower than vocal cord aperture
• Compared with older children and adults, neonates and infants have less efficient
ventilation because of weak intercostal and diaphragmatic musculature (due to a
paucity of type I fibers), horizontal and more pliable ribs, and a protuberant
• Respiratory rate is elevated in neonates and gradually falls to adult levels by
• Tidal volume and dead space per kilogram remain constant during development.
• A relative paucity of small airways increases airway resistance. Alveolar maturation
is not complete until late childhood (about 8 years of age).
• Alveoli increase in number and size until the child is approximately 8 years old.
Further growth is manifested as an increase in size of the alveoli and airways.
• The work of breathing is increased and respiratory muscles easily fatigue. The small
and limited number of alveoli in neonates and infants reduces lung compliance; in
contrast, their cartilaginous rib cage makes their chest wall very compliant.
• The combination of these two characteristics promotes chest wall collapse during
inspiration and relatively low residual lung volumes at expiration. The resulting
decrease in functional residual capacity (FRC) is important because it limits oxygen
reserves during periods of apnea (eg, intubation) and readily predisposes neonates
and infants to atelectasis and hypoxemia.
• This may be exaggerated by their relatively higher rate of oxygen consumption.
• Hypoxic and hypercapnic ventilatory drives are not well developed in neonates and
infants. In fact, unlike in adults, hypoxia and hypercapnia depress respiration in
Developmental Changes of the Rib Cage
Reproduced from - R. S. Litman: Pediatric Anesthesia – The Requisites in Anesthesiology, Elsevier Mosby 2004
• Birth and the initiation of spontaneous ventilation initiate circulatory
changes, permitting neonates to survive in an extrauterine environment.
• Fetal circulation is characterized by high pulmonary vascular resistance, low
systemic vascular resistance (placenta), and right-to-left shunting of blood through
the foramen ovale and ductus arteriosus.
• The onset of spontaneous ventilation at birth is associated with decreased
pulmonary vascular resistance and increased pulmonary blood flow. As the left
atrial pressure increases, the foramen ovale functionally closes.
• Anatomic closure of the foramen ovale occurs between 3 months and 1 year of
age, although 20% to 30% of adults have probe-patent foramen ovales.
• Functional closure of the ductus arteriosus normally occurs 10 to 15 hours after
birth, with anatomic closure taking place in 4 to 6 weeks. Constriction of the ductus
arteriosus occurs in response to increased arterial oxygenation that develops after
• Ductus arteriosus may reopen during periods of arterial hypoxemia.
• During this critical period, the infant readily reverts from the adult circulation to a
fetal type of circulation; this state is called transitional circulation.
• Many factors (hypoxia, hypercapnia, anesthesia-induced changes in peripheral or
pulmonary vascular tone) can affect this precarious balance and result in a sudden
return to the fetal circulation. When such a “flip-flop” occurs, pulmonary artery
pressure increases to systemic levels, blood is shunted past the lungs via the patent
foramen ovale, and the ductus arteriosus may reopen and allow blood to shunt at
the ductal level
• Care must be directed to keeping the infant warm, maintaining normal arterial
oxygen and carbon dioxide tension, and minimizing anesthetic-induced myocardial
• The myocardial structure of the heart, particularly the volume of cellular mass
devoted to contractility, is significantly less developed in neonates than in adults.
• These differences, as well as developmental changes in contractile
proteins, produce a leftward displacement of the cardiac function curve and less
• This developmental immaturity of myocardial structures accounts for the
tendency toward biventricular failure, sensitivity to volume loading, poor
tolerance of increased afterload, and heart rate–dependent cardiac output.
• Another issue is that cardiac calcium stores are reduced because of immaturity of
the sarcoplasmic reticulum; consequently, neonates have a greater dependence
on exogenous (ionized) calcium and probably increased susceptibility to
myocardial depression by potent inhaled agents that have calcium channel
• Renal function is markedly diminished in neonates and further diminished
in preterm infants because of low perfusion pressure and immature
glomerular and tubular function .
• Nearly complete maturation of glomerular filtration and tubular function
occurs by approximately 20 weeks after birth, although it is somewhat
delayed in preterm infants. Complete maturation of renal function takes
place by about 2 years of age.
• Thus, the ability to handle free water and solute loads may be impaired in
neonates, and the half-life of medications excreted by means of
glomerular filtration will be prolonged .
• At term, the functional maturity of the liver is somewhat incomplete. Most enzyme
systems for drug metabolism are developed but not yet induced (stimulated) by the
agents that they metabolize.
• As the infant grows, the ability to metabolize medications increases rapidly for two
reasons: (1) hepatic blood flow increases and more drug is delivered to the
liver, and (2) the enzyme systems develop and are induced.
• The cytochrome P450 system is responsible for phase I drug metabolism of
lipophilic compounds. This system reaches approximately 50% of adult values at
birth, thus suggesting an overall reduced capacity for drug metabolism.
• However, this generalization does not hold true for all lipophilic medications, and
the ability of neonates to metabolize some drugs is dependent on specific
individual drug cytochromes. CYP3A is generally present at adult values at
birth, whereas other cytochromes are absent or reduced.
• Phase II reactions involve conjugation, which makes the drug more water soluble
to facilitate renal excretion. These reactions are often impaired in neonates and
result in jaundice (decreased bilirubin breakdown) and long drug half-lives
(e.g., morphine and benzodiazepines). Some of these reactions do not achieve
adult activity until after 1 year of age.
• A preterm infant's liver has minimal glycogen stores and is unable to handle large
protein loads. This difference accounts for the neonate's tendency toward
hypoglycemia and acidemia and for the failure to gain weight when the diet
contains too much protein.
• Additionally, plasma levels of albumin and other proteins necessary for binding of
drugs are lower in full-term newborns (and are even lower in preterm infants) than
in older infants .
• This condition has clinical implications regarding neonatal coagulopathy (e.g., the
need for vitamin K at birth), as well as for drug binding and pharmacodynamics, in
that the lower the albumin value, the less protein binding of some drugs with
resultant greater levels of unbound drug (unbound drug is the portion available to
cross biologic membranes).
• In addition, binding of some drugs to albumin may be altered in the presence of
hyperbilirubinemia in the neonatal period.
• At birth, gastric pH is alkalotic; by the second day of life, pH is in the normal
physiologic range for older children.
• The ability to coordinate swallowing with respiration does not fully mature until
infants are 4 to 5 months of age, thus resulting in a high incidence of
gastroesophageal reflux in newborns.
• This problem is particularly common in preterm infants.
• In general, if a developmental problem occurs within the gastrointestinal
system, symptoms will occur within 24 to 36 hours of life; upper intestinal
abnormalities are manifested as vomiting and regurgitation, whereas lower
intestinal abnormalities produce abdominal distention and failure to pass
• Infants are especially vulnerable to hypothermia because of the large ratio of
body surface area to weight, the thinness of the skin, and a limited ability to cope
with cold stress.
• Cold stress will result in increased oxygen consumption and can cause metabolic
acidosis. A preterm infant is more susceptible because of even thinner skin and
limited fat stores.
• The infant may compensate by means of shivering and nonshivering (cellular)
thermogenesis. The minimal ability to shiver during the first 3 months of life
makes cellular thermogenesis (metabolism of brown fat) the principal method of
• It is very important to address all aspects of possible heat loss during
anesthesia, as well as during transport to and from the operating room. Placing
the baby on a warming mattress and warming the operating room (80°F or
warmer) reduce heat lost by conduction.
• Keeping the infant in an incubator, covered with blankets, minimizes heat lost
through convection. The head should also be covered.
• Hot air blankets are the most effective means of warming children. Anesthetic
agents can alter many thermoregulatory mechanisms, particularly nonshivering
thermogenesis in neonates.
• Characteristics of fetal hemoglobin influence oxygen transport.
• fetal hemoglobin has a P50 (the partial pressure of oxygen at which hemoglobin is
50% saturated) of 19 mm Hg compared with 26 mm Hg for adults, which results in
a leftward shift of the fetal oxyhemoglobin dissociation curve.
• Subsequent increased affinity of hemoglobin for oxygen manifests as decreased
oxygen release to peripheral tissues. This decreased release is offset by increased
oxygen delivery provided by the increased hemoglobin concentrations
characteristic of neonates .
• By 2 to 3 months of age, however, physiologic anemia results. After 3
months, there are progressive increases in erythrocyte mass and hematocrit. By 4
to 6 months, the oxyhemoglobin dissociation curve approximates that of adults.
• In view of the decreased cardiovascular reserve of neonates and the leftward shift
of the oxyhemoglobin dissociation curve, it may be useful to maintain the
neonate's hematocrit closer to 40% than 30%, as is often accepted for older
• Calculation of the estimated erythrocyte mass and the acceptable erythrocyte loss
provides a useful guide for intraoperative blood replacement.
• The need for routine preoperative hemoglobin determinations is
• Routine preoperative hemoglobin determinations in children younger
than 1 year of age results in the detection of only a small number of
patients with hemoglobin concentrations less than 10 g/dL, and this rarely
influences management of anesthesia or delays planned surgery.
• Because of the potential benefit of identifying anemia during
infancy, routine preoperative hemoglobin testing may be justifiable only in
this age group.
Pharmacology and Pharmacodynamics
• The response of infants and children (and particularly neonates) to medications is
modified by many factors: 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, and the presence or absence of congenital
• The body compartments (fat, muscle, water) change with age .
• Total body water content is significantly higher in preterm than in term infants and
in term infants than in 2-year-olds. Fat and muscle content increases with age.
• These alterations in body composition have several clinical implications for
(1) A drug that is water soluble has a larger volume of distribution and usually
requires a larger initial dose (mg/kg) to achieve the desired blood level (e.g., most
(2) because there is less fat, a drug that depends on redistribution into fat for
termination of its action will have a longer clinical effect (e.g., thiopental); and
(3) drug that redistributes into muscle may have a longer clinical effect
(e.g., fentanyl, for which, however, saturation of muscle tissue has not been
In addition to these very basic concepts, other important factors play a role in the
neonate's response to medications:
(1) delayed excretion secondary to the larger volume of distribution
(2) immature hepatic and renal function, and
(3) altered drug excretion caused by lower protein binding. All of these factors lead to
clinically important neonatal patient-to-patient variability in pharmacokinetics and
• Older children tend to have mature renal and hepatic function, with normal adult
values for protein, fat, and muscle content. A greater proportion of cardiac output
is diverted to the liver and kidneys—which also weigh more in relation to body
mass—in older children than in infants.
• These factors usually mean that the half-life of most medications in children older
than 2 years is shorter than in adults or equivalent.
• In general, most medications will have a prolonged elimination half-life in preterm
and term infants, a shortened half-life in children older than 2 years up to the early
teen years, and a lengthening of half-life in those approaching adulthood.
• Children frequently present for surgery with evidence—a runny nose with
fever, cough, or sore throat—of a coincidental viral upper respiratory tract infection
• Attempts should be made to differentiate between an infectious cause of
rhinorrhea and an allergic or vasomotor cause.
• A viral infection within 2–4 weeks before general anesthesia and endotracheal
intubation appears to place the child at an increased risk for perioperative
pulmonary complications, such as wheezing (10-fold), laryngospasm (5-
fold), hypoxemia, and atelectasis. This is particularly likely if the child has a severe
cough, high fever, or a family history of reactive airway disease.
• The decision to anesthetize children with URTIs remains controversial and depends
on the presence of other coexisting illnesses, the severity of URTI symptoms, and
the urgency of the surgery.
• If surgery cannot be deferred, consideration should be given to an anticholinergic
premedication, mask ventilation, humidification of inspired gases, and a longer-
than-usual stay in the recovery room.
• The risk of perioperative complications is greatest in the presence of acute
infection but remains increased for 2-6 weeks after URTI.
• Airway reactivity is increased for up to 6-8 weeks following an URTI. Children
undergoing major surgery may have increased perioperative
complications, particularly infective complications.
• Most adverse perioperative events are easily manageable and have no lasting
• Induction of anaesthesia with an inhalation agent (sevoflurane, halothane) is
associated with more respiratory complications compared to induction with
propofol; induction with thiopentone is associated with the highest risk of
• . Respiratory complications are higher when neuromuscular blocking agents are
• Those with mild URTI have clear rhinorrhea, appear otherwise healthy, and have
clear lungs to auscultation and no fever. Overtly sick children have fever
>38°C, purulent nasal discharge, productive cough and are ill-appearing with signs
of pulmonary involvement.
• Most children with mild URTI can be safely anaesthetized without significant
morbidity and those children with more severe symptoms should have elective
surgeries postponed for at least 4 weeks.
• Few, if any, preoperative laboratory results have been deemed cost effective.
Some pediatric centers require no preoperative laboratory tests in healthy
children undergoing minor procedures.
• this places more responsibility on the anesthesiologist, surgeon, and pediatrician
to correctly identify those patients who should have preoperative testing for
specific surgical procedures.
• Most asymptomatic patients with murmurs do not have significant cardiac
• Innocent murmurs may occur in more than 30% of normal children.
• They are usually soft, short systolic ejection murmurs that are best heard along
the left upper or left lower sternal border without significant radiation.
• Innocent murmurs at the left upper sternal border are due to flow across the
pulmonic valve (pulmonic ejection) whereas those at the lower left border are
due to flow from the left ventricle to the aorta (Still's vibratory murmur).
• An echocardiogram should be obtained if the patient is symptomatic (eg, poor
feeding, failure to thrive, or easy fatigability); the murmur is
harsh, loud, holosystolic, diastolic, or radiates widely; or pulses are either
bounding or markedly diminished
• Clear liquids –2 hours
• Breast milk –4 hours
• Formula or milk –6 hours
• Light meal –6-7 hours
• Full meal –8 hours
• Monitoring requirements for infants and children are generally similar to adults
with some minor modifications.
• Noninvasive blood pressure monitors have proved to very reliable.
• A precordial stethoscope provides an inexpensive means of monitoring heart
rate, quality of heart sounds, and airway patency.
• Small pediatric patients have a smaller allowable margin of error. Pulse oximetry
and capnography assume an even greater monitoring role in pediatric patients
because hypoxia from inadequate ventilation is a major cause of perioperative
morbidity and mortality.
• In neonates, the pulse oximeter probe should preferably be placed on the right
hand or earlobe to measure preductal oxygen saturation.
• End-tidal CO2 analysis allows assessment of the adequacy of
ventilation, confirmation of endotracheal tube placement, and early warning of
malignant hyperthermia. Nonetheless, the small tidal volumes and rapid
respiratory rates of small infants can present difficulties with some capnograph
• Flow-through (mainstream) analyzers are usually less accurate in patients weighing
less than 10 kg. Even with aspiration (sidestream) capnographs, the inspired
(baseline) CO2 can appear falsely elevated and the expired (peak) CO2 can be falsely
• The degree of error depends on many factors but can be minimized by placing the
sampling site as close as possible to the tip of the endotracheal tube, using a short
length of sampling line, and lowering gas-sampling flow rates (100–150 mL/min).
• Temperature must be closely monitored in pediatric patients because of a higher
risk for malignant hyperthermia and the potential for both iatrogenic hypothermia
• Hypothermia can be prevented by maintaining a warm operating room
environment (26°C or higher), warming and humidifying inspired gases, using a
warming blanket and warming lights, and warming all intravenous fluids.
• Invasive monitoring (eg, arterial cannulation, central venous catheterization)
requires considerable expertise and extreme caution.
• All air bubbles should be removed from pressure tubing and only small volume
flushes should be used to prevent air embolism, inadvertent heparinization, and
• Urinary output is an important measure of volume status.
• Neonates who are premature or small for gestational age, who have received
hyperalimentation, or whose mothers are diabetic may be prone to hypoglycemia.
• These infants should have frequent serum glucose determinations: levels < 30
mg/dL in the neonate and < 40 mg/dL in older children indicate hypoglycemia.
• 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. Premedication is not normally
necessary for the usual 6-month-old infant 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) generally results in a very compliant child
who will separate from parents without crying.
• Premedications may also be administered
intramuscularly, intravenously, rectally, sublingually, or nasally. Although most of
these routes are effective and reliable, each has drawbacks.
• Oral or sublingual premedication does not hurt but may have a slow onset or be
spit out; drug taste and child cooperation are the main determinants of success.
• Intramuscular medications hurt and may result in a sterile abscess. Intravenous
medications may be painful during injection or at the start of infusion. Rectal
medications sometimes make the child feel uncomfortable, cause defecation, and
• Nasal medications can be irritating, although absorption is rapid.
• Midrange doses of intramuscular ketamine (2 to 4 mg/kg) combined with
atropine (0.02 mg/kg) and midazolam (0.05 mg/kg), or oral ketamine (4 to
6 mg/kg) combined with atropine (0.02 mg/kg) and midazolam
(0.5 mg/kg, maximum of 20 mg), will result in a deeply sedated child
• This combination is generally reserved for children who refuse oral premedication
or those in whom lighter premedication regimens have failed in the past. Higher
doses of intramuscular ketamine (up to 10 mg/kg) combined with atropine and
midazolam may be administered to children with anticipated difficult venous
access or in whom an intravenous line is necessary for induction (e.g., infants
with congenital heart disease) to provide better conditions for insertion of an
• Anticholinergic drugs are not routinely administered intramuscularly to children
because they are painful on administration and do not significantly reduce
laryngeal reflexes during induction of anesthesia.
• On the other hand, atropine (0.02 mg/kg) administered orally or intramuscularly
less than 45 minutes before induction does reduce the incidence of hypotension
during induction with potent inhaled anesthetics, but only in infants younger
than 6 months.
• Neonates, infants, and young children have relatively higher alveolar ventilation
and lower FRC compared with older children and adults.
• This higher minute ventilation-to-FRC ratio with relatively higher blood flow to
vessel-rich organs contributes to a rapid rise in alveolar anesthetic concentration
and speeds inhalation induction.
• Furthermore, the blood/gas coefficients of volatile anesthetics are lower in
neonates than in adults, resulting in even faster induction times and potentially
increasing the risk of overdosing.
• The minimum alveolar concentration (MAC) for halogenated agents is higher in
infants than in neonates and adults .
• Unlike other agents, sevoflurane has the same MAC in neonates and infants. For
unknown reasons, use of nitrous oxide in children does not augment the effects
(lower MAC requirements) of desflurane and to some extent sevoflurane as it does
for other agents.
• The blood pressure of neonates and infants tends to be more sensitive to volatile
anesthetics, probably because of not fully developed compensatory mechanisms
(eg, vasoconstriction, tachycardia) and an immature myocardium that is very
sensitive to myocardial depressants.
• As with adults, halothane also sensitizes the heart to catecholamines; the
maximum recommended dose of epinephrine in local anesthetic solutions during
halothane anesthesia is 10 micro g/kg.
• Cardiovascular depression, bradycardia, and arrhythmias are significantly less with
sevoflurane than with halothane.
• Halothane and sevoflurane are least likely to irritate the airway and cause breath
holding or laryngospasm during induction .
• Volatile anesthetics appear to depress ventilation more in infants than in older
children. Sevoflurane is associated with the least respiratory depression.
Prepubertal children are at much less risk for halothane-induced hepatic
dysfunction than adults.
• Overall, sevoflurane appears to have a greater therapeutic index than halothane
and has become a preferred induction agent in pediatric anesthesia.
• The rate of emergence is fastest following desflurane and sevoflurane
anesthesia, but both agents are associated with an increased incidence of
agitation or delirium upon emergence, particularly in young children.
• Because of the these, many clinicians switch to either isoflurane or
halothane for maintenance anesthesia following a sevoflurane induction .
• speed of emergence from halothane and isoflurane anesthesia appears to
be similar for procedures lasting less than 1 h.
• Based on weight, infants and young children require larger doses of propofol
because of a larger volume of distribution compared to adults. Children also have a
shorter elimination half-life and higher plasma clearance for propofol.
• Whereas recovery from a single bolus is not appreciably different from
adults, recovery following a continuous infusion may be more rapid. For the same
reasons, children may require higher rates of infusion for maintenance of
anesthesia (up to 250micro g/kg/min)
• Propofol is not recommended for sedation of critically ill pediatric patients in the
intensive care unit (ICU). The drug has been associated with higher mortality
compared to other agents, and a controversial "propofol infusion syndrome" has
• Its essential features are metabolic acidosis, hemodynamic
instability, hepatomegaly, rhabdomyolysis, and multiorgan failure. Although
appearing primarily in critically ill children, this rare syndrome has been reported in
adults and in patients undergoing long-term propofol infusion (> 48 h) for sedation
at high doses (> 5 mg/kg/h.
• Children require relatively higher doses of thiopental compared to adults. The
elimination half-life is shorter and the plasma clearance is greater than in adults.
• In contrast, neonates, particularly those depressed at birth, appear to be more
sensitive to barbiturates and have less protein binding, a longer half-life, and
impaired clearance. The thiopental induction dose for neonates is 3–4 mg/kg
compared to 5–6 mg/kg for infants.
Nonvolatile Anesthetics conti......
Opioids appear to be more potent in neonates than in older children and adults.
Possible explanations include easier entry across the blood–brain
barrier, decreased metabolic capability, or increased sensitivity of the respiratory
Morphine sulfate should be used with caution in neonates because hepatic
conjugation is reduced and renal clearance of morphine metabolites is decreased.
• The cytochrome P-450 pathways mature at the end of the neonatal period. Older
pediatric patients have relatively high rates of biotransformation and elimination as
a result of high hepatic blood flow.
Sufentanil, alfentanil, and, possibly, fentanyl clearances may be higher in children than
in adults. Remifentanil clearance is increased in neonates and infants but
elimination half-life is unaltered compared to adults.
Neonates and infants may be more resistant to the hypnotic effects of
ketamine, requiring slightly higher doses than adults; pharmacokinetics do not
appear to be significantly different from adults.
• The combination of ketamine and fentanyl is more likely to cause hypotension in
neonates and young infants than ketamine and midazolam. Etomidate has not been
studied adequately in pediatric patients less than 10 years old; its profile in older
children is similar to adults.
Midazolam has the fastest clearance of all the benzodiazepines; however, midazolam
clearance is significantly less in neonates than in older children. Moreover, the
combination of midazolam and fentanyl can cause profound hypotension
• All muscle relaxants generally have a shorter onset (up to 50% less) in pediatric
patients because of shorter circulation times than adults.
• Intravenous succinylcholine (1–1.5 mg/kg) has the fastest onset. Infants require
significantly higher doses of succinylcholine (2–3 mg/kg) than older children and
adults because of the relatively larger volume of distribution (extracellular space).
This discrepancy disappears if dosage is based on body surface area.
• With the notable exclusion of succinylcholine, mivacurium, and possibly
cisatracurium, infants require significantly less muscle relaxant than older children.
The response of neonates to nondepolarizing muscle relaxants is quite variable.
Immaturity of the neuromuscular junction (particularly in premature neonates)
tends to increase sensitivity, whereas a disproportionately large extracellular
compartment dilutes drug concentration.
• The relative immaturity of neonatal hepatic function prolongs the duration of
action for drugs that depend primarily on hepatic metabolism
(eg, pancuronium, vecuronium, and rocuronium).
• In contrast, atracurium and cisatracurium, which do not depend on hepatic
biotransformation, reliably behave as intermediate acting muscle relaxants.
Breakdown of mivacurium also does not appear to be significantly altered in
• Children are more susceptible than adults to cardiac
arrhythmias, hyperkalemia, rhabdomyolysis, myoglobinemia, masseter spasm, and
malignant hyperthermia after administration of succinylcholine. If a child
unexpectedly experiences cardiac arrest following administration of
succinylcholine, immediate treatment for hyperkalemia should be instituted.
• For this reason, succinylcholine is best avoided for routine elective surgery in
children and adolescents. Unlike in adult patients, profound bradycardia and sinus
node arrest can develop in pediatric patients following the first dose of
succinylcholine without atropine pretreatment. Atropine (0.1 mg minimum) must
therefore always be administered prior to succinylcholine in children.
• Generally accepted indications for succinylcholine in children are rapid sequence
induction with a full stomach, laryngospasm. Intramuscular succinylcholine (4–6
mg/kg) can be used for the latter; in this situation, atropine (0.02 mg/kg
intramuscularly) should be administered at the same time to prevent bradycardia.
• Some clinicians advocate intralingual administration (2 mg/kg in the mid-line to
avoid hematoma formation) as an emergency alternate route.
• Some clinicians consider rocuronium (0.6 mg/kg) to be the drug of choice for
routine intubation in pediatric patients with intravenous access because it has the
fastest onset of nondepolarizing neuromuscular blocking agents .
Higher doses of rocuronium (0.9–1.2 mg/kg) may be used for rapid sequence induction
but a prolonged duration (up to 90 min) should be expected. Rocuronium is the
only nondepolarizing neuromuscular blocker that can be given intramuscularly
(1.0–1.5 mg/kg) but requires 3–4 min for onset.
• Mivacurium, atracurium, or cisatracurium may be preferred agents in young
infants, particularly for short procedures, because these three drugs consistently
display short to intermediate duration. Mivacurium is typically used for procedures
lasting 10–15 min, whereas atracurium or cisatracurium is usually used for
procedures lasting more than 30 min.
• Because of the extreme variability in response, the doses of long-acting muscle
relaxants used for infants should be titrated carefully, starting with one third to
one half of the usual dose administered to older children.
Antagonism of neuromuscular blockade in all neonates and small infants, even if they
have recovered clinically, because any increase in the work of breathing may cause
fatigue and respiratory failure. Useful signs of reversal are the ability to lift the legs
and arms and recovery of the train-of-four response to peripheral nerve
• reversed with neostigmine (0.03–0.07 mg/kg) or edrophonium (0.5–1 mg/kg)
along with an anticholinergic agent (glycopyrrolate 0.01 mg/kg or atropine 0.01–
Emergence & Recovery
Pediatric patients are particularly vulnerable to two postanesthetic complications: laryngospasm
and postintubation croup.
Laryngospasm is a forceful, involuntary spasm of the laryngeal musculature caused by
stimulation of the superior laryngeal nerve .
• It may occur at induction, emergence, or any time in between without an endotracheal
tube. Laryngospasm is more common in young pediatric patients (almost 1 in 50) than in
adults, being highest in infants 1–3 months old.
• Laryngospasm at the end of a procedure can usually be avoided by extubating the patient
either awake (opening the eyes) or while deeply anesthetized (spontaneously breathing but
not swallowing or coughing); both techniques have advocates.
• Extubation during the interval between these extremes, however, is generally recognized as
hazardous. A recent URTI predisposes patients to laryngospasm on emergence.
Treatment of laryngospasm includes gentle positive- pressure ventilation, forward jaw
thrust, intravenous lidocaine (1–1.5 mg/kg), or paralysis with intravenous succinylcholine
(0.5–1 mg/kg) or rocuronium (0.4 mg/kg) and controlled ventilation.
• Intramuscular succinylcholine (4–6 mg/kg) remains an acceptable alternative in patients
without intravenous access and in whom more conservative measures have failed.
• Laryngospasm is usually an immediate postoperative event but may occur in the recovery
room as the patient wakes up and chokes on pharyngeal secretions.
• For this reason, recovering pediatric patients should be positioned in the lateral position so
that oral secretions pool and drain away from the vocal cords.
• Croup is due to glottic or tracheal edema. Because the narrowest part of the
pediatric airway is the cricoid cartilage, this is the most susceptible area.
• Croup is less common with endotracheal tubes that are uncuffed and small enough
to allow a slight gas leak at 10–25 cm H2O.
• Postintubation croup is associated with early childhood (age 1–4 years), repeated
intubation attempts, large endotracheal tubes, prolonged surgery, head and neck
procedures, and excessive movement of the tube (eg, coughing with the tube in
place, moving the patient's head).
• Intravenous dexamethasone (0.25–0.5 mg/kg) may prevent formation of
edema, and inhalation of nebulized racemic epinephrine (0.25–0.5 mL of a 2.25%
solution in 2.5 mL normal saline) is an effective treatment.
• Although postintubation croup is a complication that occurs later than
laryngospasm, it almost always appears within 3 h after extubation.
• The primary uses of regional techniques in pediatric anesthesia have been to
supplement and lower general anesthetic requirements and provide good
postoperative pain relief.
• Caudal blocks have proved useful in a variety of surgeries, including
circumcision, inguinal herniorrhaphy, hypospadias repair, anal surgery, clubfoot
repair, and other subumbilical procedures.
• Contraindications include infection around the sacral hiatus, coagulopathy, or
anatomic abnormalities. The patient is usually lightly anesthetized or sedated and
placed in the lateral position.
• For pediatric caudal anesthesia, a short bevel 22-gauge needle can be used.
• Loss of resistance should be assessed with saline, not air, because of the latter's
possible association with hemodynamically significant air embolism.
• After the characteristic "pop" that signals penetration of the sacrococcygeal
membrane, the needle is lowered and advanced only a few more millimeters to
avoid entering the dural sac or the anterior body of the sacrum.
• Aspiration is used to check for blood or cerebrospinal fluid; local anesthetic can
then be slowly injected; a 2-mL test dose of local anesthetic with epinephrine
(1:200,000) helps exclude intravascular placement.
Regional Anesthesia conti....
• Many anesthetic agents have been used for caudal anesthesia in pediatric
patients, with 1% lidocaine (up to 7 mg/kg for an epinephrine-containing solution)
and 0.125–0.25% bupivacaine (up to 2.5 mg/kg) being most common.
• Ropivacaine 0.2% (up to 2 mg/kg) can provide analgesia similar to bupivacaine but
with less motor blockade.
• The volume of local anesthetic required depends on the level of blockade
desired, ranging from 0.5 mL/kg for a sacral block to 1.25 mL/kg for a midthoracic
block. Single-shot injections generally last 4–12 h.
• Placement of 20-gauge caudal catheters with continuous infusion of local
anesthetic (eg, 0.125% bupivacaine or 0.1% ropivacaine at 0.2–0.4 mg/kg/h) or an
opioid (eg, fentanyl 2micro g/mL at 0.6micro g/kg/h) allows prolonged anesthesia
and postoperative analgesia.
• Complications are rare but include local anesthetic toxicity from prolonged
continuous infusions or intravascular injection
(eg, seizures, hypotension, dysrhythmias), spinal blockade, and respiratory
• Postoperative urinary retention does not appear to be a problem following single-
dose caudal anesthesia.
Perioperative Fluid Requirements
• Meticulous fluid management is required in small pediatric patients because of
extremely limited margins of error.
• A programmable infusion pump or a buret with a microdrip chamber should be
used for accurate measurements.
• Drugs are flushed through low dead-space tubing to minimize unnecessary fluid
• Fluid overload is diagnosed by prominent veins, flushed skin, increased blood
pressure, decreased serum sodium, and a loss of the folds in the upper eyelids.
Fluid therapy can be divided into maintenance, deficit, and replacement
1)Maintenance Fluid Requirements- Maintenance requirements for pediatric
patients can be determined by the formula , 4:2:1 rule: 4 mL/kg/h for the first 10
kg of weight, 2 mL/kg/h for the second 10 kg, and 1 mL/kg/h for each remaining
kilogram. The choice of maintenance fluid remains controversial.
• A solution such as D5½NS with 20 mEq/L of potassium chloride provides adequate
dextrose and electrolytes at these maintenance infusion rates.
• D51/4NS may be a better choice in neonates because of their limited ability to
handle sodium loads. Neonates require 3–5 mg/kg/min of a glucose infusion to
maintain euglycemia (40–125 mg/dL); premature neonates require 5–6
2)Deficits-In addition to a maintenance infusion, any preoperative fluid deficits must
be replaced as rule 4:2:1
• In contrast to adults, infants respond to dehydration with decreased blood
pressure but without increased heart rate.
• Preoperative fluid deficits are typically administered with hourly maintenance
requirements as 50% in the first hour and 25% in the second and third hours.
• Large quantities of dextrose-containing solutions are avoided to prevent
hyperglycemia. Preoperative fluid deficits are usually replaced with a balanced salt
solution (eg, lactated Ringer's ) or ½ normal saline. Compared with lactated
Ringer's injection, normal saline has the disadvantage of promoting hyperchloremic
• If a child is thought to be at risk for hypoglycemia, 5% dextrose in 0.45% normal
saline should be administered by “piggyback” infusion at maintenance rates. This
minimizes the chance of a bolus administration of glucose and satisfies the concern
for unrecognized hypoglycemia or accidental hyperglycemia.
• For most children, lactated Ringer's solution is the only fluid required.
3)Replacement Requirements- Replacement can be subdivided into blood loss
and third-space loss.
Blood Loss-The blood volume of premature neonates (100 mL/kg), full-term neonates
(85–90 mL/kg), and infants (80 mL/kg) is proportionately higher than that of adults
• An initial hematocrit of 55% in the healthy full-term neonate gradually falls to as
low as 30% in the 3-month-old infant before rising to 35% by 6 months.
• Hemoglobin (Hb) type is also changing during this period: from a 75%
concentration of HbF (high oxygen affinity, low PaO2, poor tissue unloading) at birth
to almost 100% HbA (low oxygen affinity, high PaO2, good tissue unloading) by 6
• Blood loss is typically replaced with non-glucose-containing crystalloid (eg, 3 mL of
lactated Ringer's injection for each milliliter of blood lost) or colloid solutions
(eg, 1 mL of 5% albumin for each milliliter of blood lost) until the patient's
hematocrit reaches a predetermined lower limit.
• In premature and sick neonates, this may be as high as 40% or 50%, whereas in
healthy older children a hematocrit of 20–26% is generally well tolerated.
• Because of their small intravascular volume, neonates and infants are at an
increased risk for electrolyte disturbances (eg, hyperglycemia, hyperkalemia, and
hypocalcemia) that can accompany rapid blood transfusion.
• Platelets and fresh frozen plasma 10–15 mL/kg should be given when blood loss
exceeds 1–2 blood volumes. One unit of platelets per 10 kg weight raises the
platelet count by about 50,000/L. The pediatric dose of cryoprecipitate is 1 U/10 kg
Third-Space Loss- These losses are impossible to measure and must be estimated by
the extent of the surgical procedure. One popular guideline is 0–2 mL/kg/h for
relatively atraumatic surgery (eg, strabismus correction) and up to 6–10 mL/kg/h
for traumatic procedures (eg, abdominal abscess). Third-space loss is usually
replaced with lactated Ringer's .
• Hypotension is a late finding in pediatric patients (children may maintain a
normal blood pressure until 35% of blood volume is lost).
• Tachycardia is sensitive but not specific indicator.
• Prolonged capillary refill (> 2 seconds), especially when combined with
tachycardia, is more specific, although it may be difficult to measure.
• Cold skin and decreased urine output may be present. Weak
pulses, mottling, cyanosis, and impaired consciousness may all precede
hypotension. In fact, hypotension is an ominous sign in pediatric patients
medical status mortality
ASA I normal healthy patient without organic, biochemical,
or psychiatric disease
ASA II mild systemic disease with no significant impact on
daily activity e.g. mild diabetes, controlled
hypertension, obesity .
Unlikely to have
ASA III severe systemic disease that limits activity e.g. angina,
COPD, prior myocardial infarction
ASA IV an incapacitating disease that is a constant threat to
life e.g. CHF, unstable angina, renal failure ,acute MI,
respiratory failure requiring mechanical ventilation
ASA V moribund patient not expected to survive 24 hours e.g.
ASA VI brain-dead patient whose organs are being harvested
ASA Physical Status Classification System
For emergent operations, you have to add the letter ‘E’ after the classification.