Pediatric Flashcards
1
Q
How does the oxygen consumption of a neonate compare with that of an adult?
A
- The oxygen consumption of a neonate is about twice that of an adult. In neonates
the oxygen consumption increases from 5 mL/kg per minute at birth to about
7 mL/kg per minute at 10 days of life and 8 mL/kg per minute at 4 weeks of
life. Oxygen consumption gradually declines over the subsequent months.
2
Q
- How does the cardiac output of a neonate compare with that of an adult?
A
- The cardiac output of a neonate is 30% to 60% higher than that of adults. This helps
to meet the increase in oxygen demand neonates have as compared with
adults.
3
Q
- Are changes in the cardiac output of a neonate more dependent on changes in the
heart rate or stroke volume?
A
- Changes in the cardiac output of a neonate or infant are dependent on changes
in the heart rate, because stroke volume is relatively fixed by the lack of
distensibility of the left ventricle in this age group. The neonate’s myocardium
depends heavily on the concentration of ionized calcium, such that hypocalcemia
can significantly depress myocardial function.
4
Q
- How does the position of the oxyhemoglobin dissociation curve in a neonate
compare with that of an adult? Describe how this affects the affinity of oxygen for
hemoglobin. At what age does the curve approximate that of an adult?
A
- In neonates, the oxyhemoglobin dissociation curve is shifted to the left. This
reflects a P50 lower than 26 mm Hg, meaning that less of a PaO2 is required for a
50% saturation of hemoglobin. Conversely, the oxygen is more tightly bound to
hemoglobin in neonates, necessitating a lower PaO2 for release of oxygen to the
tissues. This occurs as a result of fetal hemoglobin. The position of the
oxyhemoglobin dissociation curve becomes equal to that of adults by 4 to 6
months of age
5
Q
- How does the hemoglobin level of a neonate compare with that of an adult? How
does the hemoglobin level change as the infant progresses to 2 years old?
A
- The hemoglobin level of a neonate is approximately 17 g/dL. This, along with the
increase in cardiac output, helps to offset the increase in oxygen requirements
characteristic of neonates. At 2 to 3 months of age the hemoglobin of infants
decreases to about 11 g/dL during the time period when fetal hemoglobin is being
replaced by adult hemoglobin. This is termed the physiologic anemia of infancy,
which may persist for a few months. During the remainder of the first year of
life the hemoglobin level gradually increases and continues to do so until puberty,
when hemoglobin levels approach adult hemoglobin levels
6
Q
- What hemoglobin level is worrisome in the newborn? What hemoglobin level is
worrisome in infants older than 6 months of age?
A
- A hemoglobin level of 13 g/dL or less is worrisome in the newborn. In infants older
than 6 months of age, a hemoglobin level less than 10 g/dL is worrisome.
7
Q
- At what age does the foramen ovale close? What percent of adults have a probe
patent foramen ovale?
A
- The foramen ovale closes between 3 and 12 months of age. Twenty to thirty percent
of adults have a probe patent foramen ovale
8
Q
- How well do neonates reflexively respond to hemorrhage as compared with adults?
A
- Because of the decreased ability of neonates to vasoconstrict in response to
hypovolemia, neonates are less able to tolerate hemorrhage with vasoconstrictive
responses
9
Q
- How does alveolar ventilation in neonates compare with that of adults?
A
- Alveolar ventilation in neonates is 4 to 5 times higher than that of adults.
10
Q
- How does the tidal volume per weight in neonates compare with that of adults?
A
- Tidal volume per weight in neonates is similar to that of adults.
11
Q
- How does the respiratory rate in neonates compare with that of adults?
A
- The respiratory rate in neonates is three to four times higher than that of adults.
12
Q
- How does carbon dioxide production in neonates compare with that of adults?
How does the PaCO2 in neonates compare with that of adults?
A
- Carbon dioxide production in neonates is higher than that of adults. The PaCO2
in neonates is similar to that of adults, despite the increase in production.
This is due to the increase in alveolar ventilation in neonates when compared with
adults. (
13
Q
- How does the PaO2 change in the first few days of life?
A
- The PaO2 in the first few days after birth increases rapidly. The initially low PaO2 is due
to a decrease in the functional residual capacity and to the perfusion of alveoli
filled with fluid. The functional residual capacity of neonates increases over the first
few days of life until it reaches adult levels at about 4 days of age
14
Q
- How predictable is the neonate’s response to hypoxia?
A
- The neonate’s response to hypoxia is somewhat unpredictable, owing to the
immaturity of the central nervous system’s regulatory centers for ventilation in
this age group. Neonates have decreased ventilatory responses to hypoxemia and
hypercarbia.
15
Q
- What percent body weight in neonates is contributed by the extracellular fluid
volume? How does this compare with an adult?
A
- Extracellular fluid volume accounts for approximately 40% of the body weight of
the neonate at birth. This compares with approximately 20% of body weight in
adults being accounted for by extracellular fluid volume. The proportion of
extracellular fluid volume to body weight in neonates approaches the adult
proportion by 18 to 24 months of age.
16
Q
- What are some ways in which infants and children maintain normal body
temperature? Why is maintenance of normal body temperature more difficult in
neonates and children than in an adult?
A
- Some ways in which infants and children maintain normal body temperature
include the metabolism of brown fat, crying, and vigorous movements. The
metabolism of brown fat is stimulated by circulating norepinephrine. Children and
infants, unlike adults, do not shiver to maintain their body temperature.
Maintenance of normal body temperature is more difficult in neonates and infants
than in adults because of their larger body surface area-to-volume ratio, as well
as the relative lack of fat for insulation. (556)
17
Q
- How effective is kidney function at birth? When does kidney function become
approximately equivalent to that of an adult?
A
- Kidney function at birth is immature. There is a decreased glomerular filtration
rate, decreased sodium excretion, and decreased concentrating ability relative
to that of an adult. Kidney function progressively matures over the first 2 years of
life. Initially, in the first 3 months of life, kidney function increases rapidly to
double or triple the glomerular filtration rate possible at birth. Kidney function
then matures more slowly from 3 months to 24 months, when adult levels of
kidney function are reached
18
Q
- After fluid restriction, what is the maximum urine osmolarity possible for term
neonates at birth? At what age are adult levels of urine concentrating abilities
achieved?
A
- After fluid restriction, the term neonate at birth can only concentrate urine to
a maximum osmolarity of about 525 mOsm/kg. After 15 to 30 days of age,
neonates are able to concentrate their urine to a maximum osmolarity of about
950 mOsm/kg. Adult levels of urine concentrating ability are achieved by 6 to
12 months of age. (550)
19
Q
- What are some physiologic characteristics of neonates that explain the
pharmacologic differences between pediatric and adult responses to drugs?
A
- Some physiologic characteristics of neonates that explain the pharmacologic
differences between pediatric and adult responses to drugs include an increased
extracellular fluid volume, increased metabolic rate, decreased renal function,
and decreased receptor maturity
20
Q
- How is the uptake and distribution of inhaled anesthetics different in neonates and
infants when compared with adults?
A
- The uptake and distribution of inhaled anesthetics is more rapid in neonates than
in adults. This is most likely due to a smaller functional residual capacity per
body weight in neonates, as well as to greater tissue blood flow to the vessel-rich
group. The vessel-rich group of tissues includes the brain, heart, kidneys, and
liver. This group comprises approximately 22% of total body volume in neonates,
as compared with the 10% of total body volume in adults.
21
Q
- How does the minimum alveolar concentration (MAC) of inhaled anesthetics
change from birth to puberty?
A
- The minimum alveolar concentration (MAC) of inhaled anesthetics changes
from birth to puberty. Preterm neonates have a lower MAC than term neonates,
whose MAC is approximately 0.87% that of adults. The MAC of inhaled
anesthetic agents is highest in infants 1 to 6 months old. The MAC is 30% less in
full-term neonates for isoflurane and desflurane. Sevoflurane MAC at term is
the same as at age 1 month.
22
Q
- What is the effect of intracardiac shunting on the rapidity of anesthesia induction
with halogenated anesthetic gases?
A
- Patients with right-to-left intracardiac shunting have a slower inhaled induction
of anesthesia, due to the volume of blood bypassing the lungs and not increasing
its anesthetic level. This results in a slower rise in the arterial level of the
anesthetic and a slower induction. This effect is most pronounced with
less-soluble agents, such as desflurane and sevoflurane, and less pronounced with
more-soluble agents, such as halothane and isoflurane. Left-to-right intracardiac
shunts have little or no effect on the rapidity of induction
23
Q
- What physiologic factors increase the sensitivity of neonates to the effects of
intravenous anesthetics?
A
- Physiologic factors that make neonates more sensitive to the effects of
intravenous anesthetics include an immature blood-brain barrier and a decreased
ability to metabolize drugs. They are more sensitive to highly protein-bound
drugs because of the lower serum albumin and protein concentrations in
neonates. In many cases the increased extracellular fluid volume and volume
of distribution present in neonates offsets the increased sensitivity to intravenous
drugs when compared with adults, thereby approximately equalizing the dose
of initial intravenous injection of drug to achieve a given result. (
24
Q
- How does the dose of thiopental change between neonates and adults?
A
- The dose of thiopental required to produce loss of lid reflex is similar in neonates,
children, and adults.
25
Q
- How does the rate of plasma clearance of opioids differ between neonates and
adults?
A
- The rate of plasma clearance of opioids is decreased in neonates when compared
with adults. (55
26
Q
- Are neonates more or less sensitive to nondepolarizing neuromuscular blocking
drugs than adults? How does the initial drug dose differ between these two
groups?
A
- Neonates are more sensitive than adults to nondepolarizing neuromuscular
blocking drugs. This means that a lower plasma concentration of drug is
required to produce similar pharmacologic results. Because of an increased
extracellular fluid volume and increased volume of distribution in neonates when compared with adults, the initial dose of nondepolarizing neuromuscular
blocking drug in these two age groups is similar. This is true despite the increased
sensitivity to the drug for neonates.
27
Q
- How does the duration of action of nondepolarizing neuromuscular blocking drugs
differ between neonates and adults?
A
- The duration of action of nondepolarizing neuromuscular blocking drugs in
neonates may be prolonged while the mechanisms for clearance are still
immature in the neonate. For example, the clearance of d-tubocurarine parallels
the glomerular filtration rate at various ages. There exists a great deal of
variability among pediatric patients with regard to the duration of effect of
nondepolarizing neuromuscular blocking drugs. Monitoring of the
neuromuscular junction with a peripheral nerve stimulator is recommended when
nondepolarizing neuromuscular blocking drugs are administered to this
population
28
Q
- How does the dose of neostigmine necessary to antagonize neuromuscular
blockade in the neonate compare with the dose necessary in the adult? How does
this affect clinical practice?
A
- The dose of neostigmine necessary to antagonize neuromuscular blocking drugs
in the neonate is less than that of adults, although clinically the same dose may be
used. (
29
Q
- How does the dose of succinylcholine necessary to produce neuromuscular
blockade in the infant and neonate compare with the dose necessary in the adult?
A
- The dose of succinylcholine per body weight necessary to produce neuromuscular
blockade in the neonate and infant is increased from the adult dose. This is
presumed to be due to the increase in extracellular fluid volume and increase in
volume of distribution in neonates and infants. (551)
30
Q
- What is the recommendation for fluid maintenance and replacement in the
pediatric population?
A
- Fluid maintenance and replacement in the pediatric population is based on the
patient’s age and metabolic rate, underlying disease process, type and extent of
surgery, and anticipated fluid translocation. The maintenance rate of pediatric
patients is related to their metabolic demand, which in turn is related to the
ratio of body surface to weight. Hourly fluid requirements are estimated to be
4 mL/kg for children up to 10 kg, an additional 2 mL/kg for each kilogram of body
weight between 10 kg and 20 kg, and an additional 1 mL/kg for each kilogram
of body weight above 20 kg. Additional fluid replacement may be required for
the patient’s initial fluid deficit, third-space losses, or other losses. Fluid
replacement can be guided by the patient’s systemic blood pressure, tissue
perfusion, and urine outpu
31
Q
- What is the goal for urine output when monitoring the intraoperative volume
status of the pediatric patient
A
- A goal for urine output when monitoring the intraoperative volume status in the
pediatric patient is 0.5 to 1 mL/kg/hr. (
32
Q
- When should glucose administration be considered in the pediatric population?
A
- Glucose administration in the pediatric patient can be considered in patients
who are at a high risk for hypoglycemia. Pediatric patients at a high risk for
hypoglycemia include newborns of diabetic mothers or neonates whose
hyperalimentation has been discontinued. Maintenance fluids of 5% dextrose in
0.45 normal saline can be administered to these patients intraoperatively as a
piggy-back infusion by pump with care not to bolus glucose-containing solutions.
33
Q
- What is a reasonable approach to replace preoperative fluid deficits in pediatric
patients?
A
- Nonglucose containing isotonic fluids are most appropriate to replace losses. These
include lactated Ringer solution and Plasma-lyte A, which both contain
physiologic levels of sodium and potassium. Normal saline can be used, but
with supraphysiologic levels of sodium and chloride, a hyperchloremic,
hypernatremic, metabolic acidosis can occur with the administration of large
volumes.
34
Q
- What is a reasonable approach to replace preoperative fluid deficits in pediatric
patients?
A
- Preoperative fluid deficits in the pediatric patient can be estimated by multiplying
the number of hours the patient has been NPO by the hourly maintenance
fluid requirement based on the 4-2-1 rule. Replace 50% of this deficit in the first
hour, and the remaining 50% in the second hour. Minimizing preoperative
fluid deficits by allowing clear liquids to be ingested orally up to 2 hours before
surgery is an effective strategy to minimize preoperative deficits
35
Q
- How are third-space losses and fluid replacement estimated according to the
degree of invasiveness of the surgery? How does this contribute to an overall fluid
management strategy for pediatric patients?
A
- For minimally invasive surgery, third-space losses are estimated to be 0 to
2 mL/kg/hr. This includes superficial surgery such as strabismus repair. For mildly
invasive surgery such as ureteral reimplantation, these losses are estimated at 2 to
4 mL/kg/hr. For moderately invasive surgery such as elective bowel reanastomosis,
fluid losses are estimated at 4 to 8 mL/kg/hr; and for maximally invasive surgery
such as bowel resection for necrotizing enterocolitis, fluid losses are estimated to
be 8 to 10 mL/kg/hr or greater. To this hourly fluid administration is added the
maintenance fluid requirement according to the 4-2-1 rule, the preoperative fluid
deficit as noted previously, and replacement for blood loss. The latter is replaced
with 3 mL of isotonic crystalloid for each milliliter of estimated blood loss, or 1 mL
of colloid such as 5% albumin for each milliliter blood loss, or milliliter for milliliter
of blood product such as packed red blood cells
36
Q
- What formula can be used to help guide the anesthesiologist with blood loss
replacement?
A
- A formula that may be used by the anesthesiologist to help guide blood loss
replacement is:
MABL mL ð Þ¼ EBVðmLÞðpatient Hct minimum acceptable HctÞ=patient Hct
MABL, maximum allowable blood loss; EBV, estimated blood volume; Hct,
hematocrit. The estimated blood volume is between 70 mL/kg at about 5 years of
age to 100 mL/kg in the premature newborn. This formula should be applied to the
pediatric patient prior to surgery so that when the threshold is reached, it is
immediately recognized and the transfusion initiated.
37
Q
- What is the transfusion threshold for packed red blood cells (PRBC) in pediatric
patients? What is the expected hemoglobin increase with PRBC transfusion? What
special precautions are needed for PRBC transfusion in neonates and young
infants?
A
- The pediatric patient’s transfusion threshold varies greatly according to the
patient’s underlying physiology, age, nature of the surgery, and anticipated
ongoing blood loss, and must be individualized. For patients with cyanotic
heart disease, a hemoglobin threshold of 12 to 13 g/dL is often used. For
otherwise healthy acyanotic patients, a lower threshold of 7 to 8 g/dL is often used;
10-15 mL/kg of PRBC should increase hemoglobin by 2 to 3 g/dL. Leukocyte
reduction and irradiation of PRBCs minimizes the risk of cytomegalovirus
transmission, graft versus host reaction, and HLA allosensitization. These
procedures are used for infants less than 4 months, immunocompromised patients,
and transplant or potential transplant recipients
38
Q
- What is the indication for a platelet transfusion in pediatric patients, and what is
the expected response to platelet transfusion?
A
- The usual indication for platelet transfusion in a pediatric patient is a platelet count
below 50,000 to 100,000/dL, accompanied by surgical bleeding; 5 to 10 mL/kg of
platelet concentrate transfusion should increase platelet count by 50,000 to
100,000/dL.
39
Q
- What is the usual indication for transfusion of fresh frozen plasma (FFP) in
pediatric patients? What is the expected response to FFP administration?
A
- Indications for FFP administration in pediatric patients include massive
transfusion resulting in markedly reduced levels of coagulation proteins and
hemodilution from cardiopulmonary bypass in small infants. Ten to fifteen
milliliters per kilogram of FFP will increase most coagulation factors by 15% to
20%, which is often sufficient to improve hemostasis
40
Q
- What is the usual indication for administration of cryoprecipitate in pediatric
patients? What is the expected response to cryoprecipitate administration?
A
- Indications for cryoprecipitate administration in pediatric patients most often are
low fibrinogen concentrations from massive hemorrhage or dilution from
cardiopulmonary bypass. One unit of cryoprecipitate administered per 5 kg of
patient weight is normally sufficient to restore adequate fibrinogen levels
41
Q
- What are some other pharmacologic agents that will either reduce blood loss or
help achieve hemostasis with major blood loss surgery in pediatric patients?
A
- The lysine analogs E-aminocaproic acid and tranexamic acid reduce fibrinolysis by
inhibiting plasmin. Recombinant factor VIIa is used for patients with factor VII
deficiency or hemophiliacs with inhibitors to factors VIII and IX. It is also used
in cases of massive hemorrhage such as cardiac surgery or trauma, as a life-
saving measure to reduce bleeding. This agent causes a “thrombin burst” when
exposed to tissue factor, resulting in massive activation of the coagulation
cascade. Thrombotic complications have been reported with recombinant factor
VIIa.
42
Q
- What is the leading cause of difficult airway management in infants and young
children? What are some genetic syndromes that cause this condition?
A
- Micrognathia is the single most common cause of difficult mask ventilation and
tracheal intubation in young pediatric patients. The preoperative airway
assessment in children should involve visual inspection for micrognathia, as
well as midface hypoplasia or other cranio-facial abnormalities. Pierre-Robin
sequence, Goldenhar, and Treacher-Collins syndromes are the most commonly
encountered conditions resulting in micrognathia.
43
Q
- What is the general approach to the difficult pediatric airway, and how does it
differ from the adult difficult airway?
A
spontaneous respiration; use adjuncts such as the laryngeal mask airway,
videolaryngoscope, or fiber-optic bronchoscope to secure the airway; awaken
the patient if possible if the airway cannot be secured; avoid neuromuscular blockade
until the airway is secured; and have surgical backup for emergency tracheostomy
for particularly difficult cases. The major difference between managing the pediatric
versus adult airway is that young pediatric patients will not tolerate an “awake”
intubation with topical anesthesia of the airway; they must have some level of
moderate to deep sedation or general anesthesia. Also, cricothyrotomy is technically
difficult in small patients and ventilation via this method ineffective. Thus, this
method cannot be used in young pediatric patients.
44
Q
- What history should be obtained from a preoperative evaluation of a pediatric
patient? What are some considerations that are specific to the pediatric population
with regard to the history and physical examination?
A
- The preoperative history in the pediatric patient often comes from a parent. The
history obtained should include such things as congenital anomalies, allergies,
bleeding tendencies, and any recent exposure to communicable diseases. A special
consideration for the pediatric population is whether the patient has had any
recent upper respiratory tract infection, which makes it more likely that the
patient will have increased secretions and airway hyperreactivity with anesthesia.
Elective surgeries may be delayed in the presence of an upper airway infection. With
regard to the airway examination, the presence of loose teeth should be evaluated,
and removal of the loose tooth or teeth before airway manipulation should be
considered.
45
Q
- What preoperative laboratory data may be important in the pediatric population?
A
- Laboratory data are typically unnecessary in the routine pediatric patient.
Laboratory data should be ordered based on abnormalities in the history and
physical examination. Urine pregnancy testing is practiced for menstruating
females in many institutions.
46
Q
- What are the recommendations for the preoperative ingestion of solids and clear
liquids for pediatric patients?
A
- The recommendations for the preoperative consumption of solids and clear liquids
are now standardized. Clear liquids are generally allowed up to 2 hours before
induction of anesthesia, breast milk up to 4 hours before induction, and milk or
formula allowed up to 6 hours before induction. Solid foods should not be
ingested sooner than 6 to 8 hours before anesthesia. These guidelines apply to all
ages of pediatric patients.
47
Q
- What are some considerations regarding the choice of premedicant in the pediatric
patient? What are some drugs and their routes of administration for preoperative
medication in the pediatric population?
A
- Premedication of the pediatric patient should take into consideration the age of the
patient, the patient’s underlying medical condition, the length of surgery, the
mode of induction of anesthesia, and whether the patient will be staying in the
hospital after the procedure. Infants younger than 6 months old typically do not
require premedication, whereas patients between 9 months and 5 or 6 years old
may benefit from premedication before separation from their parents.
Premedicants may be administered orally, intravenously, intramuscularly,
rectally, sublingually, transmucosally, or intranasally; however, the oral route
is strongly preferred. One drug available and commonly used for premedication
in the pediatric population is oral midazolam
48
Q
- How can the induction of anesthesia be achieved in pediatric patients without an
intravenous catheter in place?
A
- In the pediatric patient without an intravenous catheter, anesthesia can be induced
via inhalation. An inhalation induction can be achieved by initially having
the child breathe 70% nitrous oxide and 30% oxygen, followed by incremental
increases in the concentration of a volatile anesthetic. The only volatile anesthetic available for inhalation induction in the United States is sevoflurane, because it is
much less pungent than the other volatile anesthetics. Other adjuncts that may be
used to decrease patient anxiety and facilitate the induction of anesthesia under
these circumstances include having the parents present during the time of
induction, flavoring the anesthesia mask with pleasant scents, and maintaining a
constant monotone conversation with the patient. A story can be told by the
anesthesiologist to distract the patient during induction.
49
Q
- What are some risks of an inhaled induction of anesthesia?
A
- An inhaled induction of anesthesia has some inherent risks. First, while the
pediatric patient is being induced, the anesthesiologist often increases
concentrations of the volatile anesthetic to dangerous inspired concentrations of
volatile anesthetic if maintained. Once anesthesia is induced it is important to
reduce the inspired concentrations of volatile anesthetic to routine maintenance
levels. This is especially true just before intubating the trachea, because connection
of the circuit and ventilating the intubated patient with high inspired
concentrations of volatile anesthetic while potentially distracted with
endotracheal tube positioning is a risk. High inspired concentrations of volatile
anesthetic, if continued, can lead to myocardial depression that is difficult to
reverse. Another risk of an inhaled induction of anesthesia is that of laryngospasm.
Laryngospasm, along with coughing, vomiting, and involuntary movement, can
occur in stage 2 (the excitement phase) of induction of anesthesia. Laryngospasm is
accompanied by a rocking-boat motion of the chest and abdomen as the patient
attempts to inspire against a closed glottis. Laryngospasm should be treated by
closing the pop-off valve and creating positive-pressure of about 10 cm H2O
against the glottis. If necessary, positive pressure ventilation can be attempted. In
most circumstances these will reverse the laryngospasm and the patient will
spontaneously ventilate. Should these two interventions not reverse the
laryngospasm, succinylcholine can be administered intravenously or
intramuscularly. Succinylcholine is the neuromuscular blocking drug of choice
under these circumstanc
50
Q
- What is the indication for the placement of an intravenous catheter in the pediatric
patient undergoing a surgical procedure?
A
- The placement of an intravenous catheter should be done in every pediatric patient
undergoing a surgical procedure other than for very short surgical procedures.
51
Q
- How can the anesthesiologist regulate the intravenous fluids to be administered
in the pediatric patient?
A
- The administration of intravenous fluids in pediatric patients can be regulated
by the use of a calibrated drip chamber yielding 60 drops/mL, and filled with
only 50 to 100 mL of IV fluid, so as to minimize the risk that excessive amounts of
fluid are accidentally administered
52
Q
- How can the induction of anesthesia be achieved in pediatric patients with an
intravenous catheter in place?
A
- In the pediatric patient with an intravenous catheter, the induction of anesthesia
can be achieved by the intravenous administration of an induction agent
such as thiopental or propofol. This is the induction method of choice in patients at
risk for the aspiration of gastric contents
53
Q
- How can the induction of anesthesia be achieved in pediatric patients without an
intravenous catheter in place and in whom an inhalation induction is not
possible?
A
- Another method of induction in the pediatric patient without an intravenous
catheter and in whom an inhalation induction is not possible is by the
intramuscular administration of ketamine. This method of induction is used
most commonly in developmentally delayed or severely uncooperative
children
54
Q
- What is the concern regarding the use of succinylcholine in pediatric patients?
What are some alternatives that may be used?
A
- There are multiple concerns regarding the use of succinylcholine in pediatric
patients. First, the administration of succinylcholine can result in cardiac
arrhythmias, including bradycardia and, rarely, cardiac sinus arrest. The
pretreatment of pediatric patients with atropine may reduce succinylcholine-
induced bradycardia. Second, it is believed that in patients who have been
administered succinylcholine and have subsequent masseter muscle rigidity, there
may be impending malignant hyperthermia. Finally, there have been reports of
pediatric patients who were otherwise healthy and went into irreversible cardiac
arrest after the administration of succinylcholine. Many of these patients had hyperkalemia, rhabdomyolysis, and acidosis. It is postulated that these pediatric
patients may have had undiagnosed myopathies. Postmortem muscle biopsies
have shown many of them to have muscular dystrophy. The group at highest risk of
this catastrophic event are males 8 years of age or younger. Because of these
concerns, there is now a “black box warning” by the U.S. Food and Drug
Administration prohibiting routine use of succinylcholine in pediatric patients. It
is only indicated for airway emergencies, such as laryngospasm or rapid sequence
induction. Some alternatives that may be used are the nondepolarizing
neuromuscular blocking drugs, such as larger doses of vecuronium or rocuronium.
55
Q
- Under what circumstances is succinylcholine accepted for use for neuromuscular
blockade in the pediatric population?
A
- Succinylcholine is accepted for use for rapid onset neuromuscular blockade in
pediatric patients for the treatment of laryngospasm and in patients at high risk for
aspiration of gastric contents in whom rapid sequence induction/intubation is
indicated. (
56
Q
- What are some physiologic characteristics of the pediatric airway that differ from
the adult airway?
A
- There are multiple physiologic differences between the pediatric airway and the adult
airway. Pediatric patients tend to have a larger tongue relative to the size of their
mouths. Particularly true in neonates is that the occiput is larger, so that placing the
head in the neutral position naturally places the head in a position favorable for direct
laryngoscopy. Extending the head can make direct laryngoscopy difficult. Thelarynx
is more cephalad in pediatric patients, with the cricoid cartilage opposing the C4
vertebra rather than the C6 vertebra as in adults. The larynx is also more anterior. The
epiglottisislonger, stiffer, andU shaped and hasmore of a horizontallie. The narrowest
point of the airway is at the level of the cricoid cartilage in the presence of
neuromuscular blockade. These differences between the pediatric airway and the adult
airway are present until about the age of 8 years, after which the difference between the
pediatric airway and the adult airway is mainly just a difference in size.
57
Q
- Why has the classic teaching that uncuffed endotracheal tubes should be used for
intubating the trachea of pediatric patients under the age of 8 years changed?
A
- Because the narrowest point of the pediatric airway is at the level of the cricoid
cartilage, it was believed that an endotracheal tube that passes easily through the
larynx may cause ischemia or damage to the trachea distally. However, recent
imaging studies challenge this notion, and the difference in diameter between
the larynx and subglottis in younger children is minimal. Historically, uncuffed
tubes were the standard of care in children younger than 8 years of age owing
to concerns about subglottic stenosis and postextubation stridor. However, with
the introduction of tubes with high volume–low pressure cuffs, recent studies
suggest that there is no increased risk of airway edema with cuffed endotracheal
tubes and that the use of cuffed endotracheal tubes may decrease the number
of laryngoscopies and intubations due to inappropriate tube size. The risk of
postintubation tracheal edema is greatest in children between 1 and 4 years of age,
whether a cuffed or uncuffed ETT is used. Postintubation tracheal edema/croup can
be treated with humidified gases and aerosolized racemic epinephrine.
Dexamethasone has also been administered intravenously for the treatment of
postintubation tracheal edema.
58
Q
- What is the benefit of the administration of heated and humidified gases or using
a condenser humidifier in children undergoing prolonged operations?
A
- Because of their larger surface area to weight ratio, infants tend lose body heat
much more rapidly than adults. This is particularly true in a cold operating room
environment. The administration of heated and humidified gases or use of a
condenser humidifier in children undergoing prolonged operations is useful in
decreasing intraoperative heat loss and in avoiding decreases in body temperature.
Warming the operating room, the use of radiant warmers, and warmed intravenous
fluids are other methods of maintaining normothermia
59
Q
- What are some signs the clinician may use to determine the adequacy of the depth
of anesthesia for surgery in the pediatric population?
A
- Signs for the adequacy of depth of anesthesia for surgery are the same for neonates,
infants, and children as they are in adults. Those signs include blood pressure,
heart rate, and skeletal muscle movement. Processed electroencephalographic
technologies may be used as in the adult population, but are less reliable in
younger children. (556
60
Q
- When hypotension accompanies the administration of volatile anesthetics to
neonates, what is it likely to be indicative of?
A
- Hypotension in the neonate that accompanies the administration of volatile
anesthetics is likely to be indicative of hypovolemia. (552)
61
Q
- How does intraoperative monitoring in the pediatric population differ from
intraoperative monitoring in the adult population?
A
- Intraoperative monitoring in the pediatric population is not any different from
intraoperative monitoring in the adult population undergoing comparable surgical
procedures. Routine monitors should include blood pressure, heart rate,
electrocardiogram, peripheral oxygen saturation, capnography, anesthetic gas
concentration, and temperature monitoring. (5
62
Q
- What problem may be encountered with the monitoring of end-tidal carbon
dioxide concentrations in pediatric patients?
A
- The monitoring of end-tidal carbon dioxide concentrations in small children,
infants, and neonates may be complicated by large dead space introduced
between the CO2 sampling line and the trachea by endotracheal tube connectors,
condenser humidifiers, and elbow connectors at the end of the Y-piece of the
anesthesia circuit. The small tidal volumes of these patients exacerbate the
problem and can result in falsely low end-tidal CO2 readings. In addition,
congenital heart disease patients with right-to-left shunting will have a falsely low
end-tidal CO2 due to the blood bypassing the lungs. (556)
63
Q
- How should the size of a blood pressure cuff be selected? What errors in blood
pressure measurement may be encountered with an erroneously sized cuff?
A
- An appropriately sized blood pressure cuff is one that is greater than one third
of the circumference of the limb. A blood pressure cuff that is too small will
result in artificially high blood pressures. The opposite is also true, that a blood
pressure cuff that is too large will result in artificially low blood pressures. (556)
64
Q
- What veins may be used to monitor the central venous pressure in the neonate?
In infants? In children?
A
- Central venous pressure can be monitored in the neonate via an umbilical vein
catheter. The internal jugular vein, femoral vein, or subclavian vein can be used
for central venous pressure monitoring in neonates, infants, and children. (549)
65
Q
- What are some regional anesthetic blocks that can be administered in the pediatric
population?
A
- There are several procedures in which regional anesthetic techniques can be
considered in the pediatric population. For circumcision or hypospadias repair,
a penile block may be used. For inguinal hernia repair an ilioinguinal and
iliohypogastric block may be used. For femur surgery, a fascia iliaca compartment
block may be used. For arm and wrist surgery a brachial plexus block may be used.
Intravenous regional anesthesia may also be used in the pediatric patient for tendon
laceration repairs or extremity fractures. Caudal anesthesia is a common form of
anesthesia and is used for postoperative pain relief in the pediatric population in
whom the surgical site is below the level of the diaphragm. Conversely, a lumbar
epidural anesthetic may also be used in the pediatric patient. (557, 558)
66
Q
- What local anesthetic and what dose is commonly used in a caudal anesthetic?
What is the approximate duration of the postoperative pain relief obtained from
this caudal anesthetic? How is the length of the dural sac different in children and
adults?
A
- For caudal epidural anesthesia, the local anesthetic most commonly used is
bupivacaine at a concentration of 0.125% to 0.25%, and ropivacaine at 0.1% to
0.2%. The volume is 0.5 to 1 mL/kg, up to a maximum of 20 mL. The duration of pain
relief provided by this dose of local anesthetic in the caudal epidural space is 4 to
6 hours, therefore possibly providing some postoperative pain relief. The dural sac
extends more caudad in children than in adults, making inadvertent intrathecal
injection a possibility. The risks of caudal epidural anesthesia are minimal. (557)
