Lippincott's Anesthesia Review: 1001 Questions and Answers

Chapter 18. Pediatric Anesthesia

Dipty Mangla and Ashish Sinha

    1.   Correct statement regarding neonatal physiology is

          A.   Neonates have a greater volume of distribution for water-soluble drugs

          B.   Total body water is higher in adults

          C.   Dose of propofol (mg/kg) is lower in neonates than in adults

          D.   Neonates have a higher body fat content than adults

    2.   A 4-year-old child weighing 16 kg is scheduled for hernia repair under general anesthesia. Assuming he was NPO for 8 hours, his total fluid deficit will be about _____ (mL):

          A.   380

          B.   420

          C.   460

          D.   500

    3.   The total dose of midazolam that may be given orally as premedication is

          A.   0.2 mg/kg, maximum 10 mg

          B.   0.2 mg/kg, maximum 20 mg

          C.   0.5 mg/kg, maximum 15 mg

          D.   0.5 mg/kg, maximum 20 mg

    4.   A newborn baby of 37 weeks of gestation has a heart rate of 90 bpm, is crying, is pink with blue extremities, and shows some flexion. Her Apgar score would be

          A.   6

          B.   7

          C.   8

          D.   9

    5.   After initial evaluation of the baby described above, the next step in managing her would be

          A.   Provide positive-pressure ventilation

          B.   Chest compressions

          C.   Warming blanket

          D.   Cardiology consult

    6.   All of the following drugs can be given through endotracheal tube, except

          A.   Epinephrine

          B.   Lidocaine

          C.   Surfactant

          D.   Calcium

    7.   The disease or syndrome with known association with malignant hyperthermia is

          A.   Huntington chorea

          B.   Fabry disease

          C.   King Denborough syndrome (KDS)

          D.   Burns

    8.   An 8-year-old child is brought to the emergency room with testicular torsion. The parents tell you he ate a sandwich 6 hours ago. Surgeon wants to operate immediately. Your response should be

          A.   Take him to the OR, deem it emergent, rapid-sequence intubation

          B.   Wait for 2 more hours, deem it urgent, rapid-sequence intubation

          C.   He is adequately fasting, elective, intubation

          D.   Wait for 2 hours, elective, intubation

    9.   Which of the following statements about pediatric airway is true?

          A.   More caudal position of larynx as compared to adult

          B.   More acute angulation of epiglottis

          C.   Glottic opening is the narrowest part of airway

          D.   Longer trachea as compared to adults

  10.   A 10-week-old baby, who was born prematurely at 30 weeks of gestation, undergoes circumcision uneventfully under general anesthesia. After the baby recovers from anesthetics in postanesthesia care unit, he can/should be

          A.   Admitted and monitored for 24 hours

          B.   Discharged home with parents

          C.   Discharged home if parents live within a 30-minute radius

          D.   Admitted to the ICU

  11.   Hypertrophic pyloric stenosis is associated with

          A.   Metabolic acidosis

          B.   Metabolic alkalosis

          C.   Hyperkalemia

          D.   Hyperchloremia

  12.   A child with which of the following diseases/syndromes should be evaluated for heart disease?

          A.   Omphalocele

          B.   Gastroschisis

          C.   Hypertrophic pyloric stenosis

          D.   Tracheobronchitis

  13.   The earliest and the most pathognomic feature of malignant hyperthermia (MH) is

          A.   Increased temperature

          B.   Increased end-tidal CO2

          C.   Increased heart rate

          D.   Increased respiratory rate

  14.   The most common type of tracheoesophageal fistula (TEF) is

images

Figure 18-1.

  15.   Down syndrome is associated with all of the following, except

          A.   Large tongue

          B.   Atlantooccipital instability

          C.   Hyperthyroidism

          D.   Increased incidence of seizures

  16.   The first sign of intrathecal injection following the placement of caudal epidural with 0.25% bupivacaine in a 1-year-old child would be

          A.   Hypotension

          B.   Bradycardia

          C.   Falling oxygen saturation

          D.   Tachycardia

  17.   A 2-year-old child weighing 13 kg is scheduled for inguinal hernia repair. The calculated dose of 0.25% bupivacaine for a caudal epidural would be approximately ______ (mL):

          A.   13

          B.   7

          C.   10

          D.   20

  18.   All the following are physiologic changes that occur at birth, except

          A.   Closure of foramen ovale

          B.   Closure of ductus arteriosus

          C.   Decreased right-ventricular afterload

          D.   Decreased left-ventricular afterload

  19.   Neonates lose heat by all the following mechanisms in the operating room, except

          A.   Conduction to cold surfaces

          B.   Exposure to cold operating room

          C.   Dry airway gases

          D.   Metabolism of brown fat

  20.   A 4-year-old child with tetralogy of Fallot is scheduled for incision and drainage of a foot abscess. All the following measures can be used to improve his oxygenation, except

          A.   Phenylephrine

          B.   Nitroglycerine

          C.   Nitric oxide

          D.   Epinephrine

  21.   Which of the following heart rates is inappropriate for the age?

          A.   50 bpm at 12 years of age

          B.   120 bpm for a neonate

          C.   100 bpm for a 1-year-old

          D.   80 bpm for a 3-year-old

  22.   The age at which the glomerular filtration rate in a child is same as in adults is

          A.   6 months

          B.   1 year

          C.   1.5 years

          D.   2 years

  23.   Normal blood glucose level in a neonate is ______ (mg/dL):

          A.   20 to 40

          B.   40 to 60

          C.   60 to 70

          D.   50 to 80

  24.   The recommended size of an endotracheal tube for a 1-year-old child is

          A.   2.5

          B.   3.0

          C.   4.0

          D.   5.0

  25.   As compared to a 10-year-old child, a 1-year-old child will have higher

          A.   Oxygen consumption

          B.   Functional residual capacity

          C.   Tidal volume

          D.   Vital capacity

  26.   The total blood volume in a preterm is ______ (mL/kg):

          A.   90 to 100

          B.   70 to 80

          C.   50 to 60

          D.   80 to 90

  27.   A 2-year-old is scheduled for elective tonsillectomy and adenoidectomy. His mother tells you he has runny nose. Your decision whether to proceed will be based on all the following, except

          A.   If he is afebrile

          B.   If he is not actively wheezing

          C.   Cancel the surgery since it is elective

          D.   Reluctance of parent for admitting the child, if needed

  28.   Urine output in a 6-year-old child undergoing surgery under general anesthesia should be ______ (mL/kg/h):

          A.   0.5

          B.   1

          C.   1.5

          D.   2

  29.   Perioperative management of a child with a femur fracture and sickle cell disease includes all of the following, except

          A.   Hydration

          B.   Treat infections

          C.   Transfuse to hemoglobin of 14 mg/dL

          D.   Avoid metabolic acidosis

  30.   Anesthetic management of a 12-year-old with Down syndrome includes all of the following, except

          A.   Continue antiseizure medications

          B.   Heavy sedation since all such patients are combative

          C.   Prepare for manual in line neck stabilization

          D.   Radiographs of the neck should be reviewed to rule out atlantooccipital instability

  31.   An 8-year-old boy, weighing 30 kg, is undergoing resection of a Wilms tumor in the operating room. His starting hemoglobin is 12 g/dL. If the threshold for transfusion is 8 g/dL, the allowable blood loss is ______ (mL):

          A.   820

          B.   840

          C.   860

          D.   880

  32.   A 5-year-old otherwise-healthy child is undergoing strabismus surgery with a laryngeal mask airway (LMA) in place. Thirty minutes into the procedure, his heart rate is 60 bpm, blood pressure is 90/60 mm Hg, and the pulse oximeter reads 98%. The next step in management should be

          A.   Replace the LMA with an endotracheal tube

          B.   Inform surgeon, administer atropine

          C.   Nothing, this is normal for this child

          D.   Increase the FIO2 to 1.0

  33.   The afferent limb for oculocardiac reflex is

          A.   Vagus nerve

          B.   Trigeminal nerve

          C.   Glossopharyngeal nerve

          D.   Facial nerve

  34.   Positive-pressure ventilation with a face mask is contraindicated in which of the following condition?

          A.   Laryngospasm

          B.   Congenital diaphragmatic hernia

          C.   Trauma

          D.   Asthma

  35.   Treatment of postintubation croup in a child who underwent adenoidectomy is

          A.   Inhalation of mist

          B.   Steroids

          C.   Racemic epinephrine

          D.   All of the above

  36.   The most important measure to avoid subglottic edema in children is

          A.   Use of an appropriate-size endotracheal tube

          B.   Lubricating the endotracheal tube prior to intubation

          C.   Administering intravenous lidocaine for all intubations

          D.   Administering intravenous steroids for all intubations

  37.   Important difference between epiglottitis and laryngotracheobronchitis (croup) is

          A.   Croup responds to racemic epinephrine and steroids

          B.   Croup occurs in older children

          C.   Higher temperatures are seen in croup patients

          D.   Etiology of croup is bacterial

  38.   Anesthesia in a patient with Pierre Robin syndrome can be complicated by

          A.   Renal failure

          B.   Tendency to develop malignant hyperthermia

          C.   Cardiac failure

          D.   Difficult airway

  39.   Basic metabolic rate in children is

          A.   Least at 1 year of age

          B.   Same as adults

          C.   Highest till 2 years of age

          D.   Decreases after puberty

  40.   The percentage of patients developing malignant hyperthermia (MH) after masseter spasm is

          A.   0% to 24%

          B.   25% to 49%

          C.   50% to 74%

          D.   75% to 100%

  41.   All of the following are true for children with congenital diaphragmatic hernia (CDH), except

          A.   Pulmonary hypoplasia may be present

          B.   Dextrocardia is common

          C.   Bag and mask ventilation is contraindicated

          D.   Surgical management takes precedence over medical management

  42.   To protect lungs in a child with tracheoesophageal fistula, all the following should be done, except

          A.   Avoid feeding

          B.   Upright position

          C.   Intermittent suction of upper blind esophageal pouch

          D.   Prophylactic intravenous steroids

  43.   The main factor responsible for physiologic closure of a patent ductus arteriosus is

          A.   Increased PaCO2

          B.   Increased PaO2

          C.   Increased pulmonary artery pressure

          D.   Administration of nonsteroidal anti-inflammatory agents

  44.   The most effective method for maintaining normothermia in an operating room is

          A.   Warm humidified gases

          B.   Warm intravenous fluids

          C.   Warming blankets

          D.   Increasing the room temperature

  45.   A 2-year-old child undergoing myringotomy develops laryngospasm in the operating room. The patient is breathing spontaneously with face mask at an FIO2 of 0.6. Next step in the management would be

          A.   Increasing FIO2 to 1.0

          B.   Jaw thrust

          C.   Endotracheal intubation

          D.   Intramuscular succinylcholine

  46.   Normal pulmonary dead space in a neonate is ______ (mL/kg):

          A.   1

          B.   2

          C.   3

          D.   4

  47.   Which of the following statements regarding fetal hemoglobin is true?

          A.   It is composed of two α and two β chains

          B.   It has more affinity for oxygen than adult hemoglobin

          C.   Patients with sickle cell disease and high fetal hemoglobin have poor prognosis

          D.   None of the above

  48.   Compared to adults, oxygen desaturation is more frequent in pediatric population because of

          A.   Lower functional residual capacity (FRC) in children

          B.   Higher oxygen consumption in adult

          C.   Lower heart rate in adults

          D.   Lower functional residual capacity in adults

  49.   The most consistent sign of intravascular injection following caudal epidural with 0.25% bupivacaine with 1:200,000 epinephrine is

          A.   Tachycardia

          B.   ST segment changes

          C.   Bradycardia

          D.   Hypertension

  50.   The dose of nondepolarizing muscle relaxants in a neonate is

          A.   Decreased as compared to adults

          B.   Increased as compared to adults

          C.   Same as adults

          D.   Cannot be predicted

CHAPTER 18 ANSWERS

    1.   A.   Total body water in a term neonate is 75% of the total body weight, as compared to 60% in adult males and 55% in adult females. Water-soluble drugs will have an increased volume of distribution because of increased body water. Propofol dose (mg/kg) will be higher in neonates and infants than adults.

    2.   B.   Maintenance fluid requirements to replace fluid deficits accounting for a period of fasting can be calculated by the following formula.

Table 18-1  Calculation of maintenance fluid requirements

Weight

Hourly Fluid Requirement

<10 kg

4 mL/kg

10–20 kg

40 mL + 2 mL/kg > 10 kg

>20 kg

60 mL/kg + 1 mL/kg > 20 kg

          Thus using above formula, total fluid deficit would be 40 + (6 × 2) = 52 mL/h.

          Accounting for 8 hours of fasting, total fluid deficit will be 52 × 8 = 416 mL.

    3.   D.   Preoperatively, midazolam is the most common medication given for sedation and anxiety. Midazolam can be given orally in a dose of 0.25 to 0.5 mg/kg (maximum dose of 20 mg) in children. Sedative premedication is generally omitted for neonates, infants, and sick children. Oral ketamine (4–6 mg/kg) can also be used as premedication. For uncooperative children, intramuscular midazolam (0.1–0.15 mg/kg, maximum of 10 mg) and ketamine (0.02 mg/kg) can be used.

    4.   B.   Apgar scores recorded at 1 minute and 5 minutes after birth remains a valuable method for assessment of the well-being of a neonate.

Table 18-2  Apgar Score

images

          Apgar score in this case would be 1 + 2 + 1 + 2 + 1 = 7.

    5.   A.   Indications of positive-pressure ventilation in a newborn include apnea, gasping respirations, persistent central cyanosis with 100% oxygen, and heart rate less than 100 bpm. Assisted ventilation by bag and mask should be at a rate of 30 to 60 bpm with 100% oxygen. If after 30 seconds the heart rate is less than 80 bpm, chest compressions should be started and the neonate should be intubated (Fig 18-2).

images

Figure 18-2.  Reused with permission from Kattwinkel J, Perlman JM, Aziz K, et al. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science. Part 15: Neonatal Resuscitation. Circulation. 2010;122:S909–S919.

    6.   D.   Lidocaine, epinephrine, atropine, and vasopressin can be delivered down a catheter whose tip extends beyond the endotracheal tube. The dose of drugs through endotracheal tube is 2 to 2.5 times the intravenous dose. Surfactant can be given through endotracheal tube in children with severe bronchopulmonary dysplasia.

    7.   C.   Musculoskeletal diseases associated with a relatively high incidence of malignant hyperthermia include Duchenne muscular dystrophy, myotonia, and KDS. KDS is seen primarily in young boys who exhibit short stature, mental retardation, cryptorchidism, kyphoscoliosis, pectus deformity, slanted eyes, low-set ears, webbed neck, and winged scapulae.

    8.   A.   A male presenting with sudden onset of acute scrotal pain in the absence of trauma should be suspected to have testicular torsion. Testicular torsion requires immediate investigation and possible surgery to preserve potentially viable testis. Surgery should be performed within 6 hours of onset of pain to save the testicle. The salvage rate decreases to 50% if surgery is delayed between 6 and 12 hours. Children with suspected torsion of testis are assumed to have a full stomach and should have a rapid-sequence endotracheal intubation. The surgery is emergent and the patient needs to be taken to the OR.

Table 18-3  Preanesthesia Fasting Guidelines for Pediatric Patients

Product

Minimal Fasting Time

Clear liquids

2 hours

Breast milk

4 hours

Infant formula, Jell-O

6 hours

Solid food

8 hours

    9.   B.   Neonates and infants have a larger head and tongue, an anterior and cephalad epiglottis and larynx, and a short trachea and neck. The larynx is at a vertebral level of C4 versus C6 in adults. The narrowest portion of larynx in children is at the level of cricoid cartilage as compared to glottic opening in adults. An adult’s epiglottis is flat and broad, and its axis is parallel to that of trachea, whereas an infant’s epiglottis is typically narrower, omega-shaped, and angled away from the axis of trachea.

  10.   A.   Premature infants who are less-than-50-weeks postconceptional age at the time of surgery are prone to postoperative apneic episodes for up to 24 hours. Besides prematurity, other risk factors for postanesthetic apnea include hematocrit <30% (anemia), hypothermia, and neurological abnormalities. Thus, elective or outpatient procedures should be deferred until the preterm infant reaches the age of at least 50 weeks’ postconception. These patients should be monitored for 12 to 24 hours postoperatively with pulse oximetry.

  11.   B.   Hypertrophic pyloric stenosis causes stasis of gastric contents and thus leads to persistent vomiting. This can lead to depletion of sodium, potassium, chloride, and hydrogen ions, causing a hypochloremic metabolic alkalosis. Patients are first medically stabilized (correction of volume-deficit and metabolic alkalosis), and then a pyloromyotomy is performed. Hydration should be done with a sodium chloride solution supplemented with potassium (avoidance of ringer lactate as it is metabolized to bicarbonate).

  12.   A.   Both gastroschisis and omphalocele are congenital disorders characterized by defects in the abdominal wall. Omphaloceles have a hernia sac, and are often associated with other congenital anomalies (trisomy 21, diaphragmatic hernia, cardiac and bladder anomalies). Gastroschisis, on the other hand, does not have a hernia sac, and is often an isolated finding. The latter is a more serious condition, as the absence of a hernial sac can lead to dehydration, hypothermia, and infection.

  13.   B.   MH is a rare but potentially fatal hypermetabolic disorder triggered by exposure to volatile inhalational anesthetics or succinylcholine. The incidence of MH is 1:15,000 in pediatric population and 1:50,000 in adults. Signs of MH include masseter muscle rigidity, tachycardia, tachypnea, hypercarbia (increased CO2 production—earliest sign), and hyperthermia (late sign). Hypertension and arrhythmias may be seen (sympathetic overactivity). Generalized muscle rigidity is not consistently present, and presence of dark-colored urine indicates myoglobinuria.

  14.   C.   Among the different types of TEF, the most common is the type IIIB. This is where the upper esophagus ends in a blind pouch and a lower esophagus that connects to the trachea. At birth, TEF is suspected by failure to pass a catheter into the stomach and visualization of the catheter coiled in the blind upper esophageal pouch. Typically, breathing leads to gastric distension and feeding leads to choking and cyanosis. TEF patients are, therefore, prone to pulmonary aspiration. Coexistence of cardiac congenital anomalies is common. TEF patients may have associated vertebral defects, anal atresia, and radial dysplasia, known as the VATER syndrome. Addition of cardiac and limb anomalies is called the VACTERL variant.

  15.   C.   Down syndrome or trisomy 21 is one of the most common congenital syndromes in pediatric population. Anesthetic considerations in these patients include presence of short neck and large tongue (possible difficult airway), irregular dentition, mental retardation, hypotonia, congenital heart disease in 30% to 40% of patients (particularly endocardial cushion defects and ventricular septal defect), subglottic stenosis, tracheoesophageal fistula, chronic pulmonary infections, seizures, duodenal stenosis, and delayed gastric emptying.

  16.   C.   Unlike older children and adults, subarachnoid and epidural blockade in infants and small children is characterized by hemodynamic stability, even when the level of block reaches upper dermatomes. Young children rely more on the diaphragm for maintaining tidal volumes; thus, apnea may be the first sign of total spinal in infants and small children.

  17.   B.   Armitage formula can be used for calculation of caudal bupivacaine in a child with appropriate weight for his age.

          0.5 mL/kg for a lumbosacral block

          1 mL/kg for a thoracolumbar block

          1.25 mL/kg for a midthoracic block

          0.25% Bupivacaine up to a maximum of 20 mL

  18.   D.   Fetal circulation is associated with increased pulmonary vascular resistance, decreased pulmonary blood flow, decreased systemic vascular resistance, and right to left blood flow through patent ductus arteriosus and foramen ovale. At birth, the onset of spontaneous ventilation and elimination of placental circulation decreases pulmonary vascular resistance and increases pulmonary blood flow. Simultaneously, systemic vascular resistance increases, left-atrial pressure increases, foramen ovale closes functionally, and right-to-left shunting ceases. When anatomic closure is achieved and the cardiac anatomy is normal, shunting through ductus arteriosus ceases.

  19.   D.   Neonates are susceptible to increased heat losses due to thin skin, low fat content, and a higher relative body surface area. Cold operating room, wound exposure, unwarned intravenous fluid administration, dry anesthetic gases, and the direct effect of anesthetic agents on temperature regulation can further accelerate heat loss. Hypothermia is associated with delayed awakening from anesthesia, cardiac irritability, respiratory depression, increased pulmonary vascular resistance, altered drug responses, delayed wound healing, and coagulation and platelet dysfunction. Metabolism of brown fat is responsible for heat production in infants.

  20.   D.   Tetralogy of Fallot consists of right-ventricular obstruction, right-ventricular hypertrophy, and a ventricular septal defect with an overriding aorta. About 20% of patients also have pulmonic stenosis. Anesthetic management of a child with tetralogy of Fallot includes adequate preoperative hydration, avoiding factors that can increase pulmonary vascular resistance, maintaining systemic vascular resistance (SVR), and avoid increases in heart rate that may worsen infundibular stenosis. Hypercyanotic spells are treated by volume administration, sedation, and administration of drugs that increase SVR such as phenylephrine. Propranolol may be given to relieve infundibular spasm. Epinephrine in this situation may worsen cyanosis by increasing HR and decreasing SVR.

  21.   A.   Normal cardiovascular variables in children:

Table 18-4

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  22.   D.   Premature neonates have decreased creatinine clearance, impaired sodium retention, glucose excretion, and bicarbonate reabsorption, and poor diluting and concentrating ability. Normal kidney function may develop anywhere from 6 months to 2 years of age. Therefore, it is extremely important to pay meticulous attention to fluid management in children less than 2 years of age.

  23.   B.   Laboratory value of blood glucose in children:

Table 18-5

images

  24.   C.   The approximate diameter inside the endotracheal tube can be estimated by a formula based on age:

Tube diameter in mm = (Age in years/4) + 4

          Exceptions include premature neonates (2.5- to 3.0-mm tube) and full-term neonates (3.0- to 3.5-mm tube).

          Formula for the length of endotracheal tube at the lip:

Length = 12 + Age/2

  25.   A.   Metabolic rate and oxygen consumption are higher in infants than in older children. Rest of the parameters in the question remain the same per weight basis in younger and older children. Respiratory rate is increased in neonates and gradually falls to adult levels by adolescence. Airway resistance is increased in neonates due to a relative paucity of small airways. The high metabolic rate and oxygen consumption limit oxygen reserves during periods of apnea (e.g., intubation) and predispose neonates and infants to atelectasis and hypoxemia.

  26.   A.   Developmental changes in blood volume:

Table 18-6

Age

Blood Volume (mL/kg)

Preterm

90–105

Term neonate

78–86

1–12 Months

73–78

1–3 Years

74–82

4–6 Years

80–86

7–18 Years

83–90

Adults

68–88

  27.   C.   Presence of an acute purulent upper respiratory infection, fever, change in mental status, or signs of lower respiratory tract infection (wheezing, rales), especially in a child, is sufficient to postpone the surgery.

          Factors affecting decision for elective surgery in a child with upper respiratory tract infection are as follows:

          Pros

          •   Presence of runny nose alone

          •   Active, happy child

          •   Older child

          •   Clear lungs

          Cons

          •   Recent development of symptoms within 1 to 2 days

          •   Lethargic child

          •   Purulent nasal discharge

          •   Wheezing, rales

          •   Child <1 year, ex-premature

          •   Major surgery

  28.   A.   Urine output should be monitored in all children undergoing surgeries involving major fluid shifts. The fluid therapy should be aimed at maintaining a urine output of 1 mL/kg/h.

  29.   C.   Optimal preoperative preparation in patients with sickle cell anemia includes adequate hydration, treatment of infections, and an acceptable hemoglobin concentration. Preoperative transfusion therapy in sickle cell patients is individualized to the patient and to the surgical procedure. The goal of transfusion therapy is to achieve a hematocrit of 35% to 40%, with 40% to 50% normal hemoglobin. Hemoglobin desaturation or low-flow states (stasis) should be avoided in sickle cell patients. Therefore, tourniquet use should be avoided during surgical procedures. Conditions that could cause hemoglobin desaturation or stasis include hypothermia or hyperthermia, acidosis, hypoxemia, hypotension, or hypovolemia.

  30.   B.   Patients with Down syndrome exhibit a short neck, irregular dentition, mental retardation, hypotonia, large tongue, congenital heart disease (in 40% of patients, endocardial cushion defects, ventricular septal defect), subglottic stenosis, tracheoesophageal fistula, chronic pulmonary infections, and seizures. Down syndrome patients often have a difficult airway (use of smaller size of the endotracheal tube). Excessive neck flexion during laryngoscopy or intubation may result in atlantooccipital dislocation because of the laxity of the ligaments. Postoperative stridor and apnea are common in these patients. Antiseizure medications should be continued perioperatively.

  31.   B.   Maximum allowable blood loss during surgery can be calculated by the following formula:

Maximum allowable blood loss = Patient’s hemoglobin − Allowed hemoglobin/Average of the two × EBV

EBV or expected blood volume = 70 mL/kg × weight of the child

  32.   B.   Traction on extraocular muscles or pressure on the eyeball can result in cardiac dysrhythmias (bradycardia, ventricular ectopy, ventricular fibrillation). This reflex, called the oculocardiac reflex, consists of a trigeminal afferent and a vagal efferent pathway. The reflex can occur in patients undergoing ocular procedures such as cataract extraction, enucleation, and retinal detachment repair. In awake patients, the oculocardiac reflex may be associated with somnolence and nausea. Management of the oculocardiac reflex consists of (1) immediate notification to the surgeon and temporary cessation of surgical stimulation, (2) confirmation of adequate ventilation, oxygenation, and depth of anesthesia, (3) administration of intravenous atropine (10 μg/kg) if the conduction disturbance persists, and (4) infiltration of the rectus muscles with local anesthetic. Also, retrobulbar block performance can elicit the oculocardiac reflex.

  33.   B.   Traction on extraocular muscles or pressure on the eyeball can result in cardiac dysrhythmias (bradycardia, ventricular ectopy, ventricular fibrillation). This reflex, called the oculocardiac reflex, consists of a trigeminal afferent and a vagal efferent pathway. The reflex can occur in patients undergoing ocular procedures such as cataract extraction, enucleation, and retinal detachment repair. In awake patients, the oculocardiac reflex may be associated with somnolence and nausea. Management of the oculocardiac reflex consists of (1) immediate notification to the surgeon and temporary cessation of surgical stimulation; (2) confirmation of adequate ventilation, oxygenation, and depth of anesthesia; (3) administration of intravenous atropine (10 μg/kg) if the conduction disturbance persists; and (4) infiltration of the rectus muscles with local anesthetic. Also, retrobulbar block performance can elicit the oculocardiac reflex.

  34.   B.   Positive pressure with a face mask can be a lifesaving temporizing measure in situations such as laryngospasm, hypoxia, and even difficult intubation. However, it is contraindicated in situations where there is an increased risk of aspiration. In patients with congenital diaphragmatic hernia and tracheoesophageal fistula, positive-pressure ventilation with a face mask is relatively contraindicated.

  35.   D.   Perioperative postintubation croup occurs in 0.1% to 1% of children. Factors associated with increased risk of croup include a larger outer diameter of endotracheal tube relative to airway, frequent patient position changes, multiple intubation attempts, traumatic intubation, and children aged 1 to 4 years. Treatment includes humidified mist, nebulized racemic epinephrine, and dexamethasone.

  36.   A.   Perioperative postintubation croup occurs in 0.1% to 1% of children. Factors associated with increased risk of croup include a larger outer diameter of endotracheal tube relative to airway, frequent patient position changes, multiple intubation attempts, traumatic intubation, and children aged 1 to 4 years. Treatment includes humidified mist, nebulized racemic epinephrine, and dexamethasone.

  37.   A.   Croup is upper airway obstruction characterized by a barking cough. It could be postintubation croup or a result of viral infection. Incidence of infectious croup is increased in children aged 3 months to 3 years. Infectious croup progresses slowly, and patients rarely require intubation. It is treated with nebulized racemic epinephrine and dexamethasone. Acute epiglottitis is a bacterial infection commonly due to Haemophilus influenzae type B. It affects children of 2 to 6 years old. Acute epiglottitis can rapidly progress from a sore throat to complete airway obstruction. Endotracheal intubation (spontaneous breathing inhalational induction in sitting position) and antibiotic therapy can be lifesaving.

  38.   D.   Pierre Robin syndrome is a genetic disorder characterized by hypoplastic mandible, pseudo macroglossia, and high arched and cleft palate. Large tongue and small mouth can lead to both difficult ventilation and intubation.

  39.   C.   Children have a higher metabolic rate than adults until 2 years of age. Pediatric patients have a larger surface area per kilogram than adults (increased surface area/weight ratio). Besides the higher surface area accounting for the higher metabolic rate, children (especially neonates) also loose heat to a greater extent.

  40.   B.   Masseter muscle spasm (MMS) may be seen in pediatric patients after the administration of succinylcholine. About 50% of patients in whom MMS develops prove to be susceptible to MH by muscle testing.

  41.   D.   During fetal development, the gut can herniate into the thorax through diaphragmatic defects, with left-sided herniation is the most common type (90%). The reported incidence of diaphragmatic hernia is about 1:5000 live births. Clinical features of diaphragmatic herniation include hypoxia, a scaphoid abdomen, and evidence of bowel in the thorax (confirmed with auscultation or radiography). Pulmonary hypoplasia and malrotation of the intestines are commonly associated. While the ipsilateral lung is particularly affected, the herniated gut can compress and retard the maturation of both the lungs. Pulmonary hypertension is common. CDH is often associated with dextrocardia. The goal of initial management of CDH is to avoid a surgical intervention when the infant is hypoxic and acidotic. Instead, medical management is directed to stabilizing the infant’s cardiorespiratory status by improving oxygenation, correcting metabolic acidosis, reducing the right-to-left shunting, and increasing pulmonary perfusion.

  42.   D.   Interventions to protect the lungs from aspiration in the presence of tracheoesophageal fistula include

          •   Avoidance of feedings

          •   Upright positioning of the infant to decrease the likelihood of gastroesophageal reflux (30-degree elevation)

          •   Antibiotic therapy and physiotherapy if pneumonia is diagnosed

          •   Intermittent suctioning of the upper blind esophageal pouch

  43.   B.   At birth, initiation of spontaneous ventilation and elimination of the placental circulation decrease pulmonary vascular resistance and increase pulmonary blood flow. At the same time, systemic vascular resistance increases, left-atrial pressure increases, foramen ovale closes functionally, and the right-to-left shunting ceases. When anatomic closure is achieved and cardiac anatomy is normal, shunting through ductus arteriosus also ceases.

  44.   C.   Hypothermia is defined as a body temperature less than 36°C. Prewarming for half an hour with convective forced-air warming blankets effectively prevents phase I (initial rapid decline in body temperature) hypothermia by eliminating the central-peripheral temperature gradient. Methods to minimize phase II hypothermia (slower decrease in body temperature) from heat loss include use of forced-air warming blankets and warm-water blankets, heated humidification of inspired gases, warming of intravenous fluids, and raising ambient operating room temperature. Passive insulators such as heated cotton blankets or the so-called space blankets have little utility in preventing hypothermia.

  45.   A.   Laryngospasm is a forceful and involuntary spasm of the laryngeal musculature caused by stimulation of the superior laryngeal nerve. Initial treatment of laryngospasm includes gentle positive-pressure ventilation with 100% oxygen and forward jaw thrust. Intramuscular or intravenous succinylcholine and controlled ventilation may be required in recalcitrant laryngospasm.

  46.   B.   Normal dead space in a neonate is 2 mL/kg.

  47.   B.   Approximately 70% to 80% of the hemoglobin at birth is fetal hemoglobin (HbF). The concentration of HbF decreases significantly by 3 to 6 months of age. HbF has a high affinity for oxygen, which shifts the oxyhemoglobin saturation curve to left. Sickle cell patients with more HbF have a better prognosis.

  48.   A.   Alveolar maturation is not complete until about 8 years of age. Increased airway resistance and decreased compliance lead to increased work of breathing and thus respiratory muscles easily fatigue. The chest wall collapses during inspiration, and residual lung volumes are low at expiration. The resulting decrease in FRC and increased oxygen consumption lead to rapid desaturation in the event of hypoxia. In addition, the hypoxic and hypercapnic ventilatory drives are not well developed in neonates and infants.

  49.   B.   Bupivacaine is cardiotoxic, and an inadvertent intravascular injection can lead to ST segment changes, cardiac arrhythmias, and cardiac arrest. When epinephrine is added to bupivacaine, tachycardia is usually seen, but at times this sign can be unreliable (higher heart rate in infants).

  50.   A.   Because of shorter circulation times than adults, all pediatric patients have a shorter onset time (up to 50% less) of muscle relaxants. Nonetheless, intravenous succinylcholine (1–1.5 mg/kg) has the fastest onset among muscle relaxants. Significantly larger volume of distribution is attributed to larger dose requirements in infants. With the notable exclusion of succinylcholine, mivacurium, and possibly cisatracurium, infants require significantly less muscle relaxant than older children. Moreover, based on weight, older children require higher doses than adults for some neuromuscular blocking agents (e.g., mivacurium and atracurium). As with adults, a more rapid intubation can be achieved with a muscle relaxant dose that is 1.5 to 2 times the ED95 dose at the expense of prolonging the duration of action.