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Miller > Ch 93 Pediatric Anesthesia > Flashcards

Ch 93 Pediatric Anesthesia Flashcards

1
Q

What constitutes a low birthweight infant

A

<2500g

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2
Q

What electrolyte abnormalities are seen in preterm infants

A

hypoglycemia
hypocalcemia
hypomagnesemia

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3
Q

What contributes to increased pulmonary blood flow after birth?

A
  • exposure of ductus arterioles to oxygenated blood causes it to close
  • effects of lung expansion
  • loss of low resistance through placental blood flow (increased peripheral resistance)
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4
Q

what is the mechanism of closure of the foramen ovale?

A

Increase in Left heart pressure (caused by increased peripheral vascular resistance)

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5
Q

Why does ductus arteriosis close? Why is patent DA seen more commonly in preterm infants?

A

Increased arterial oxygen concentration.

Arterial muscular tissue required for closure (not as available in preterm infants)

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6
Q

What is transitional circulation?

A

When the infant readily converts from adult to fetal circulation
-Causes rapid desaturation. Usually can improve with hyperventilation (decreased PaCO2 decreases pulmonary arterial pressure)

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7
Q

What are risk factors for prolonged transitional circulation?

A
  • prematurity
  • infection
  • acidosis
  • pulmonary disease resulting in hypercapnia or hypoxemia (e.g., meconium aspiration)
  • hypothermia
  • congenital heart disease
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8
Q

What are the physiological consequences of immature, less compliant myocardial structures in the neonate?

A
  • Tendency toward biventricular failure
  • sensitivity to volume loading
  • poor tolerance of increased afterload
  • HR dependent CO
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9
Q

Why is respiration less efficient in infants?

A

Smaller airways - more resistance
Highly compliant airways
Highly compliant chest wall, negative pressure poorly maintained (functional airway closure accompanies each breath due to these compliant states)
Immature diaphragmatic and intercostal muscles - easily fatigued

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10
Q

What are the 5 ways that infant airways differ from adults?

A
  1. large infant tongue - increased likelihood of obstruction and difficulties with laryngoscopy
  2. Higher (more cephalic) larynx
  3. Epiglottis is short, stubby, omega shaped and angled over larynx
  4. Angled vocal cords (a blind tube may be lodged in anterior commissure rather than slide into trachea)
  5. Funnel shaped larynx - narrowest at cricoid (may get caught up past cords)
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11
Q

Infants are obligate nasal breathers. Can they convert to oral breathing? When?

A

40% of term infants can covert to oral breathing if nasal airway obstructed (only 8% preterm)
By 5 months, almost all infants can easily convert to oral breathing.

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12
Q

When does kidney function completely mature?

A

2 years of age

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13
Q

Why is impaired glomerular and tubular function important in the neonate

A

Half life of medications prolonged (if they go through glomerular filtration)
Impaired ability to regulate large amounts of solutes and water

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14
Q

Why does the liver’s ability to metabolize medications improve as the infant grows?

A
  1. hepatic blood flow increases

2. Enzyme systems develop and are induced (Cytochrome P450)

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15
Q

How do plasma levels of albumin and other proteins compare in newborns versus infants? How does this effect pharmacology of drugs?

A

Newborns have lower plasma levels of albumin and other proteins necessary for drug binding than do infants.
Lower albumin levels results in less protein binding of some drugs –> greater levels of unbound drug

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16
Q

Are neonates at higher risk of GERD? Why?

A

Yes - ability to coordinate swallowing with respiration does not fully mature until 4-5months

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17
Q

Why are infants more vulnerable to hypothermia?

A

Thin skin, large ration of BSA to weight, limited ability to cope with cold stress (causes increased oxygen consumption and metabolic acidosis)

18
Q

What is the principal method of heat production in infants < 3 months?

A

Non-shivering thermogenesis - metabolism of brown fat

19
Q

Neonates have higher total body water content. How does this affect pharmacology?

A

Water soluble drugs have large volume of distribution, therefore requiring a larger initial dose (mg/kg) to achieve desired blood level. They also have delayed excretion secondary to larger VoDist.

20
Q

Neonates have less fat. How does this affect pharmacology?

A

Drugs that depend on redistribution into fat for termination of action will have a long clinical effect. This is similar for drugs that redistribute into muscles.

21
Q

How is does half life of most medications compare in older children to adults? Why

A
  • Half life is shorter or equivalent to that of adults
  • larger fraction of CO diverted to liver and kidneys (weight more in relation to body weight)
  • mature renal and hepatic function
22
Q

Why is uptake of volatiles more rapid in children?

A

Increased RR, cardiac index, and greater proportional distribution of cardiac output to vessel-rich organs

23
Q

What is the MAC value for sevoflurane for neonates, infants (1-6months) and children >6 months?

A

Neonates: 3.3%
Infants: 3.2%
Children: 2.5%

24
Q

How does sevoflurane affect RR and TV?

A

Decreases both

25
Q

How does sevoflurane affect hemodynamics (HR, BP)? How does this compare with halothane?

A

For children >3 yo
Sevo: increase in HR, no change in SBP
Halothane: no change in HR, SBP decreases

26
Q

At what age group is emergence delirium most common?

A

5 years or younger

27
Q

What 2 volatile agents are recommended for gaseous inductions in children and why?

A

Halothane and sevoflurane

  • airway related problems occurs frequently
  • less noxious
28
Q

Between sevoflurane and halothane, which is more of a myocardial depressent

A

Halothane

29
Q

What are the MAC values for desflurane for:

  • neonates
  • infants 1-6 month
  • infants 6-12 months
  • 1-3 years
  • 5-12 years
A 
Neonates: 9.2%
Infants (1-6mo): 9.4%
Infants (6-12mo): 9.9%
1-3 years: 8.7%
5-12 years: 8%
30
Q

Which genetic defect puts children at risk for PRIS?

A

Mitochondrial disease - specifically those with defects in lipid metabolism

31
Q

What are the contraindications to ketamine in children? (2015)

A

Upper respiratory tract infection
Increased ICP
Open globe injury
Psychiatric or sz disorder

32
Q

What is the dose of etomidate?

A

0.2-0.3mg/kg

33
Q

How is diazepam metabolized?

A

hepatically

34
Q

What is the elimination half life of midazolam? What is it in neonates?

A

2 hours in children; 6-12 hours in neonates

35
Q

What drug class is dexmedetomidine?

A

selective alpha2-adrenergic agonist

36
Q

What is the dose of dexmeditomide (bolus and infusion?)

A

Initial dose: 0.7-1ug/kg over 10 minutes,

Infusion: 0.5-1 ug/kg/h

37
Q

Why might the neonate be more sensitive to morphine

A

More permeable blood brain barrier, but most likely related to pharmacodynamics

38
Q

What is the time to a 50% reduction in effect-site concentration (i.e., effect on resp rate) for remifentanil?

A

4 minutes

39
Q

What is the difference (if any) in remifentanil’s half life in adults, infants and neonates?

A

Minimal difference due to degradation by nonspecific plasma and tissue esterase’s

40
Q

What is the dose for IV Sux in infants and why is it higher than for older children?

A

2 mg/kg

-highly water soluble and rapidly redistributes

41
Q

What is the IM dose of sux in infants <6 months, and older children? How long will muscle relaxation last via this route?

A

Infants: 5mg/kg IM
Children >6 months: 4 mg/kg
May last 20 minutes

42
Q

What is the approximate blood volume in a preterm infant, term infant, child 3-12 months, child over 1 year?

A

Preterm: 100-120mL/kg
Term: 90 mL/kg
3-12 months: 70-80mL/kg
>1 year: 70mL/kg

Miller (5 decks)

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