Topics in Pediatric Physiology

Question 1

What is atelectasis?

Answer 1

complete or partial collapse of lung or section of lung

Question 2

What is tachypnea?

Answer 2

abnormally rapid breathing

Question 3

What is subglottic stenosis?

Answer 3

• narrowing of the airway below the vocal cords (subglottis) and above the trachea - involve narrowing of the cricoid - often caused by scarring in the larynx just below the vocal cords

Question 4

What happens to the diaphragm when a patient is placed in supine position?

Answer 4

1) gastric organ pressure on the diaphragm
- recommended 20 to 30 degree head up position to prevent such pressure and minimize risk of regurgitation and aspiration

Question 5

Compared to adults, children have ________ rate of of alveolar ventilation (AV) per unit area

Answer 5

increased, because they have a greater proportion of alveolar surface to lung size

proportionally greater exchange of gas across the alveoli

Question 6

Total volume of gas exchanged in children is ____ than adults. Functional residual capacity is ______ in children than it is in adults

Answer 6

less, less

FRC: volume of gas remaining in the lungs at the end of a normal expiration

Question 7

What ratio helps determine the rate at which changes in inspired gas concentration affect a clinical response?

Answer 7

AV/FRC

AV: Alveolar ventilation

FRC: Free residual capacity

AV supports transport of inhaled gas through the bloodstream and to the brain; FRC determines how much gas remains in the lungs during normal breathing

As ratio increases, body reacts more quickly to changes in inhaled gas concentrations

Question 8

What is the average heart rate of a newborn?

Answer 8

120-170 beats per minute

Question 9

What is the average blood pressure of a 6 year old boy?

Answer 9

110/70

Question 10

What is the average blood pressure of a 3 year old female?

Answer 10

103/62

Question 11

What is the average heart rate of a 3 year old?

Answer 11

80-120 beats per minute

Question 12

What is the average heart rate of a 6 year old?

Answer 12

75-115

Question 13

What is the formula for cardiac outpout (CO)?

Answer 13

CO=SV x HR

SV doesn’t change beacuse the infant heart is relatively inelastic and cannot make rapid changes in stroke volume

Question 14

Sympthatic/Parasympathetic tone is more marked in immature nervous system. What does this mean?

Answer 14

Parasympathetic. more prone to significant bradycardias with vagal stimulation

Question 15

What is often given to children undergoing manipulation of the airway such as intubation to prevent vagally induced bradycardia?

Answer 15

atropine - antimuscarinic/anticholinergic that inhibits parasympathetic system

treats slow heart rate and decreases saliva production during surgery

Question 16

A decrease in cardio output causes ________ in the rate of inhaled anesthetic uptake

Answer 16

increase

40% of child’s cardiac output perfuses the brain

Question 17

Infants and young children have _______________ acidity in their GI system

Answer 17

Decreased

adult levels not reached until 2 to 2.5 years of age. low acidity favors absorption of weakly acidic drugs like penicillins and cephalosporins, whereas the absorption of weakly basic drugs such as benzodiazepines is delayed

Question 18

Infant GI system shows _____ gastric emptying times

Answer 18

increased

results in slower gastric drug absorption

Question 19

Lower levels of which enzyme in the first 2 months of life are associated with sluggish oxidation of diazepam, phenytoin, and phenobarbital in neonate?

Answer 19

cytochrome p450 enzyme, children relatively deficient in liver enzymes responsible fo metabolizing, detoxifying, or altering a drug

Question 20

What is deficient in neonates that makes drugs such as morphine, acetaminophen, steroids, and sulfa antibiotics unsafe?

Answer 20

glucuronyltransferase - conjugates drugs into excretable form

Question 21

Deficiency in which enzyme in infant liver causes an exaggeration of the effects of succinylcholine?

Answer 21

pseudocholinesterase - infants could respond with prolonged apnea; deaths have been reported in associated with undiagnosed myopathies

Question 22

What is glomerular filtration rate (GFR) and why is it important in newborns?

Answer 22

volume of fluid filtered by the kidney per unit of time; participates in excretion of drugs such as penicillins, short-acting barbiturates and phenobarbital; dosages of agents must be calculated to consider low infant GFR

Question 23

What is tubular transport and why is it important in infants?

Answer 23

group of mechanisms that transfer drug and drug metabolites across renal tubular epithelium; morphine, atropine, sulfa antibiotics; decreased tubular transport rates in young infants and thus have narrower margins of toxicity