Pediatric Anesthesia Flashcards
Is the oxyhemoglobin dissociation curve of the newborn shifted to the left or the right? Why?
It is shifted to the left because fetal Hgb which consists of two alpha and two gamma chains instead of two alpha and two beta chains (adult HgB) is unable to bind 2,3-DPG and therefore has a higher affinity for oxygen.
By what age is fetal Hgb replaced by adult Hgb?
4-6 months of age in full-term infants. This can be delayed until up to 12 months for the preterm infant.
At what conceptual age is surfactant developed?
It begins at 22-26 weeks gestation, peaking at 35-36 weeks.
What intrapleural pressure is generated during the first breath of neonatal life?
The first breath of neonatal life is a gasp that generates a transpulmonary distending pressure of 40-80 cmH2O, in other words
The adult lungs comprise from 300 million to 480 million alveoli; how many alveoli comprise the neonatal lungs?
About 30 million alveoli which is approximately 1/10th the number in the adult lungs. Most alveoli are formed by 18 months but maturation continues until about 8 years of age.
Identify the two limitations of kidney function in the newborn. What is the significance of these limitations?
Neonates are obligate sodium excreters due to immature renal tubules. Therefore, the ability to concentrate urine is impaired. GFR is also diminished. Thus, infants do not tolerate large volumes of water and salts.
When do liver enzymes become completely functional in the neonate?
The cytochrome P450 enzyme system is fully functional at 1 month of age.
Where does the spinal cord end in the neonate?
Approximately L3 and it does not reach the adult location of L1 until 1 year of age.
How do chest wall compliance and pulmonary lung compliance differ in the neonate compared with the young, healthy adult?
Chest wall compliance is increased and pulmonary compliance is decreased.
In newborns, the closing capacity is greater than the FRC. What is the physiologic complication?
Small airway closure occurs during tidal volume breathing and thus there is less oxygen reserve in the FRC.
What is the length of the infant trachea from the cords to the carina in centimeters?
It varies from 5-9 cm in infants and neonates and children up to 1 year of age.
List 5 ways the neonatal airway differs from the adult airway and one anesthetic implication for each.
1) Larynx is more cephalad (C1-C2) 2) –> straight blade more useful than curved blade; 2) epiglottis is stubby, short, and omega-shaped –> control with laryngoscopy blade is more difficult; 3) tongue is larger –> increased risk for airway obstruction and may be difficult to displace with laryngoscopy; 4) vocal cords angled anteriorly –> ET tube may lodge in anterior commissure rather than slide into trachea; 5) larynx is funnel-shaped with the narrowest portion occurring at cricoid cartilage –> may be difficult to pass ET tube, may require smaller tube.
At what age do the pediatric laryngeal cartilages reach adult proportions?
At age 10-12 years.
What is the estimated blood volume of the preterm neonate (in mL/kg)? Of the neonate? of an infant 3 months to 3 years?
Preterm neonate: 90-100 mL/kg. Term neonate: 80-90 mL/kg. 3 months-3 years: 75-80 mL/kg.
Describe the physiological anemia of the neonate and pediatric patient.
Normal hemoglobin levels in the full-term infant range from 14-20 g/dL. It progressively declines during the 9-12th week reaching a minimum of 10-11 g/dL with a hematocrit of 33%. After the 3rd months, hemoglobin levels stabilize at 1.5-12 g/dL until about 2 years of age then gradually increase to adult levels of 14-15.5 g/dL by puberty.
Below what hemoglobin concentration is anemia sufficient to jeopardize oxygen carrying capacity in the neonate? Infant older than 3 months?
Hgb concentrations < 13 g/dL in the newborn and less than 10 g/dL in the pediatric patient older than 3 months jeopardizes oxygen-carrying capacity.
A 3 month old infant, who is scheduled for surgery has a hemoglobin concentration of 10.5 g/dL. What action should be taken?
Nothing, this hemoglobin level is normal for this age.
Why is cardiac output in infants dependent on HR and not stroke volume?
Because ventricular compliance is decreased which results in limited ability to increase myocardial contractility and stroke volume so the only way to alter cardiac output is to change heart rate.
At what rate do infants consume oxygen? How does this compare to the adult?
Resting O2 consumption is about 6-8 mL/kg/min which is twice that of the adult.
By what route do infants lost most of their body heat?
Most heat loss is by radiation (this applies to any age)
Newborns produce heat primarily by what mechanism?
Non-shivering thermogenesis by metabolism of brown fat.
What is the significance of brown fat? Where is brown fat located?
Infants respond to cold stress by increasing norepinephrine production which enhances metabolism of brown fat and increases body heat. Brown fat is located in the interscapular space and around large blood vessels, around the neck, the axilla, behind the sternum, and around the kidneys and adrenals.
What controls non-shivering thermogenesis in infants?
The sympathetic nervous system activates NST in infants. Specifically, norepinephrine and thyroid hormone stimulate triglyceride and fatty acid metabolism of brown fat stores.
At approximately what age does non-shivering thermogenesis cease to be clinically significant?
At about 2 years of age.
