Pediatric Anesthesia Flashcards
What is considered pre-term?
Prior to 37 weeks gestational age
What is considered neonate?
1-28 days of life
Which direction does fetal Hgb shift the oxyhemoglobin dissociation curve?
Left (increased O2 loading in the lungs/placenta, decreased O2 unloading at tissues)
What is Hgb of full term neonate?
18-20g/dl
At what fetal age are primitive lung buds developed from the foregut?
4 weeks
At what fetal age is branching of bronchial tree complete to 28 divisions, no further formation of cartilaginous ariways?
16 weeks
At what age are primitive alveoli and type II cells present; surfactant detectable; survival possible with artificial ventilation?
24 weeks
What is guppy breathing?
Fetus makes respiratory movements in utero from 30 weeks gestation at a rate of 60/min
What is the current view on adaptation of breathing?
Rhythmic breathing occurs with clamping of the umbilical cord and increasing O2 tensions from air breathing
What is the primary event of the respiratory system transition?
Initiation of ventilation
With onset of ventilation, what happens to PVR and pulmonary blood floor?
PVR decreases dramatically and pulmonary blood flow increases
Since neonate and infant lungs are prone to collapse, what can be done to prevent this?
PEEP
Why are neonate and infant lungs prone to collapsing?
- Weak elastic recoil
- Weak intercostal muscles
- Intra-thoracic airways collapse during exhalation
How do infant’s lungs not collapse all the time?
Infants terminate the expiratory phase of breathing before reaching their true FRC which results in intrinsic PEEP and higher FRC
What is the most common and universal sign of respiratory distress in the infant?
Tachypnea
What two things can abolish the neonates initial hyperpneic response to hypoxia?
Hypothermia and low levels of anesthetic gases
What are the two phases of response to hypoxia in the neonate?
Initial response is hyperpnea. Secondary response in about two minutes is respiratory depression and apnea.
What does hypoxia cause in babies?
PROFOUND bradycardia
What are 6 contributing factors for apnea of infancy?
- Fatigue from prolonged increased WOB.
- Inefficient diaphragmatic contraction
- 25% of muscle fibers in diaphragm are Type 1 fatigue resistant (adults have 55%) work horse fibers
- increased O2 Consumption
- Decreased FRC
- Increased closing volume.
In utero, how much CO goes to lungs?
5-10%
How much blood is diverted away from the liver via the ductus venosus?
50%
What two things cause the PDA to close?
Increase in PO2 and decrease in circulating prostaglandins
When is physiologic closue/anatomic closure of PDA?
10-15 hours
2-3 weeks.
Does a R-L shunt or L-R shunt re-open the PFO?
R-L shunt
T/F: Before anatomic closure of the fetal shunts, nothing will cause them to open?
False; Right to left shunting may occur in normal neonates during coughing, bucking, straining
What is treatment for PPHTN?
Hyperventilation to maintain alkalosis Pulmonary vasodilators Minimal handling Avoidance of stress Adequate ventilation and oxygenation is key
Fetal kidneys have higher or lower RBF and GFR?
Lower
Why is fetal GFR/RBF lower?
- Structurally immature small size and number of glomeruli
- Low systemic arterial pressure
- High renal vascular resistance
- Low permeability of glomerular capillaries
How many weeks is considered “Full term” ?
37 weeks
T/F: Neonates have matured neontal renal tubules but not a normal RAAS?
False; normal RAAS but abnormal renal tubules
What does abnormal renal tubules lead to?
Inadequate sodium conservation
T/F: Neonate is considered an “obligate sodium conserver”?
False; “obligate sodium loser”
T/F: NS infusion in a neonate will result in dehydration
True
Which method of heat loss is greatest?
Radiation
What two methods can prevent radiation heat loss?
- Warm operating rooms
2. Radiant lamp “french fry lights”
Heat production is achieved by what three things?
- Voluntary muscle activity
- Involuntary muscle activity
- Non-shivering thermogenesis.
What is non-shivering thermogenesis?
Metabolism of brown fat which develops in the fetus b/t 26-30 weeks gestation. This comprises 2-6% of neonates total body weight.
Where is brown fat located in the neonate?
Mediastinum b/t the scapulae, around the adrenals, and in the axilla.
How is non-shivering thermogensis mediated?
Sympathetic nervous system.
The heat produced with non-shivering thermogenesis is a product of what?
Fatty acid metabolism.
