Pediatric Anesthesia - Quiz 1 Flashcards
What is the age of a Neonate?
1 - 28 days of life
What is the age of an Infant vs Child?
Infant: 28 days - 1 yr
Child: > 1 yr
When does the most significant part of transition occur for a newborn?
24 -72 hrs after birth
What are the adaptive changes for a Newborn?
Establish FRC
Convert Circulation
Recover from Asphyxia
Maintain Core Temp
Where does Gas Exchange occur in regards to Fetal Respiration?
Placenta
How is the majority of O2 Transport accomplished by the Fetus?
Left Fetal Hgb Shift
What happens to O2 Unloading after birth?
Becomes Insufficient
What is the normal Hgb for a full term Neonate?
18 - 20 g/dL
How developed is the Fetal Lung at 4 weeks?
Lung Buds develop from Foregut
At what week of gestation does the Fetal Lung have Complete branching of the Bronchial Tree to 28 Divisions?
16 Weeks - no more cartilaginous airway formation
When does the Fetal Lung have Alveoli & Type II Cells w/ Surfacant?
24 Weeks
What happens w/ Fetal Lung Development at 28-30 weeks?
Capillary Network surrounds Saccules & baby can survive w/o support
When does the Fetal Lung have true Alveoli present?
36 - 40 weeks - about 20 million @ birth
What happens in Fetal Lung Development at Birth to 3 months?
PaO2 rises as R-to-L mechanical shunts close
What happens to the number of Alveoli present once the the child reaches 6 years of age?
Rapid increase to 350 million Alveoli
When does the Fetus start to “Guppy Breathe” in Utero?
30 weeks at a rate of 60 breaths/min
Prenatal Respiratory Practice
What happens in utero that could cause Lung Hypoplasia?
Denervation or damage to the Diaphragm
How does the Carotid, Aortic, and Peripheral Chemoreceptors play a role in Fetal Breathing?
Does NOT alter fetal breathing or Initation of Ventilation at birth
What initiates in utero Rhythmic Breathing?
Clamping of Umbilical Cord & Increasing O2 Tension from Air Breathing
What augments and maintains continuous rhythmic breathing?
Hyperoxia w/ Air Breathing & Low Fetal PaO2
Continuous breathing does NOT depend on PaCO2
What depresses or abolishes continuous breathing?
Hypoxia
What happens to the Fetal Lungs w/ onset of Ventilation?
↓Pulm. Vascular Resistance d/t ↑PO2 & ↓PCO2
&
↑Pulm. Blood Flow
The primary event of Respiratory transition is the Initiation of Ventilation. How do Alveoli change at this point?
Fluid-filled Alveoli to Air-Filled
What helps overcome the Large Surface Tension forces in the Newborn’s Lungs?
Small Radius of the Diaphragm’s Curve
&
High Negative Pressure of -70 cm H2O generated by the baby
What is the FRC for a Newborn?
25 - 30 mL/kg - buffer for PO2 & PCO2 changes b/t breaths
Neonates have weak elastic recoil and intercostal muscles, making them prone to what?
Lung and Intra-Thoracic Airway Collapse during Exhalation
What happens when Closing Volumes are equal or above the FRC?
Small airway closure
Lung Collapse
V/Q Mismatch
What is unique about how the infant’s lungs work that prevents their lungs from collapsing all the time?
Infants end their expiratory phase early
This creates PEEP & a higher FRC
Anesthesia inhibits this function
Do neonates have respiratory control in response to hypercarbia?
Yes, but the control is still immature. They will hyperventilate, but the slope of response is decreased
What depresses the Neonate’s response to CO2?
Hypoxia
What are the 2 phases of the Neonate’s response to Hypoxia?
First Phase: Hyperpnea
Second Phase: Depressed Respirations after 2 min.
What abolishes the Neonate’s Hyperpnea response to Hypoxia?
Hypothermia & Anesthetic Gas
How does Hypoxia affect the baby’s heart rate?
Profound Bradycardia
What is Apnea of Infancy?
Respiratory pause > 20 sec or w/ Bradycardia or Cyanosis
What factors contribute to Apnea of Infancy?
↑Work of Breathing
↑O2 Consumption & Closing Volume
Compliant Upper Airway & Ribs = Easy Collapse
Inefficient Diaphragmatic Contraction
Only 25% Type 1 Diaphragm Muscles
(vs. 55% in Adults)
↓FRC
Why do Fetal Intracardiac & Extracardiac Shunts Exist?
To Minimize blood flow to Lungs & Maximize flow to Organs
What are the Fetal Shunts that develop in birth?
Ductus Venosus
Foramen Ovale
Ductus Arteriosus
How does Fetal Blood circulate?
Deoxygenated blood –> Descending Aorta –> Umbilical Arteries –> Placenta –> Oxygenated Blood –> Umbilical Vein –> 50% to Liver / 50% to Ductus Venosus –> IVC –> RA –> RV –> Ductus Arteriosus –> PA & Aorta
The Umbical Arteries to the Placenta have very _____ resistance to blood flow
The Umbical Arteries to the Placenta have very Low resistance to blood flow
What is the PO2 of the Oxygenated blood that returns via the Umbilical Vein?
35 mmHg
With Fetal Circulation, the Pulmonary Vascular Resistance is very _____ & the SVR is very ______
With Fetal Circulation, the Pulmonary Vascular Resistance is very High & the SVR is very Low
What is the PO2 of the Blood entering the Descending Aorta that then goes to the Placenta?
22 mmHg
In Fetal Circulation, which pathway does O2 rich blood go directly from the Right Atrium to the Left Atrium?
Foramen Ovale
What happens during the Transitional Fetal Circulation when the Umbilcal Cord is cut?
↑SVR
Reversal of Shunts
Breathing Starts
↓Pulm. Vascular Resistance
↑LA Pressure
↓RA Pressure
Foramen Ovale Closes
What happens to Pulmonary Blood Flow when Fetal Ventilation first starts?
450% Increase in Pulm Blood Flow
During Transitional Circulation, how does increased PO2 affect the Ductus Arteriosus?
Constricts w/in Minutes and Circulating Prostaglandins decrease
How long does it take for the Ductus Arteriosus to close?
Physiologic: 10 -15 hrs
Anatomic: 2-3 wks
What causes Persistent Pulmonary Hypertension of the Newborn (PPHN)?
Persistent Fetal Shunting after Transition Period
Hypoxia
Acidosis
What can cause the Reopening of The Foramen Ovale?
Persistent Pulmonary Hypertension in the Neonate
&
Cold Stress
What are the symptoms of PPHN?
Cyanosis
Tachypnea
Acidosis
R-to-L Shunt across FO & DA
What causes the normal condition of Transient R-to-L shunting before anatomical ductus closure?
When baby coughs, bucks, or strains during induction or emergence
How is PPHN treated?
Hyperventilation
Pulmonary Vasodilators - Prostaglandin
Minimal Handling
Avoid Stress
What is the major function of the Fetal Renal System?
Passive Urine formation contributing to Amniotic fluid
Fetal kidneys have ____ Renal Blood Flow & GFR
Fetal kidneys have Low Renal Blood Flow & GFR
What happens to the Renal System during the Transitional Stage?
↑SVR
↓Renal Vascular Resistance
↑Kidney Size & Fxn
At what gestational period are all fetal nephrons developed?
34 weeks
What is the Urine Osmolarity of a Neonate at birth?
700 - 800 mOsm/L
What is the Creatnine of a Neonate at birth?
0.8 - 1.2 mg/dL
Why does the Neonate have trouble Concentrating Urine?
Inadequate Sodium Conservation
Neonates have normal Renin-Angiotensin System, but immature Tubules
The baby is an “Obligate Sodium Loser”
What is the Normal Urine Sodium in an Adult vs Baby?
Adult: 5-10 mEq/L
Neonate: 20-25 mEq/L
What is an important point in regards to fluid management in the Neonate?
Fluids must contain Sodium
Ideal Fluid: D5 0.2% NS
Why is a Hematocrit of 35% the lowest acceptable for the Neonate?
High O2 Demand
Limited ability to Increase CO
Increased Blood Volume & CO per weight
What is the Blood volume for a Term Baby vs. a Pre-Term Baby?
Term: 90mL/kg
Pre-Term: 100mL/kg
Why are Neonates more susceptible to heat loss?
Small Size
Increased Surface Area
Increased Thermal Conductance
How does the Neonate produce heat?
Voluntary/Involuntary Muscle Activity
&
Non-Shivering Thermogenesis
How does Non-Shivering Thermogenesis work?
Metabolism of Brown Fat located in the Mediastinum b/t the Scapulae & around the Adrenals in the Axilla
What mediates Non-Shivering Thermogenesis?
Sympathetic Nervous System
