Neonates Part I Flashcards
1
Q
Define the neonatal period.
A
- First 28 days of extrauterine life.
2
Q
Why might anesthesia be required for neonates?
A
- Life-threatening illness.
- Medical conditions needing surgical intervention.
3
Q
What types of surgical interventions might neonates need anesthesia for?
A
- Palliative
- Staged
- Corrective
4
Q
Why is the neonate particularly vulnerable during the neonatal period?
A
- Vulnerable to internal and external stressors.
5
Q
How should the anesthetic plan for neonates be tailored?
A
- To mitigate physiologic stress
- Improves neonatal morbidity and mortality.
6
Q
What does anesthetic management of neonates require?
A
- Specialized knowledge about patients
- Extreme vigilance
- Refinement of technical skills.
7
Q
Does anesthetic management differ between term and premature neonates?
A
- Requires integration of specialized knowledge for both term and premature neonates.
8
Q
How does fetal circulation’s organ of respiration differ from the adult’s?
A
- Fetal: Placenta
- Adult: Lungs
9
Q
How is fetal circulation arranged compared to adult circulation?
A
- Fetal: In parallel
- Adult: In series
10
Q
What shunting occurs in fetal circulation?
A
- Right-to-left shunting across the foramen ovale and ductus arteriosus.
11
Q
Compare the Systemic Vascular Resistance (SVR) between fetal and adult circulation.
A
- Fetal: SVR is low
- Adult: SVR is higher.
12
Q
Compare the Pulmonary Vascular Resistance (PVR) between fetal and adult circulation.
A
- Fetal: PVR is high
- Adult: PVR is lower
13
Q
Describe the pulmonary blood flow and left atrial pressure in fetal circulation.
A
- Minimal pulmonary blood flow
- Low left atrial pressure.
14
Q
What is the purpose of the ductus venosus in fetal circulation?
A
- Shunts blood from the umbilical vein to the IVC (bypasses liver).
15
Q
What role does the foramen ovale play in fetal circulation?
A
- Shunts blood from the RA to the LA (bypasses lungs).
16
Q
What is the function of the ductus arteriosus in fetal circulation?
A
- Shunts blood from the pulmonary artery to the aorta (bypasses lungs).
17
Q
How many umbilical veins are there and what is their function?
A
- One umbilical vein
- Carries oxygenated blood from the mother to the fetus.
18
Q
How many umbilical arteries are there and what is their function?
A
- Two umbilical arteries
- Carry deoxygenated blood from the fetus to the mother.
19
Q
Why can fetal shunts be problematic during extrauterine life?
A
- Beneficial in-utero
- Problematic if remain open during extrauterine life.
20
Q
What is the function of the one umbilical vein in fetal circulation?
A
- Provides oxygen-rich blood to the fetus.
21
Q
How does the ductus venosus contribute to fetal circulation?
A
- Shunts oxygenated blood past the liver
- Saving oxygen for the heart and brain.
22
Q
Describe the mixing of blood in the inferior vena cava (IVC) in fetal circulation.
A
- Oxygenated blood from the ductus venosus and deoxygenated blood from the lower body converge, creating two streams of blood at different rates.
23
Q
What is the significance of the higher velocity of oxygenated blood in the fetal heart?
A
- Enters the RA and
- Is preferentially diverted across the foramen ovale to the LA
- Perfusing the myocardium and brain.
24
Q
How is deoxygenated blood directed in fetal circulation?
A
- Lower velocity blood is directed to the RV and pulmonary trunk
- then shunted via the ductus arteriosus to the descending aorta
- perfusing the lower body and returning to the placenta through two umbilical arteries.
25
What causes shunting between the pulmonary and systemic circulations?
- Abnormal communication between the pulmonary and systemic circulations.
26
What factors determine the size and direction of a shunt?
- Ratio of PVR to SVR
- Pressure gradients between cardiac chambers or arteries
- Compliances of the cardiac chambers.
27
What happens when PVR is greater than SVR?
- Right-to-left (R → L) shunt occurs.
28
What happens when SVR is greater than PVR?
- Left-to-right (L → R) shunt occurs.
29
What is a cyanotic shunt and give an example?
- Cyanotic shunt (R → L): Tetralogy of Fallot.
30
What is an acyanotic shunt and give an example?
- Acyanotic shunt (L → R): Ventricular septal defect.
31
How does a right-to-left shunt affect anesthesia induction?
- Slower inhalation induction
- Faster IV induction.
32
How does a left-to-right shunt affect anesthesia induction?
- Negligible effect on inhalation induction rate.
- Possibly prolongs IV induction onset.
33
What is Eisenmenger syndrome?
- A left-to-right shunt changes to a right-to-left shunt due to pulmonary hypertension.
34
What is a Cyanotic Shunt (R → L) also known as?
- Known as "Blue Baby."
35
What happens in a cyanotic shunt?
- Blood bypasses the pulmonary circulation.
36
Why does the blood appear blue in a cyanotic shunt?
- Shunted blood does not bind oxygen in the lungs
- Diluting the final PO2 of blood ejected by the left ventricle.
37
What is an Acyanotic Shunt (L → R) also known as?
- Known as "Pink Baby."
38
What occurs in an acyanotic shunt?
- Oxygenated pulmonary venous blood is recirculated through the right heart and lungs
- Instead of being pumped to the body.
39
What are the consequences of an acyanotic shunt?
- Robs the body of blood flow.
- Overloads the right heart and pulmonary vasculature.
40
What determines cardiac output in neonates?
- Heart rate.
41
How do neonates' oxygen consumption and CO2 production compare to adults?
- Twice as much per weight.
42
What's more efficient for neonates, increasing respiratory rate or tidal volume?
- Increasing respiratory rate.
43
Is stroke volume fixed or variable in neonates?
- Fixed.
44
How does the neonate's left ventricle respond to increased afterload?
- By increasing heart rate.
45
Which part of the autonomic nervous system is less mature in neonates?
- Sympathetic nervous system (SNS).
46
How do neonates respond to laryngoscopy?
- With bradycardia.
47
What risk does pain pose in neonates?
- Predisposes to intracerebral hemorrhage.
48
Up to what age do infants prefer nose breathing?
- Up to 5 months.
49
How does the size of the tongue in infants compare to their mouth volume?
- Larger tongue relative to mouth volume.
50
Describe the neck length in pediatric patients.
- Shorter neck.
51
What is the shape and characteristics of the epiglottis in infants?
- U or omega shape
- Longer and stiffer
52
How do vocal cords in infants differ from adults?
- Anterior slant.
53
Where does the laryngeal position correspond in infants?
- C3 - C4.
54
What is the narrowest fixed region in the pediatric airway?
- Cricoid ring.
55
What is the narrowest dynamic region in the pediatric airway?
- Vocal cords.
56
Describe the shape of the subglottic airway in infants.
- Resembles a funnel.
57
How does the position of the right mainstem bronchus in infants compare to adults?
- Less vertical
- Takes off 55 degrees from midline.
58
Neonates' oxygen consumption rate?
- 6 mL/kg/min.
59
Neonates' alveolar ventilation compared to adults?
- Increased.
60
Neonates' FRC level?
- Slightly decreased.
61
Result of neonates' hypoventilation/apnea?
- Rapid desaturation.
62
Effect of FRC turnover on anesthetic induction in neonates?
- Faster inhalation induction.
63
What is the primary muscle of inspiration?
- Diaphragm.
64
How do intercostal muscles contribute to ventilation in neonates?
- Very little due to inadequate development.
65
How does the position of the ribs affect thoracic volume in neonates?
- Less able to augment due to more horizontal position.
66
What types of muscle fibers compose the diaphragm and intercostal muscles?
- **Type 1**: Slow-twitch, endurance, fatigue-resistant
- **Type 2**: Fast-twitch, short bursts, tires easily.
67
Percentage of type 1 fibers in the neonatal diaphragm?
- 25% (Adults have 55%).
68
How does the composition of muscle fibers in the neonate's diaphragm affect respiratory function?
- Reduced ventilatory reserve due to fewer type 1 fibers.
69
Risk associated with fewer type 1 fibers in the neonate's diaphragm?
- Increased risk for respiratory fatigue and failure.
70
How does lung compliance in newborns compare to adults?
- Lower lung compliance.
71
What is the chest wall compliance in newborns?
- Higher
- Leading to potential chest wall collapse during inspiration.
72
How do neonatal lung volumes compare to adults?
- Smaller FRC, vital capacity
- Total lung capacity
- Greater residual volume, closing capacity
- Similar tidal volume
73
What challenges do neonates face during inspiration?
- Must overcome airflow resistance and elastic properties of chest wall and lungs.
74
What impact do minor reductions in airway diameter have on neonates?
- Significantly increases work of breathing.
75
What is unique about fetal circulation?
- **Umbilical vein** supplies oxygen
- **Umbilical arteries** return CO2-rich blood.
76
What stimulates a newborn to breathe rhythmically?
- Clamping the umbilical cord.
77
How does PaO2 level affect neonatal breathing?
- Acute rise promotes continuous breathing
- Hypoxemia causes apnea
78
What is the neonate's pH at birth and 1 hour after delivery?
- Birth: pH = 7.20
- Stabilizes to 7.35 after 1 hour.
79
When does respiratory control mature in neonates?
- Between 42 - 44 weeks post-conceptional age.
80
How does hypoxemia affect neonates before respiratory control matures?
- Inhibits ventilation.
81
What is the P50 value of fetal hemoglobin (Hgb F)?
- 19 mmHg.
82
How does Hgb F affect the oxygen dissociation curve?
- Shifts the curve to the left (left = love).
83
Why is the left shift of Hgb F beneficial for the fetus?
- Facilitates O2 passage from mother to fetus
- By creating an oxygen partial pressure gradient across the uteroplacental membrane.
84
How does the CNS in newborns differ from older children?
- Less myelination
- Different muscle tone Reflexes
- Underdeveloped cerebral cortex.
85
When is myelination of the nervous system complete?
- By age 3.
86
How does the neuromuscular junction change in the first 2 months of life?
- Undergoes developmental changes.
87
Are pain pathways and receptors present at birth?
- Yes, present within the CNS.
88
Signs of pain in preverbal patients include?
- Tachycardia
- Elevated BP
- Crying
- Restlessness
- Grimacing
89
Why is increased BP dangerous in newborns, especially preemies?
- Lack of cerebral vascular autoregulation can lead to intracerebral bleeding.
90
How quickly does the brain grow in the first year of life?
- Doubles in weight in the first 6 months
- Triples by 1 year
91
When do the major fontanelles close in neonates?
- Anterior by 2 years
- Posterior by approximately 4 months.
92
What can the anterior fontanelle indicate in newborns?
- Increased intracranial pressure
- Dehydration.
93
At what age does the blood-brain barrier mature?
- Approximately 1 year of age.
94
What migration occurs in the conus medullaris and dural sac with pediatric growth?
Migrate cephalad.
95
Where is the conus medullaris in neonates?
Between L2 and L3.
96
Where does the dural sac end until 6 years of age?
Between S2 and S3.
97
At what age is the spinal cord position similar to an adult?
Age 8.
98
How does the neonatal kidney compare to the adult kidney at birth?
* Immature with decreased perfusion pressure
* Decrease glomerular filtration rate
* Decrease diluting and concentrating ability.
99
Why are neonates intolerant of fluid restriction?
Poor water conservation.
100
What is the neonate's ability regarding fluid overload?
Unable to excrete large volumes of water.
101
What is the most significant source of water loss in neonates?
Evaporation from high insensible losses.
102
How do neonates handle sodium in the first few days of life?
Obligate sodium loser.
103
When do neonates improve in retaining sodium?
After the first few days, better at retaining than excreting sodium.
104
When does GFR reach adult levels in neonates?
8 - 24 months of age.
105
When does renal tubular function achieve full concentrating ability?
~ 2 years of age.
106
What is the total body water status in premature newborns?
* Highest in premature newborns
* Decreases with age.
107
How does total body water (TBW) change with age?
* Highest at birth
* Decreases with age.
108
How does extracellular fluid (ECF) change with age?
* Highest at birth
* Decreases with age
109
How does intracellular fluid (ICF) change with age?
* Lowest at birth
* Increases with age
110
What are signs of dehydration in infants?
* Sunken anterior fontanel
* Weight loss
* Lethargy
* Dry mucus membranes
* Increased hematocrit
111
When does total body water as a function of weight reach adult values?
By one year of age.
112
What is the basis of fluid management in neonates?
* The 4:2:1 rule
* Consisting of hourly maintenance
* NPO deficit
* Third-space loss
* Blood loss.
113
How much fluid does a baby require after the first week?
150 mL/kg/day.
114
When is the routine use of glucose-containing solutions recommended for neonates?
Only if the neonate is at risk for hypoglycemia.
115
What hepatic function is enhanced just before birth?
Synthesis and storage capacity for glycogen greatly increased.
116
What percentage of stored glycogen is released within the first 48 hours of life?
98%
117
When are glycogen levels restored to adult levels?
By the third week of life.
118
What percentage of adult albumin levels is present at birth?
75-80%
119
How does the newborn's ability to bind drug to plasma proteins affect drug levels?
Results in a greater level of free drug due to lower binding ability.
120
When may hyperbilirubinemia develop in term infants?
Within the first day of life.
121
What are common bilirubin levels in term infants?
6-8 mg/100mL
122
Why do neonates have problems with thermoregulation?
* Large surface area
* Poor insulation
* Small mass
* Inability to shiver
123
What is the neonate's primary defense against hypothermia?
Non-shivering thermogenesis.
124
How does hypothermia trigger heat generation in neonates?
* Stimulates norepinephrine release
* Which acts on brown fat
* To uncouple oxidative phosphorylation
125
What effect do anesthetic agents have on thermoregulation in neonates?
Inhibit thermoregulatory response.
126
How much can core temperature decrease in neonates?
1℃ to 3℃.
127
What characteristic of neonate's skin contributes to heat loss?
* Thinner skin
* Less subcutaneous tissue
* Increase evaporative heat loss.
128
What is the cardiac output in newborns and its impact?
* 200 mL/kg/min
* Faster drug delivery/removal.
129
Why do neonates need higher doses of water-soluble drugs?
Higher body water percentage.
130
How does protein binding in neonates affect drug levels?
* Lower albumin/alpha-1 acid glycoprotein
* Increased free drug levels
* Toxicity risk.
131
How does neonate's body composition affect drug duration?
* More water
* Less fat/muscle
* Longer drug action
132
What enzyme's reduction affects neonates' drug metabolism?
* Glucuronyl transferase
* Impacts bilirubin and acetaminophen metabolism.
133
When is normal GFR achieved in neonates?
8 - 24 months of age.
134
When is normal tubular function achieved in neonates?
2 years of age.
135
How does the immature BBB affect drug passage in neonates?
* Allows more drugs to enter the brain
* Increasing sensitivity to sedative-hypnotics
136
How does MAC vary in neonates and infants?
* Neonate: Lower than infant.
* Premature: Lower than neonate.
* 1-6 months: Higher than adult.
* **2-3 months: Peaks at highest level.**
137
How does the MAC requirement for sevoflurane vary from 0 days to 12 years?
* 0-6 months: Higher (3.2%).
* 6 months-12 years: Lower than 0-6 months but higher than adult (2.5%).
138
What is the required dose of succinylcholine in neonates and why?
* 2 mg/kg
* Due to increased ECF
* Normal sensitivity
139
How does increased ECF affect dosage of nondepolarizers in neonates?
* Dose remains the same as adults
* Duration may be prolonged due to immature metabolism
140
What does the FDA black box warning for succinylcholine in children under 8 highlight?
* Risk of hyperkalemia from undiagnosed muscular dystrophy
* IV calcium is priority for hyperkalemia following cardiac arrest.
141
Which neuromuscular blockers can be administered intramuscularly?
* Succinylcholine
* Rocuronium
142
What objective data suggests recovery from neuromuscular blockade?
* TOF ratio > 90%
* MIF less than -25 cm H2O.
143
What are subjective signs of adequate recovery from neuromuscular blockade?
* Grimacing
* Elbow and hip flexion
* Bringing knees to the chest
144
Which two body systems are of primary interest in a preanesthetic system review?
Respiratory and cardiovascular systems.
145
Besides respiratory and cardiovascular, what other issues are crucial for anesthesia planning?
Metabolic and structural problems.
146
What should an anesthetist assess for during a physical assessment?
Presence of congenital anomalies.
147
CV, Respiratory, metabolic and structural problems most often occur?
* SGA (Small for Gestational Age)
* LGA (Large for Gestational Age) neonates.
148
What is caudal anesthesia and when is it used?
* Most used regional anesthetic in pediatric anesthesia
* For procedures involving sacral, lumbar, or lower thoracic dermatomes
149
How is the patient positioned for caudal anesthesia?
* Lateral position with knees flexed
* Landmarks are the tip of the coccyx and sacral cornu.
150
How does the volume of local anesthetic affect caudal anesthesia?
* 1.2 to 1.5 mL/kg reaches T4-T6 dermatomes
* 1 mL/kg is used for lower procedures.
151
What guides the choice and dose of local anesthetic in caudal anesthesia?
* Practitioner’s preference
* Concentration adjusted to max 2.5 mg/kg.
