Peds anesthesia Flashcards
What is considered pre-term?
Prior to 37 weeks gestational age
What is considered the neonate?
1-28 days
What is an infant?
28 days to 1 year
What is a child considered?
greater than 1 year
The most significant transition occurs within:
24-72 hours after birth
What are some of the adaptive changes that occur?
-Establish FRC
-Convert circulation
-Recover from birth asphyxia
-Maintain core temp
During fetal respiration, where does gas exchange occur?
Placenta
O2 transport is accomplished by fetal Hgb which totals:
70-90%
Fetal Hgb shifts the oxyhemoglobin dissociation curve to the:
LEFT
(increased o2 loading in the lungs/placenta, decreased O2 unloading at the tissues)
Hemoglobin in the full term neonate is:
18-20g/dL
What fetal lung changes occur at 4 weeks?
Primitive lung buds develop from the foregut
What fetal lung changes occur at 16 weeks?
Branching of the bronchial tree complete to 28 divisions, no further formation of cartilaginous airways
What fetal lung changes occur at 24 weeks?
primitive alveoli (saccules) and type 2 cells present: SURFACTANT DETECTABLE survival possible with artificial ventilation
What fetal lung changes occur at 28-30 weeks?
capillary network surrounds saccules; unsupported survival possible
What fetal lung changes occur at 36-40 weeks?
True alveoli present- roughly 20 million at birth
What lung changes occur from birth to 3 months?
PaO2 rises as R to L mechanical shunts close
What lung changes occur until 6 years?
Rapid increase in alveoli- 350 million at age 6
How fast can the fetus “guppy breath in utero” at 30 weeks?
30% of the time- breathing at a rate of 60 breaths per min
Does the fetus respond to chemical stimuli?
yes
Normal blood gas value for newborn at term:
pH: 7.2
PO2: 50
PCO2: 48
Normal blood gas value for fetus at term at the end of labor:
pH: 7.25
Po2: 10-20
PCO2: 55
What are the changes with the onset of ventilation?
PVR decreases
Pulmonary blood flow increases
increase in PO2
decrease in Co2
When does rhythmic breathing occur?
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
What changes do the alveoli undergo?
alveoli go from fluid-filled to air-filled
How are large surface tension forces overcome?
By the small radius of the curvature of the diaphragm
infants must generate a high negative pressure: -70cm H2O, to inflate the lungs
What is the infants FRC?
approx 25-30mL/kg
Established to act as a buffer against cyclical alterations in the PO2 and PCO2 btwn breaths
What are the neonate and infant lungs prone to?
Collapse:
weak elastic recoil, weak intercostal muscles, intra-thoracic airways collapse during exhalation
What encroaches upon FRC?
High closing volumes
- small airway closure begins at volumes at or above FRC leading to lung collapse and V/Q mismatch
Why don’t infants have lung collapse all the time?
Infants terminate the expiratory phase of breathing before reaching their true FRC which results in intrinsic PEEP and a higher FRC.
What can help maintain FRC/lung inflation in the neonate during anesthesia?
PEEP of 5cm H2O
When does the respiratory system become normal?
3-4 weeks of age (but likely remains immature for some time especially in pre-term babies)
Why can neonates respond to hypercarbia?
Chemoreceptor control is present at birth
How do newborns respond to hypercarbia?
increase ventilation
But the slope of the response curve is decreased
How does hypoxia affect a neonates response to CO2?
Depresses the response to CO2
Response to hypoxia is_______.
Biphasic
Initial hyperpnea–> depression of respiration in about 2 mins
Why is the initial hyperpneic response abolished?
its abolished by HYPOTHERMIA and LOW LEVELS OF ANESTHETIC GAS
What is the most common response to hypoxia in the newborn?
APNEA
especially in pre-term infants
By 3 weeks of age, hypoxia produces:
Sustained HYPERVENTILATION
Respiratory pauses exceeding _____ or those accompanied by bradycardia or cyanosis = apnea
20 seconds
Hypoxia causes profound_____ in babies
BRADYCARDIA
Increased work of breathing =
FATIGUE
very compliant upper airway structures and ribcage which tend to collapse during inspiration
Inefficient diaphragmatic contraction
Only 25% of muscle fibers in the diaphragm are ______ fatigue-resistant work horse fibers vs. adults 55%
Type 1
What are the factors that contribute to apnea in infancy?
-Increase O2 consumption 6mL/kg
-Decreased FRC (non-functional residual capacity)
-Increased closing volume
Once hypoxia ensues, these factors will result in abnormal breathing patterns and apnea much more quickly than in the older child or adult
Where does gas exchange occur in the fetus?
Placenta
in the fetus, how much of the cardiac output do the lungs require?
5-10%
Why do fetal intracardiac and extracardiac shunts exist?
To minimize blood flow to the lungs while maximizing flow/O2 delivery to organ systems
What are the fetal shunts?
-Ductus Venosus
-Foramen Ovale
-Ductus Arteriosus
The fetal circulation is _____
PARALLEL
Deoxygenated blood travels the ______ _____ to the ____ _____ to the ______ (very low resistance to flow)
deoxygenated blood travels the descending aorta—> umbilical arteries –> placenta
Oxygenated blood returns via the _____ ______ (PO2 35 mmHg)
Umbilical vein
The _____ _____ diverts approx 50% of blood away from the liver into the IVC then to the RA
Ductus venosus
What connects the right and left atrium?
Foramen ovale
Preferential streaming causes O2 rich blood to be directed across the foramen ovale which connects the right and left atrium
O2 right blood fed to the _____ and ejected into the _____ thereby feeding the coronary and cerebral circulations
O2 rich blood fed to the LV and ejected into the aorta, thereby feeding the coronary and cerebral circulations
SVC and hepatic venous flow is delivered to the:
RV
In the fetal circulation PVR is:
HIGH
In fetal circulation, RV output is delivered across the _____ ____ which connects the PA to the descending aorta
RV output is delivered across the ductus arteriosus which connects the PA to the descending aorta
Blood entering the descending aorta returns to the _____ and feeds the lower body (PO2 22mmHg)
Blood entering the descending the aorta returns to the placenta and feeds the lower body (PO2 22mmHg)
What causes the reversal of shunts?
Umbilical cord cut:
increased SVR
onset of breathing (decreased PVR)
fetal circulation changes from parallel to _____ in transitional circulation
Fetal circulation changes from parallel to SERIES in transitional circulation
Initiation of ventilation increases arterial and alveolar PO2 which dilates pulmonary vasculature which has what effect?
PVR decreases
Pulmonary blood flow increases (450%)
____ pressure increases, ______ pressure decreases
LA pressure increases, RA pressure decreases
What percent of adults have a patent foramen ovale?
25-30%
Why does the ductus arteriosus constrict within several minutes?
D/t increases PO2, and decreased circulation prostaglandins (PGI2, PGE1)
When does the physiologic closure of the ductus arteriosus occur?
10-15hrs
When does anatomic closure of the ductus arteriosus closer?
2-3 weeks
Why does the ductus venosus close?
Becomes fibrous over time
In utero PVR is _____, SVR is _____
PVR is HIGH, SVR is LOW
Once born PVR is _____ and SVR is _____
PVR is LOW, SVR is HIGH, shunts functionally close
What is persistent pulmonary hypertension of the newborn (PPHN)?
Persistence of fetal shunting beyond the normal transition period in the absence of a structural heart defect
Bc the shunts are not anatomically closed immediately after birth, certain clinical conditions may contribute to either the persistence of or a return to fetal circulation
What are the consequences of hypoxia and acidosis?
Increased PVR
Pulm HTN
Decreased pulmonary blood flow
RAP> LAP
increased ductal flow
All can open the foramen ovale
What are the signs and symptoms of persistent pulmonary hypertension? (PPHN)
-Marked cyanosis
-Tachypnea
-Acidosis
-Right to left shunt across the foramen ovale, and ductus arteriosus= marked cyanosis (right to left= cyanotic shunt)
Before anatomic closure of the fetal shunts, transient right to left shunting may occur in neonates during:
Coughing, bucking, or straining during anesthetic induction or emergence
What is the treatment for PPHN?
-Hyperventilation (to maintain alkalosis)
-Pulmonary vasodilators -prostaglandins
-Minimal handling
-Avoidance of stress
Adequate ventilation and oxygenation is KEY
What is the major function of the fetus’s renal system?
passive production of urine which contributes to the formation of amniotic fluid
Why is amniotic fluid important?
Important for normal development of the fetal lung and acts as a shock absorber for the fetus
What are the characteristics of the fetal kidney?
Low renal blood flow
Low glomerular filtration rate (GFR)
What are the reasons for the fetus’s low renal blood flow and GFR?
-Structurally immature small size and number of glomeruli
-Low systemic arterial pressure
-High renal vascular resistance
-Low permeability of glomerular capillaries
What are the transitional changes of the renal system in the newborn?
-Systemic arterial pressure increases
-renal vascular resistance decreases
-increase in size and function occur through maturity
By _____ weeks, all nephrons are developed, so a premature baby has incomplete renal development
34 weeks
In the first several days of life in the full-term infant there is a diminished ability to _____ ______ resulting from low GFR at birth
concentrate urine
Urine osmolarity:
700-800 mOsm/L
Creatinine:
0.8-1.2 mg/dL
The neonate excretes ____ even in the presence of a severe Na deficit
Na
the neonate is therefore considered an “obligate sodium loser”
Urine Na in the neonate:
20-25 mEq/L
What fluid should be used for all neonates and premies?
D5.2% NS
What happens in the first 3-4 days in terms of the renal system?
Increased renal blood flow
decreased renal vascular resistance
neonate will have an increased ability to concentrate urine w time.
What is the lowest acceptable blood loss for a baby?
35% bc of high o2 demand w limited ability to increase CO
Increased blood volume per unit weight
Increased CO per unit weight
blood volume of a term baby:
90mL/kg
blood volume in pre-term baby:
100mL/kg
what maintains a stable core temp during changes in ambient temperature
Homoeothermic organisms
the neonate’s limited thermal range is a function of their:
-small size
-increases surface to volume ratio
-increased thermal conductance
What are the 2 stages of heat loss?
Transfer of heat from body core to skin surface (internal temperature gradient)
Dissipation of heat from the skin surface to the environment ) external heat gradient)
Factors that control conductive loss in infants:
cutaneous blood flow
Insulation- the amount of subcutaneous tissue
prevention: warm blankets, heating mattress, bair hugger
Heat production is achieved by:
-voluntary muscle activity
-involuntary muscle activity
- nonshivering thermogenesis- major component in neonate
What is brown fat metabolism?
-Develops in the fetus btwn 26-30 wks gestation
-Comprises 2-6% of the neonates total body wt.
-Located in the mediastinum btwn the scapula, around adrenals, in axilla
-Abundant vascular supply and rich innervation of the SNS
What is non-shivering thermogenesis?
-occurs w cold stress
-mediated by the SNS
-heat produced is a product of fatty acid metabolism
What are the consequences of cold stress?
- increase o2 consumption
-hypoxia
-acidosis
-increase glucose utilization
-release of lactic acid
-hypoglycemia
-decreased surfactant production
-collapse of alveoli
-reopening of fetal circulation (foramen ovale and ductus arteriosus)
Resuscitation starts:
in utero
What is the fetal baseline heart rate?
120-160bpm
What would a decrease in the fetal baseline heart rate indicate?
may indicate asphyxia
What would cause short-term variability? 3-6bpm
CNS depressants reduce short term variability
What is long-term variability?
characterized by periodic accelerations correlating w fetal movements normally 15-40 accelerations per hour. Decreases are seen w fetal sleep
What would the absence of short and long term variability indicate?
FETAL DISTRESS
What would the absence of short and long term variability indicate?
FETAL DISTRESS
What causes early decelerations?
Vagal response to head compression, not associated w distress
What causes late decelerations?
Uteroplacental insufficiency. Decreased O2 supply, combined w lack of short-term variability, is ominous for fetal distress.
What causes variable decelerations?
Related to cord compression, associated w fetal asphyxia when they are greater than 70 bpm, longer than 60 seconds, or occur in a pattern persisting for more than 30 mins
What causes variable decelerations?
Related to cord compression, associated w fetal asphyxia when they are greater than 70 bpm, longer than 60 seconds, or occur in a pattern persisting for more than 30 mins
How an you obtain a fetal blood sample?
Can be obtained via scalp puncture after membranes ruptured
Normal fetal pH?
7.25-7.35 (7.33 mean)
PO2: 20-30
PCO2: 40-50
What is a borderline fetal pH?
7.20-7.25
What pH may be associated w a depressed neonate?
<7.20 needs O2
What are the categories of the APGAR score?
-Activity
-Pulse
-Grimace
-Appearance
-Respiration
The resuscitation of the neonate is primarily the responsibility of who?
the neonatal care team
Anesthesia’s primary responsibility is:
the mother
Anesthesia’s primary responsibility is:
the mother
When resuscitating the neonate what should the RR be?
30-60 breaths per minute
What rate should you bag mask a neonate?
40-60 breaths per min w 100% o2
Initial breaths may require how much pressure?
40cm H2O
After the initial breaths, what pressure should be maintained when bagging a neonate?
below 30 cm H20
When resuscitating a neonate what should the HR be kept at?
> 100 bmp
when should chest compressions be started on a neonate?
if HR <60 or 60-80 and not rising
Compressions at 120 bpm and intubate.
How do you know you have the correct ETT size?
indicted by small leak at 20 cm H2O
It is critical to keep infant ____ during resuscitation
WARM
It is critical to keep infant ____ during resuscitation
WARM
How often is the APGAR score taken?
1 min, and 5 mins
when would you retake an APGAR score after the initial 2?
If 5 min score is less than 7- repeat every 5 mins until 20 mins have passed or 2 successive scores are greater or equal to 7
When is survival of the neonate unlikely?
When APGAR score is 0 at 10 mins
ETT size and depth at < 28 wks?
2.5 uncuffed
6-7 cm at lips
ETT size and depth at 28-34 weeks?
3.0 uncuffed
7-8 depth at lips
ETT size and depth at 34-38 weeks
3.5 uncuffed
8-9 cm from lips
What ETT size and depth at >38 weeks
3.5-4 (3.0) uncuffed
9-10 cm at lips
If the neonate has a low BP what should be ruled out?
hypoglycemia
hypermagnesmia
hypocalcemia
If the neonate has a low BP what should be ruled out?
hypoglycemia
hypermagnesmia
hypocalcemia
normal BP for 1-2kg infant:
50/25
normal BP for a >3kg infant
70/40
If the neonate has a low BP, what can be given?
10mL/kg LR or NS
When are meds indicated during neonatal resuscitation?
if HR remains <60 bpm w adequate ventilation w 100% o2 and chest compressions for 30 seconds
where can drugs be administered in the neonate?
Peripheral vein, umbilical vein, ETT
When and how much Epi would be administered?
Epi: 0.01-0.03 mg/kg for bradycardia or asystole despite quality compressions
May administer 1mL of saline via ETT
How much and when would naloxone be administered to the neonate?
0.1mg/kg IV or ETT
0.2mg/kg IM
to antagonize respiratory effects of narcotics given during labor
How much and when would you administer sodium bicarb?
1 mEq/kg IV slowly over 2+ mins for acidosis
Increased doses are typically recommended for ETT in _____ resuscitation but NOT recommended for ______ resuscitation
pediatric, neonatal
What percentage of a term newborn’s total body weight consists of water?
A. 45%
B. 60%
C. 75%
D. 90%
C. 75%
What is the maximum allowable blood loss (MABL) for a 10-kg, 11-month-old infant whose starting hematocrit (Hct) is 36 and the minimal acceptable Hct is 25?
A. 110 mL
B. 245 mL
C. 350 mL
D. Cannot be calculated without additional
information
B. 245 mL
Reasons for selecting a cuffed endotracheal tube over an uncuffed endotracheal tube include all of the following EXCEPT
A. Fewer intubations and endotracheal tubes
are needed
B. Less chance for airway fires
C. Spontaneous breathing is easier
D. Aspiration of gastric contents is less likely
C. Spontaneous breathing is easier
A healthy 3-kg, 1-month-old neonate is anesthetized for an inguinal hernia repair. An inhalation induction with sevoflurane is carried out and the patient is intubated. Before the surgical incision, the systolic blood pressure is noted to be 65 mm Hg and the heart rate is 130 beats/min. The most appropriate intervention for this patient’s blood pressure would be
A. Administration of ephedrine
B. Administration of phenylephrine C. 50-mL fluid bolus
D. None of the above
D. None of the above
At what maximum inspiratory pressure should an endotracheal tube leak in a child?
A. 5 to 15 cm H2O
B. 15 to 25 cm H2O
C. 25 to 35 cm H2O
D. None of the above
B. 15 to 25 cm H2O
Which of the following is the most suitable replacement fluid for a 3-year-old, 14-kg child undergoing repair of clubfeet?
A. D5W
B. D5 1⁄2NS
C. Normal saline
D. Lactated Ringer solution
D. Lactated Ringer solution
The most common cause of neonatal bradycardia (heart rate <100 beats/min) in the delivery room is
A. Congenital heart disease
B. Maternal drug intoxication (narcotics, alcohol,
magnesium, barbiturates, digitoxin)
C. Postpartum cold stress
D. Hypoxemia
D. Hypoxemia
The spinal cord of newborns extends to the
A. L1 vertebra
B. L2-L3 vertebrae
C. L4-L5 vertebrae
D. S1 vertebra
B. L2-L3 vertebrae
A 4-kg, 3-hour-old newborn with macrosomia and large fontanelles is scheduled for surgical repair of an omphalocele. Physical examination reveals macroglossia but no other anomalies. Which of the following is likely to occur in this patient?
A. Hyperkalemia
B. Metabolic acidosis
C. Hypoxemia
D. Hypoglycemia
D. Hypoglycemia
The predicted blood volume in a 4-kg neonate is
A. 240 mL
B. 280 mL
C. 340 mL
D. 400 mL
C. 340 mL
The pulmonary vascular resistance in newborns decreases to that of adults by age
A. 1 to 2 days
B. 1 to 2 weeks
C. 1 to 2 months
D. 1 year
C. 1 to 2 months
A 12-hour-old, 1800-g neonate, 30 weeks’ postges- tational age, is noted in the ICU to begin making twitching movements. Blood pressure is 45 mm Hg systolic, blood glucose is 50 mg/dL, and urine output is 5 mL/hr. The O2 saturation on pulse oximeter is 88%. The MOST appropriate course of action to take at this point would be
A. Administer calcium gluconate (2 mL of 10% solution)
B. Glucose 10 mg IV over 5 minutes (2 mL of D5W)
C. Hyperventilate with 100% O2
D. Administer a 20-mL bolus of 5% albumin
A. Administer calcium gluconate (2 mL of 10% solution)
Advantages of catheterization of the umbilical artery versus the umbilical vein in a newborn include all of the following EXCEPT
A. It allows assessment of oxygenation
B. Hepatic damage from hypertonic infusion is avoided
C. It permits assessment of systemic blood pressure
D. It is easier to cannulate
D. It is easier to cannulate
The TRUE statement concerning thermoregulation in neonates is which of the following?
A. A significant proportion of their heat loss can be
accounted for by their small surface area–to-weight
ratio
B. They compensate for hypothermia by shivering
C. The principal method of heat production is
metabolism of brown fat
D. Heat loss through conduction can be reduced by
humidification of inspired gases
C. The principal method of heat production is
metabolism of brown fat
Normal values for a healthy 6-month-old, 7-kg infant include
A. Hemoglobin 17 g/dL
B. Heart rate 90 beats/min
C. Respiratory rate 30 breaths/min D. Systolic blood pressure of 60
C. Respiratory rate 30 breaths/min
Which of the following respiratory indices is increased in neonates compared with adults?
A. Tidal volume (Vt) (mL/kg)
B. Alveolar ventilation (mL/kg/min)
C. Functional residual capacity (mL/kg)
D. Paco2
B. Alveolar ventilation (mL/kg/min)
Which of the following statements regarding resusci- tation of the infant by health care providers is NOT correct?
A. Mouth-to-mouth or mouth-to nose ventilation at
a rate of 12 to 20 breaths/min is performed when breathing is inadequate but an adequate pulse is present
B. Start chest compressions when the pulse is less than 60 beats/min and there are signs of poor tissue perfusion
C. Chest compression depth is 1/5 the anteroposterior diameter of the chest (about 1 cm)
D. Compression-to-ventilation ratio is 30:2 for one- person and 15:2 for two-person cardiopulmonary resuscitation (CPR)
C. Chest compression depth is 1/5 the anteroposterior diameter of the chest (about 1 cm)
All of the following are true statements concerning physiology of newborns compared with that of adults EXCEPT
A. Newborns have a greater percentage of total body
water compared with adults
B. Newborns have a higher glomerular filtration rate
(GFR) than adults
C. Newborns’ hearts are relatively noncompliant
compared with adults
D. Newborns’ diaphragms have a lower proportion of
type I muscle fibers (i.e., fatigue resistant, highly oxidative fibers)
B. Newborns have a higher glomerular filtration rate
(GFR) than adults
Which of the following statements concerning the anatomy of the infant and the adult airway is NOT true?
A. An infant’s tongue is relatively large in relation to
the oropharynx compared with an adult’s B. The larynx is in a more cephalic position in
infants than in adults
C. The vocal cords are in a more horizontal position
within the larynx in infants than in adults
D. The narrowest part of the infant and adult larynx
is at the level of the cricoid cartilage
C. The vocal cords are in a more horizontal position
within the larynx in infants than in adults
In the infant, hypothermia would LEAST likely manifest as
A. Metabolic acidosis
B. Prolonged duration of action of nondepolarizing
muscle relaxants
C. Hyperglycemia
D. Bradycardia
C. Hyperglycemia
In a newborn, access to the vena cava can be gained by passage of a catheter through the
A. Ductus arteriosus
B. Ductus venosus
C. Umbilical arteries
D. Foramen ovale
B. Ductus venosus
Preoperatively, hypotension (i.e., decompensated shock) is characterized by a systolic blood pressure
A. Less than 60 mm Hg for the term neonate
(0-28 days old)
B. Less than 70 mm Hg for infants 1 to 12 months old
C. Less than 70 mm Hg + (2 × age in years) for chil-
dren 1 to 10 years old
D. All of the above
D. All of the above
What percent of the adult’s GFR (indexed to body surface area) does a 2-year-old possess?
A. 30%
B. 50%
C. 75%
D. 100%
D. 100%
