Pediatric Anesthesia Quiz #2 Flashcards
During fetal circulation, PVR is _____ and SVR is _____.
- PVR is high (the lungs are bypassed)
* SVR is low
What is the Foramen Ovale?
– Foramen ovale (“hole” in the atrial septum = connecting RA with LA) ->because PVR is high, blood shunts from
Right to Left (bypassing the lungs)
What is the Ductus Arteriosus?
– Ductus Arteriosus (connection between PA (Pulm. Artery) and Aorta = blood flows from RA – tricuspid valve
into RV->blood bypasses the lung again to take the short‐cut to the aorta(systemic circulation).
After birth, the neonate takes its first breaths, the lungs inflate and ___ reduces while the placenta is disconnected and blood is “not drained back to
mom” – increasing ___.
- PVR
- SVR
After birth….how do these pressure changes affect fetal circulation?
> With these pressure changes blood flows easier into the lungs and becomes oxygenated.
Also, the increased pressure in the LA (compared with RA) pushes the flap of the foramen ovale shut.
The increased pressure in the aorta allows some “back flow” of blood via the ductus arteriosus back into
the pulm. artery (PA) which causes additional oxygenation of the blood.
Eventually, the pressure changes within the two circulations and the reduced levels of prostaglandins
causes the closure of the ductus arteriosus (DA) and foramen ovale (FO) within days after birth.
What causes the foramen ovale to close in the newborn?
- the closure of the foramen ovale is due to the decrease in PVR and increase in pulmonary flow that accompanies with the infants first breaths and the expansion of the alveoli.
- the decrease in PVR is accompanied by contraction of the ductus arteriosus secondary to oxygenation
- this results in an increase in pulmonary blood flow and an increase in left arterial pressure
- the increased pressure in the LA shuts the flap, located on the left side of the foramen ovale
Identify 4 factors that may cause neonate/infant to return to fetal circulation?
- hypoxemia, acidosis, pneumonia and hypothermia are 4 primary precipitating factors in persistent fetal circulation.
- the pathologic mechanism common to all 4 factors is increased PVR and right-to-left shunting
What is the significance of the Ductus Venous?
-Ductus Venosus: (connection between the
umbilical vein and IVC) ‐ most umbilical venous
blood from the placenta bypasses the liver ->
IVC ->RA
-Blood supplied to heart / upper body has higher
oxygen content (65%) vs. that supplied to
abdominal organs, lower limbs, and placenta
(55%‐60%).
What happens as the infant is transitioning to breathing air?
Decreased PVR and increased SVR (loss of the umbilical circulation) are the two crucial events involved in the immediate transition from the fetal circulation to the
normal postnatal pattern.
The increase in systemic afterload causes an immediate closure of the flap valve mechanism of the foramen ovale and reverses the direction of shunt through the ductus arteriosus.
Blood shunts through what two structures in the neonate with persistent fetal circulation?
Blood shunts through the ductus arteriosus and the former ovale.
During the early neonatal period, reversion to the fetal circulation can occur: If hypoxia occurs, PVR
increases and reopens the ___ ___ which will lead to what?
- ductus arteriosus
- decline in arterial oxygenation which results in
acidosis which further increases PVR -> hypoxemia
If SVR remains higher than PVR -> left‐to‐right shunt (pink baby– transitionally ok!) but if PVR becomes more increased due to hypoxia and acidosis, previous fetal circulation may occur via patent foramen ovale
[PFO] and/ or patent ductus arteriosus [PDA] leading to this type of shunt and to this clinical picture.
- right-to-left shunt
- cyanotic baby
In the newborn, hypoxia causes what 4 things?
- pulmonary vasoconstriction
- systemic vasodilation
- bradycardia
- decreased cardiac output
Rapid intervention is necessary to prevent
this state from proceeding to cardiac arrest.
-> Give Atropine & 100% oxygen
List two ways the physiology of the cardiovascular system of the neonate differs from that of the adult?
- cardiac output is heart-rate dependent
2. left-ventricular compliance is decreased
What PaO2 and SaO2 are appropriate during anesthesia for the premature infant?
SaO2 in the 90-95%(PaO2 = 60-80 mmHg) is believed to be reasonable for the premature infant.
What is the normal heart rate of the term infant(term neonate)?
120 - 180 bpm
What is the estimated blood volume of the preterm neonate?
90 - 100 ml/kg
What is the estimated blood volume of the full-term neonate?
80 - 90 ml/kg
What is the estimated blood volume of an infant(
70 - 80 ml/kg
What is the estimated blood volume of a school-age child(
70 ml/kg
What is the estimated blood volume of a teenager(>12yrs)/Adult?
65 - 70 ml/kg
What is the estimated blood volume of an obese child?
60 - 65 ml/kg
The hypovolemic infant is unable to maintain an ___ ___, hence, accurate early volume replacement is essential.
-adequate CO
-The infant’s systolic arterial BP is closely related to the
circulating blood volume. Blood pressure is an
excellent guide to the adequacy of blood replacement
during anesthesia.
What is a neonates Hgb and Hct?
Hct=60%
Hgb=18-19 g/dl
At birth 50 - 70% of Hgb is _____ which has a higher affinity for oxygen —> picks-up more O2 but does not deliver it to the tissues(this describes what type of shift of the oxyhemoglobin dissociation curve?
- HgbF
- Shift to the left
What are the characteristics of H&H as the infant reaches 2-3 months old, 3 months to a year old?
And how are these characteristics affected if the infant was preterm?
- 2-3 months old-> H&H declines steadily -> Hgb 9-11 g/dl and HgbF is largely replaced by HgbA
- After 3 months to 1 year, HgbA increases to 12-13 g/dl
- In the preterm infant: earlier and greater fall in Hgb(7-8 g/dl)
Despite the reduction of Hgb, the oxygen delivery to the tissues may not be compromised d/t the oxygen-hemoglobin dissociation curve shift to the right(more HgbA)
The oxyhemoglobin dissociation curve of the newborn is shifted to the left or the right?
- Left!
- Fetal Hgb does not bind with 2,3 DPG. Thus the newborn’s oxyhemoglobin dissociation curve will be shifted to the left.
- This gives the fetus the advantage of loading more oxygen at low fetal oxygen partial pressures
What happens to the oxyhemoglobin dissociation curve during the first few months of life? why?
- The oxyhemoglobin dissociation curve shifts to the right.
- As fetal Hgb is replaced by adult Hgb(at 3-4 months of age, infants have increased levels of 2,3 DPG as compared to adults), the infants P50 increases(the curve shifts to the right) to approximate that of the adult, enhancing O2 delivery.
What is the hemoglobin concentration at 2 weeks of age, 2-3 months of age, and 2 years of age?
- At 2 weeks: Hgb is 13-19 g/100 ml of blood
- At 2-3 months: Hbg is less than 10-11 g/100 ml of blood
- At 2 years: Hgb is less than 12.5 g/100 ml of blood
Describe the physiological anemia of the neonate and pediatric patient.
The Hgb concentration progressively “bottoms out” during the 9th to 12th week reaching a minimum of 10-11 g/dl, with a hematocrit of 33%.
compare the physiological anemia in the preterm neonate to the full-term neonate.
In preterm infants, the decrease in Hgb level is greater and earlier, reaching the minimum Hgb concentration of 8 g/dl by 4-8 weeks(Hgb “bottoms out” earlier and lower)>
Below what Hgb concentration is anemia sufficient to jeopardize O2 carrying capacity(and hence cause you to cancel elective surgery) in the neonate and infant older than 3 months?
Less than 13 g/dl in the newborn and less than 10 gel in the pediatric patient older than 3 months
The 3 month old infant, who is scheduled for surgery has a Hgb of 10.5 g/dl. What action should be taken?
None. This Hgb level is normal for the age. At three months of age, Hgb concentration normally decreases to this level.
What are 4 altered pharmacokinetics seen in children that is different than in adults?
- altered protein binding(babies don’t have a lot of muscle mass)
- larger volume of distribution(think “yellyfish”-lots of water)
- smaller proportion of fat and muscle stores
- immature renal and hepatic function
What is the pediatric PO dose of midazolam?
0.5 - 0.7 mg/kg(max 20 mg)
What is the pediatric dose of IV cefazolin?
25 mg/kg
What is the pediatric dose of IV succinylcholine?
1.5 - 2 mg/kg
What is the pediatric dose of IV atropine?
- 01 - 0.02 mg/kg(no less than 0.1 mg)
* 10-20 mcg/kg IV or 20-40 mcg/kg IM*
What is the pediatric dose of IV propofol?
2-4 mg/kg
What is the pediatric dose of IV vecuronium?
0.1 mg/kg
What is the pediatric dose of IV fentanyl?
1-2 mg/kg
What is the pediatric dose of IV hydromorphone?
10-20 mcg/kg
What is the pediatric dose of IV neostigmine?
0.07 mg/kg(max 5 mg)
What is the pediatric dose of IV glycopyrrolate?
- 01 mg/kg(10 mcg/kg)
* Give at least 100 mcg*
What is the pediatric dose of IV ondansetron?
0.1 mg/kg
What weight would a size 1 LMA be appropriate for?
What weight would a size 1.5 LMA be appropriate for?
5- 10 kg
What weight would a size 2 LMA be appropriate for?
10 - 20 kg
What weight would a size 2.5 LMA be appropriate for?
20 - 30 kg
What weight would a size 3 LMA be appropriate for?
30 - 50 kg
What weight would a size 4 LMA be appropriate for?
50 - 70 kg
What is the formula for correct ETT in the pediatric population?
> 2 years of age:
UNCUFFED: age + 16/4
CUFFED: [age + 16/4]—>go down a 1/2 size
Where should the ETT be taped at in a term infant?
10 cm
Where should the ETT be taped at in a 1 year old?
11 cm
Where should the ETT be taped at in a 2 year old?
12 cm
Where should the ETT be taped at in a 6 year old?
14-15 cm
Where should the ETT be taped at in a 10 year old?
16-17 cm
Where should the ETT be taped at in a 16 year old?
18-19 cm
Where should the ETT be taped at in a 20 year old?
20-21 cm
What is the does for IV lidocaine?
1mg/kg
What is the dose for IV versed?
0.05 mg/kg
What is the tidal volume of a neonate in ml/kg?
-a neonate should have a ventilator setting for tidal volume of 7 ml/kg(6-8 mg/kg is the normal range)
What is the minute volume per kg for a neonate?
- Vt in a neonate is 7 ml/kg and RR is 30-50 bpm.
- minute ventilation = Vt x RR
- an estimate of Ve in the neonate is: ~250 ml/kg
What are the recommendations for as related to preterm infants and discharge from the PACU?
- it is recommended that former preterm infants who are 55 to 60 weeks PCA and who are not anemic and not experiencing apnea be observed for an extended period of time and if stable later discharged.
- However, infants younger than 55 weeks PCA those who are anemic(hct
The difference in pharmacokinetics between children and adults may result in?
These factors and individual differences in drug metabolic enzymes may reduce a drug’s
metabolism and/or delay elimination
When do liver enzymes become completely functional in the neonate?
The cytochrome P450 system is fully functional at one month of age
What is the most common cause for liver transplantation in children?
cholestatic liver disease secondary to biliary atresia
What causes physiologic jaundice in the newborn?
Physiologic Jaundice is due to the breakdown of RBCs (which release bilirubin into the blood) and to the immaturity of the newborn’s liver (which cannot effectively metabolize the bilirubin and prepare it for
excretion into the urine).
Normal physiologic jaundice of the newborn typically appears……
between the 2nd and the 5th days of life and clears with time.
What is Kernicterus and what is the treatment?
(Bilirubin Encephalopathy):
A grave form of jaundice of the newborn characterized by very high levels of unconjugated bilirubin in the blood and by yellow staining and degenerative lesions in the cerebral gray matter.
Tx: phototherapy and exchange transfusions.
What drugs may cause kernicterus in the neonate?
- Furosemide
- Sufonamides
- Diazepam(the preservative benzyl alcohol is the actual culprit
What causes frequent “spitting up” in infants?
With the immaturity of the pharyngo‐esophageal
sphincter, frequent regurgitation or “spitting”
of gastric contents is observed even in healthy
infants.
Gastroesophageal reflux is one of a number of
conditions associated with apnea and bradycardia in
preterm infants.
Uncontrolled maternal hyperglycemia results in hypertrophy and hyperplasia of the fetal islets of Langerhans which leads to…..
This leads to increased levels of insulin in the fetus, affecting lipid metabolism and giving rise to a
large, overweight infants.(so large amounts of maternal glucose makes the baby to make more insulin)
The placenta is impermeable to both insulin and glucagon. The islets of Langerhans in the
fetal pancreas, however, secrete insulin from the 11th week of fetal life.
Uncontrolled maternal hyperglycemia result in
hypertrophy and hyperplasia of the fetal islets of Langerhans.
Hyperinsulemia of the fetus persists after birth and may lead to…….
Hyperinsulemia of the fetus persists after birth and may lead to rapid development of serious hypoglycemia (
Why are insensible fluids losses relatively high during infancy?
- high level of alveolar ventilation
- thin skin of LBW infants
Why does dehydration develop rapidly in infants when intake is restricted or losses occur?
- because of infants proportionally higher water turnover
- the limited ability to concentrate urine and conserve water
What are the prep NPO requirements for children as related to clears, breast milk, infant formula and solids?
Clear liquids: 2 hours(chewing gum 2 hours)
Breast milk: 4 hours(easier to break down than infant formula
Infant formula: 6 hours(light meal, dry crackers/toast/no fat/no meat/no protein)
Solids(fatty) 8 hours(peanut butter and cracker for example)
What is the Fluid deficit and replacement rule for the pediatric patient?
4 ml/kg for the first 10 kg
2 ml/kg for the second 10 kg
1 ml/kg for the remaining kg of weight
Pediatric fluid replacement for blood loss is best determined by which method of monitoring?
Hematocrit
At what age is the basal metabolic rate normally the highest?
BMR peaks somewhere between 6-12 months of age.
100 cal/kg/day(1 year old)
35 cal/kg/day(adults)
Why are infants markedly predisposed to hypothermia?
Preterm and full‐term neonates and small infants
have both a large skin‐surface area compared to
body mass ratio and increase thermal
conductance (thin layer of subcutaneous fat).
loses heat easily>
Furthermore, evaporative heat loss is greater in
infants as a result of reduced keratin content in
the infant’s skin.
The combination of increased heat loss and
diminished efficacy of the thermoregulatory
response with reduced ability to generate heat
markedly predisposes the infants to
hypothermia.
Blood flow to our body’s surface encourages heat
loss by four primary processes:
Radiation:
Convection
Conduction
Evaporation
Describe heat loss by radiation
Radiation is the most significant mechanism of
heat loss by our bodies, esp. by patients under
anesthesia.
Radiation of the infrared electromagnetic
wavelength transfers heat energy from our warm
bodies to the less warm OR environment (walls,
ceiling, equipment, etc.)
Our heads lose the greatest amount of heat
due to the high percentage of blood flow.
Describe heat loss by convection
Convection is the process of creating air currents by
heat.
Our bodies transfer kinetic energy to air molecules on
the surface of our skin.
The heated air molecules then move about with
greater kinetic energy, rise, and are replaced by colder
(less kinetic energy) air molecules.
Our bodies then transfer more kinetic energy to these
molecules, they rise, and again are replaced by cooler
air molecules.
When thinking of convection, it helps to think in terms
of currents (wind chill factor).
Describe heat loss by conduction
Conduction is the transfer of heat by physically
touching a less warm object. Where two objects are
in direct contact, heat exchange occurs from high
concentration to lower concentration (entrophy).
An example would be holding ice cubes in your hand,
the sensation of cold is the direct loss of heat from
your hand to the ice cubes.
Cold is not transferred to your hand; heat is
transferred to the ice cubes).
Describe heat loss by evaporation
The process of breathing also causes heat
loss through exhaled water vapor. This is
usually not a high heat loss method in adult
patients, but may become significant in
pediatric patients when using high carrier
gas flow rates.
Lower carrier gas flows, when appropriate,
and use of in‐line humidifying apparatus
decrease the evaporation of pulmonary
water content and limit heat loss by this
mode.
Approximately what percent of total heat loss from the body normally occurs by radiation and convection combined?
70%(40% by radiation/30% by convection)
Through which route does a burn patient lose the highest percentage of body heat?
Evaporation
Heat is lost from the body in what order from most to least?
- Radiation
- Convection
- Evaporation
- Conduction
When does the posterior fontanelle close?
at about 4 months of age
When does the anterior fontanelle close?
at about 9-18 months of age
At what gestational age does the risk of ROP become negligible?
after 44 weeks PCA because retinal vasculogenesis is complete between 42-44 weeks PCA
Neontal ROP is a result of oxygen toxicity > what %?
40%
