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64 Cards in this Set
- Front
- Back
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Define neonate |
< 28 days |
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Define Infant |
1 month - 1 year |
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Define Child |
> 1 year |
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A neonate weighs ________ as much as an adult |
1/21 |
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Neonatal BSA is ______ as much as an adult |
1/9 |
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What are the consequences of large relative body surface area of a neonate |
Higher heat loss Higher insensible fluid loss |
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__________ of a neonate's body surface area is its head |
20%
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A neonate is ____ as tall as an adulg |
1/3 |
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An adult head is ______ of its TBSA |
1/8 |
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Describe what parallel circulation in the fetusmeans |
Systemic circulation exits both the left and right sides of the heart |
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In utero pulmonary vascular resistance is ______ Systemic vascular resistance is ________ why? |
Very high PVR (fluid filled/atelectatic alveoli, HPV)
Very low SVR (low resistance placenta) |
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There is ________ to ________ shunting across the ductus arteriosis and formen ovale. |
Right to left |
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Deoxygenated blood is pumped down the fetal descending aorta in to the two ________ into the placenta |
umbilical arteries |
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What are the two functions of the placenta |
Respiratory center
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How much aortic blood enters the placenta from the descending aorta? |
50% |
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What percent of blood returning from the placenta bypasses the liver? How is this accomplished? |
50 percent bypasses liver via ductus venosus |
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A large portion of fetal blood entering the RA from the IVC is shunted directly to the LA via the ________________ |
foramen ovale |
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A large portion of deoxygenated blood enters the RA from the SVC, travels to the RV, enters the pulmonary artery and flows directly into the aorta via ____________ Why does this occur? |
ductus arteriosis due to high pulmonary vascular resistance |
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What direction does blood travel through a PFO? |
Normally does not (left sided heart pressures > right sided heart pressures) |
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When will right to left shunting occur through a PFO? What conditions predispose a neonate to this? |
If RAP > LAP Occurs under conditions of hypothermia, hypoxia, hypercarbia, and acidosis. (these increase pulmonary vascular resistance) |
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Where is the highest oxygen saturation observed in the fetal circulation? |
Umilical vein (70-80%) |
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How much of the right ventricular output flows into the pulmonary vascular blood? |
5-10% |
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The fetal right ventricle receives and pumps what portion of fetal blood? What is the muscle mass of the fetal right ventricle compared to the left? |
Fetal RV pumps 2/3 of fetal blood Has 25% more muscle mass |
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What circulatory changes occur at birth in the pulmonary circulation? |
Spontaneous respiration = removal of fluid from alveoli and increase in alveolar oxygen tension Increased alveolar O2 tension causes vasodilation of the pulmoary vascular bed and decrease in pulmonary vascular resistance |
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How does clamping of the umbilical cord affect circulation? |
Significant increase in systemic vascular resistance. Decrease in IVC blood flow and RA pressure |
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Overall affect of circulatory changes at birth: |
Dec. PVR + Inc. SVR = marked increase in pulmonary blood flow and pressure in left side of heart |
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How does the ductus venosus close? |
Ligation of the umbilical vein changes portal pressures, triggering closure of the ductus venosus. |
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When does the ductus venosus close? |
1-3 hours after birth (functional closure) 2 weeks of life (anatomic closure) |
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How does the foramen ovale close? |
LAP exceeds RAP (due to pulmonary and systemic changes) |
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When does foramen ovale close? |
Functional closure soon after birth Anatomic closure by 2-3 months of age |
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What can cause the Foramen Ovale to re-open |
hypoxia, hypercarbia, acidosis, hypothermia straining/coughing/vagal manuvers/bucking on ventilator |
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What are the consequences of right to left shunting? |
Hypoxia
Embolic events (stroke, TIA, MI) Migraines |
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What causes the ductus arteriosus to close? |
Increased arterial oxygen tension and a reduction in circulating prostaglandins |
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What can cause the ductus arterosus to re-open |
Hypoxia, hypercarbia, hypothermia, acidosis |
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When does anatomic closure of the ductus arterosus occur? |
Requires 1-3 months Thrombosis and fibrosis |
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What is PPHN |
persistent pulmonary hypertension of the newborn = life threatening cardiopulmonary disorder of newborn that occurs when pulmonary vascular resistance remains elevated or increases early in the neonatal period. |
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What causes PPHN? |
Continuation or return to right to left shunting (through FO and DA) |
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What are the effects of PPHN |
Significant proportion of venous blood diverted away from the lungs and enters systemic circulation -systemic hypoxemia -worsening pulm HTN (shunting etc...) |
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Who is at risk for PPHN? |
Premature infants < 37 weeks Critically ill neonates |
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Triggers/causes of PPHN |
Pulmonary vasoconstriction due to acute perinatal events -alveolar hypoxia (meconium aspiration, hyaline membrane disease RDS) -hypoventilation (asphyxia, inadequate mechanical ventilation) -hypothermia -acidosis (infection/sepsis) |
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Additional causes of PPHN |
Idiopathic pulmonary HTN w/ normal CXR -abnormal remodeling of pulmonary vascular bed -maternal administration of NSAIDS/SSRIs during second half of pregnancy Hypoplasia of pulmonary vascular bed -congenital diaphragmatic hernia -Oligohydraminos (deficiency of amniotic fluid) |
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Treatment of PPHN |
Find and treat cause
-supplemental FiO2, -hyperventilation -maintain normal BP -Nitric oxide, PGI2 -HFJV (oscilator), ECMO |
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Incidence of patent foramen ovale |
50% of children less than 5 25% of adults |
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Can right to left shunting occur in PFO? |
Yes of RAP > LAP |
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Consequences of right to left shunting in PFO |
hypoxemia emboli (air, thrombi) - entering systemic circulation |
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Can left to right shunting occur in PFO |
Very rare |
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Treatment for PFO |
If symptomatic -reduce RA pressures (inotropes, NO) -prevent thrombus formation (anticoagulation) -PFO closure (surgical or percutaneous) |
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Compare rate of inhalation induction in individuals with R-L shunting VERSUS L-R shunting |
Slower with R-L shunting (less pulmonary bloodflow) Faster with L-R shunting |
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Compare rate of IV induction in individuals with R-L shunting vs. L-R shunting |
Faster with R-L shunting (more systemic blood flow/less pulmonary blood flow) Slower with L-R shunting |
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What is the incidence of ASD? |
Most common heart defect 1:1500 live births |
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Normal shunt flow in ASD |
Left to right (unless RAP > LAP - i.e. pulm htn) |
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Intervention for ASD |
Minimal shunting/asymptomatic = none If pulmonary circulation = 1.5 - 2 x systemic blood flow - SURGICAL CLOSURE is indicated (prevents development of pulm HTN) |
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What is the incidence of PDA? |
1:2500 live births |
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Consequences of PDA |
L-R shunting -pulmonary HTN -left ventricular overload -CHF (significant increase in PVR can reverse flow) -cause hypoxia |
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Treatment of PDA |
Pharmacologic - indomethacin, toradol Surgical ligation |
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Intervention for R-L shunt through PDA |
Increase afterload (phenylephrine) Close shunt (indomethacin, toradol) pulm vasodilation???? |
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When would it be advantageous to keep a PDA open? How is this done (and anesthetic implications)? |
Some forms of congenital heart disease (Tetrology of Fallot), interrupted aortic arch, transposition of great arteries, pulmonary atresia, pulmonary stenosis. Ductus arteriosus supplies most of pulmonary blood blow. -Keep open with PGE1 (alprostadil) - direct acting vasodialator. -Continuous infusion. Can only shut off briefly for induction. |
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Compare the neonatal myocardium to the adult myocardium. |
Less organized/fewer myocytes -limited ability to increase contractility -reduced LV compliance -limited ability to increase SV -CO increased by increasing HR |
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Because of limited LV compliance in neonates. Small chanes in end diastolic volume produce ____________ |
large changes in end diastolic pressure |
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Compare cardiac reserve of neonates to adults |
Resting cardiac output is close to maximal -mature heart can increase CO by 300% -neonatal heart can increase CO by 30-40% *neonates do tolerate hypoxia better compared to adults (greater glycogen stores) ???? -or myoglobin |
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What medication would you give to increase neonatal cardiac output? |
Atropine - to increase HR |
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Compare the sympathetic and parasympathetic nervous system of the neonate. What does this predispose neonates to? |
SNS = sparse (fully developed at 6 mo.) PNS = fully developed at birth Bradycardia |
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Describe the baroreceptor response in neonates? |
Immature Significantly depressed by anesthetics Limited response in neonates |
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Describe the arterial chemoreceptor response in neonates. |
Opposite that of adults Response to hypoxia is bradycardia |
