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64 Cards in this Set

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Define neonate

< 28 days

Define Infant

1 month - 1 year

Define Child

> 1 year

A neonate weighs ________ as much as an adult

1/21

Neonatal BSA is ______ as much as an adult

1/9

What are the consequences of large relative body surface area of a neonate

Higher heat loss


Higher insensible fluid loss

__________ of a neonate's body surface area is its head

20%

A neonate is ____ as tall as an adulg

1/3

An adult head is ______ of its TBSA

1/8

Describe what parallel circulation in the fetusmeans

Systemic circulation exits both the left and right sides of the heart

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)


There is ________ to ________ shunting across the ductus arteriosis and formen ovale.

Right to left

Deoxygenated blood is pumped down the fetal descending aorta in to the two ________ into the placenta

umbilical arteries

What are the two functions of the placenta

Respiratory center



Filtration (nutrients and waste)

How much aortic blood enters the placenta from the descending aorta?

50%

What percent of blood returning from the placenta bypasses the liver?




How is this accomplished?

50 percent bypasses liver via ductus venosus

A large portion of fetal blood entering the RA from the IVC is shunted directly to the LA via the ________________

foramen ovale

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

What direction does blood travel through a PFO?

Normally does not (left sided heart pressures > right sided heart pressures)

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)

Where is the highest oxygen saturation observed in the fetal circulation?

Umilical vein (70-80%)



How much of the right ventricular output flows into the pulmonary vascular blood?

5-10%

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

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

How does clamping of the umbilical cord affect circulation?

Significant increase in systemic vascular resistance.




Decrease in IVC blood flow and RA pressure

Overall affect of circulatory changes at birth:

Dec. PVR + Inc. SVR = marked increase in pulmonary blood flow and pressure in left side of heart

How does the ductus venosus close?

Ligation of the umbilical vein changes portal pressures, triggering closure of the ductus venosus.

When does the ductus venosus close?

1-3 hours after birth (functional closure)




2 weeks of life (anatomic closure)

How does the foramen ovale close?

LAP exceeds RAP (due to pulmonary and systemic changes)

When does foramen ovale close?

Functional closure soon after birth




Anatomic closure by 2-3 months of age

What can cause the Foramen Ovale to re-open

hypoxia, hypercarbia, acidosis, hypothermia




straining/coughing/vagal manuvers/bucking on ventilator

What are the consequences of right to left shunting?

Hypoxia



Embolic events (stroke, TIA, MI)



Migraines

What causes the ductus arteriosus to close?

Increased arterial oxygen tension and a reduction in circulating prostaglandins

What can cause the ductus arterosus to re-open

Hypoxia, hypercarbia, hypothermia, acidosis

When does anatomic closure of the ductus arterosus occur?

Requires 1-3 months




Thrombosis and fibrosis

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.

What causes PPHN?

Continuation or return to right to left shunting


(through FO and DA)

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...)

Who is at risk for PPHN?

Premature infants < 37 weeks




Critically ill neonates

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)

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)

Treatment of PPHN

Find and treat cause



Supportive care


-supplemental FiO2,


-hyperventilation


-maintain normal BP


-Nitric oxide, PGI2


-HFJV (oscilator), ECMO

Incidence of patent foramen ovale

50% of children less than 5




25% of adults

Can right to left shunting occur in PFO?

Yes of RAP > LAP

Consequences of right to left shunting in PFO

hypoxemia


emboli (air, thrombi) - entering systemic circulation

Can left to right shunting occur in PFO

Very rare

Treatment for PFO

If symptomatic


-reduce RA pressures (inotropes, NO)


-prevent thrombus formation (anticoagulation)


-PFO closure (surgical or percutaneous)

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

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

What is the incidence of ASD?

Most common heart defect


1:1500 live births

Normal shunt flow in ASD

Left to right


(unless RAP > LAP - i.e. pulm htn)

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)

What is the incidence of PDA?

1:2500 live births

Consequences of PDA

L-R shunting


-pulmonary HTN


-left ventricular overload


-CHF




(significant increase in PVR can reverse flow)


-cause hypoxia

Treatment of PDA

Pharmacologic - indomethacin, toradol




Surgical ligation

Intervention for R-L shunt through PDA

Increase afterload (phenylephrine)




Close shunt (indomethacin, toradol)




pulm vasodilation????

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.

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

Because of limited LV compliance in neonates. Small chanes in end diastolic volume produce ____________

large changes in end diastolic pressure

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

What medication would you give to increase neonatal cardiac output?

Atropine - to increase HR

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

Describe the baroreceptor response in neonates?

Immature


Significantly depressed by anesthetics


Limited response in neonates

Describe the arterial chemoreceptor response in neonates.

Opposite that of adults




Response to hypoxia is bradycardia