Test 2 - Cardiovascular Physiology Flashcards
The neonatal cardiovascular system undergoes major alterations at what point?
At birth.
-Congenital heart disease often accompanies other organ system malformations
What controls the heart rate earlier in gestation than B-adrenergic control for newborns?
Parasympathetic control of heart rate matures earlier in gestation than B-adrenergic control
For a newborn, vagotonic response caused by (what medication) and opioids may lead to bradycardia or asystole, This vagal reflex can be offset by (what medication)
Succicylcholine
Atropine
Neonates may not respond to hypovolemia or an inadequate depth of anesthesia with what?
tachycardia
For fetal circulation, what organ is the prenatal respiration? What organ is excluded from fetal circulation?
- The organ of prenatal respiration is the placenta
- The lungs are excluded from fetal circulation
For fetal circulation, what are three special shunts that allow the oxygenated blood to perfuse the heart and brain?*
Ductus venosus
Foramen ovale
Ductus arteriosus
What is the fetal circulation? starting from the placenta?
Oxygenated blood returns from the placenta via the umbilical vein > ductus venosus > inferior vena cava > RA > the saturated blood crosses the foramen ovale into the LA (cerebral circulation) > the remaining RV output crosses the ductus arteriosus (systemic flow beyond the aortic arch)
For the fetal circulation, what % of RV output crosses the pulmonary circulation?
Only 10% of the RV output crosses the pulmonary circulation
For fetal circulation, 2 umbilical arteries originate from what arteries and deliver fetal blood to the placenta?
Originate from the internal iliac arteries
Unoxygenated blood***
For fetal circulation, 1 umbilical vein carries blood from the placenta to the (BLANK)
1 umbilical vein carries blood from the placenta to the FETUS
Oxygenated blood***
For fetal circulation, why is the SVR low and PVR high?
- Low SVR secondary to the low-resistance placenta
- High PVR secondary to fluid-filled lungs and hypoxic environment
With fetal circulation, what is the status of the pulmonary blood flow, LAP, and PAP?
Minimal pulmonary blood flow and low LAP
High PAP
The most oxygenated blood from the umbilical vein perfuses the brain and heart, bypassing the liver via the (BLANK) and bypassing the RV via the (BLANK)
The most oxygenated blood from the umbilical vein perfuses the brain and heart, bypassing the liver via the Decutus Venosus and bypassing the RV via the Foramen Ovale
High PVR forces most RV output across the (BLANK) into the descending aorta, allowing deoxygenated blood to return to the placenta
High PVR forces most RV output across the Ductus Arteriosus into the descending aorta, allowing deoxygenated blood to return to the placenta
With oxygen delivery for the fetal circulation, what is Maternal PaO2, umbilical vein PaO2?
- Maternal PaO2 100 mmHg
- Umbilical vein PaO2 30-35 mmHg
In the transitional circulation, the placental circulation is eliminated after the lungs do what?
The placental circulation is eliminated after the lungs expand
In the transitional circulation, the expansion of the lungs to normal FRC results in an optimal geometric relationship of the what?
Expansion of the lungs to normal FRC results in an optimal geometric relationship of the pulmonary microvasculature
In the transitional circulation, air that enters the lungs causes a marked reduction in what and increase in what?
Air that enters the lungs causes a marked reduction in PCO2 and increases PO2
When does PVR decrease for a neonate?
PVR decreases after birth
when placental cirucaltion is eliminated after lungs expand, normal FRC returns, and air enters the lungs
The LVED pressure increases enough to result in (BLANK) closure of the foramen ovale*
The LVED pressure increases enough to result in FUNCTIONAL closure of the foramen ovale
Anatomic closure of the foramen ovale takes how long?*
Anatomic closure takes months to occurs*****
Foramen ovale remains open in what % of adults?
25-30% of adults
When is the Ductus arteriosus functionally closed?**
It is functionally closed in 98% of full term infants by day 4 of life***
When is the Ductus arteriosus anatomic close?*
Anatomic closure occurs 2-3 weeks after birth**
What triggers the ductus venosus closure?
With ligation of the umbilical vein, portal pressure falls, triggering closure
How long does it take for the closure of the ductus venosus?**
This process requires more than 1-2 weeks**
At birth what are the characteristics of the RV and the LV?
At birth, the RV and the LV are similar in size and wall thickness
With the changeover from fetal circulation, the LV must do what two things?
With the changeover from fetal circulation, the LV must accommodate a greater pressure and volume workload
With the cardiac changes at birth, the LV hypertrophies in response to what? it will become twice as heavy as the RV by what age?***
- The LV hypertrophies in response to the increased workload
- Becomes twice as heavy as the RV by 6 months of age
Neonates subject to certain pathophysiologic conditions manifest severe increases in PVR, The acute load imposed on the RV may cause diastolic function and promote a what kind of shunt?
The acute load imposed on the RV may cause diastolic function and promote a right-to-left shunt via the foramen ovale
With persistent fetal circulation, if PVR exceeds SVR, what kinda of shunt may develop?
If PVR exceeds SVR, a right-to left shunt may develop via the ductus arteriosus
In persistent fetal circulation, life-theratening hypoxemia can occur, what may be required to sustain life?*
May require NO or ECMO to sustain life
Neonatal cardiovascular system has less organized (what type of cells)?
The immature myocardium has less organized myocytes
For the neonatal cardiovascular system, contractile elements constitute what % of fetal heart?
Contractile elements constitute 30% of the fetal heart vs 60% in the adult
The neonatal heart relies more on (what electrolyte) influx of the sarcolemma to initiate and terminate contraction than the adult
The neonatal heart relies more on the CALCIUM influx of the sarcolemma to initiate and terminate contraction than the adult
Neonates have diminished systolic and diastolic function due to the differences in what two things?
They have diminished systolic and diastolic function due to the differences in myocardial cell composition and calcium transport compared to adults
In the neonatal cardiovascular system, the CO is increased due to what?
The CO is increased due to a high metabolic rate in the infant
The immature neonatal heart exhibits sensitivity to pharmacologic agents that produce what two effects?
The immature neonatal heart exhibits sensitivity to pharmacologic agents that produce negative inotropic and chronotropic effects
For a neonate, when does the SNS an PNS reach maturity?
The SNS reaches maturity by early infancy and the PNS reaches maturity within a few days of birth
-Predisposes neonates to marked vagal responses
Pulmonary vascular development is incomplete after birth, when does the pulmonary vasculature mature?
Pulmonary vasculature matures during the 1st few years of life
With the pulmonary vascular development, PVR begins to decrease after birth due what two things?
PVR begins to decrease after birth due to lung expansion and oxygenation
If the neonate is subject to certain pathophysiologic conditions that lead to increased PVR, what kind of shunt may develop via the ductus arteriosus?
That can lead to what?***
If the neonate is subject to certain pathophysiologic conditions that lead to increased PVR, a R-L shunt may develop via the ductus arteriosus
_*Persistent fetal circulation
When giving anesthetics to young children you must take into account how it will affect the immature myocardium, what should you know about the inhaled anesthetics?*
All inhaled anesthetics are myocardial depressants
When giving anesthetics to young children you must take into account how it will affect the immature myocardium, what should you know about midazolam?*
Midazolam*
- Well tolerated in children with cardiac disease
- Can decrease CO when combined with morphine
When giving anesthetics to young children you must take into account how it will affect the immature myocardium, What should you know about Opioids?*
Opioids
- Used in the field of pediatrics due to their cardiovascular stability, even at high doses
- Minimal effect on HR, CO, PVR, MAP, and SVR
When giving anesthetics to young children you must take into account how it will affect the immature myocardium, What should you know about propofol?*
Propofol
Can decrease BP and HR
When giving anesthetics to young children you must take into account how it will affect the immature myocardium, What should you know about ketamine?*
Ketamine
- Its action as a sympathomimetic preserves myocardial function
- It does have depressant cardiac effects in hearts that are depleted of catecholamine’s
When giving anesthetics to young children you must take into account how it will affect the immature myocardium, What should you know about regional anesthesia?*
Regional anesthesia
- Spinal and epidurals have minimal hemodynamic effects compared with the vasodilation in adults
- Routine fluid loading is not required
- Has negligible hemodynamic effects
With congenital heart disease, 2/3 of the lesions are found in children with which genetic code?
2/3 of the lesions are found in children with trisomy 21
What is shunting?**
Process by were venous return into one circulatory system is recirculated through the arterial outflow of the same circulatory system
What is the pathophysiology of a “single ventricle”?
When there is complete mixing of pulmonary and systemic venous blood at the atrial or ventricular level.
What is the sole source of systemic blood in a patient with a “single ventricle”?
During a single ventricle the PDA (patent ductus arteriosus) is the sole source of systemic blood.
-Ductal dependent circulation.
Single ventricle can also occur when there are 2 well formed anatomic ventricles, some examples are?
- Tetralogy of fallot
- Truncus arteriosus
- Severe neonatal aortic stenosis
What is the pathophysiology of intercirculatory mixing?
Occurs in the unique situation that exist in transposition of the great arteries
