Pediatric Anesthesia Quiz #3 Flashcards
During fetal circulation, PVR is ____ and SVR is ____.
- high
- low
After birth, the neonate takes its first breaths, the lungs inflate and PVR_____. While the placenta is disconnected and blood is not “draining back into the mother”, SVR ____. With these pressure changes blood flow easier into the lungs and becomes oxygenated.
- decreases
- increases
The increased pressure in the aorta allows some “back flow” of blood via the ductus arteriosus back into the pulmonary artery which causes additional oxygenation of the blood. Eventually, the _________ within the two circulation and the __________ causes the closure of the ductus arteriosus and former ovale within days after birth.
- pressure changes
- reduced levels of prostaglandins
Define a Left-to-Right shunt
due to higher pressures in the left heart, blood flows back to the right heart via ASD/VSD, causing increased blood flow in the lungs = pulmonary congestion –> pulmonary HTN
Define a Right-to-Left shunt
blood bypasses the lungs because of an obstruction of the lungs(pulmonary stenosis)=blood flows through ASD/VSD or both to the systemic side = cyanosis
What are two of the “simple” Left-to-Right shunts?
- ASD(Atrial septal defect)
- VSD)Ventricular septal defect)
Increased Pulmonary Blood Flow
What is one of the “simple” Right-to-Left shunt?
-TOF(Tetrology of Fallot)
Decreased Pulmonary Blood Flow—>Cyanosis
What are three of the complex shunts?
- TGA)Transposition of the great arteries)
- Truncus arteriosus
- HLHS)Hypoplastic left heart syndrome)
Mixing of Pulmonary and Systemic Blood flow with Cyanosis
What hemodynamic alteration may worsen(increase flow through) a left-to-right intracardiac shunt?
- an increase in systemic vascular resistance(SVR) may increase left-to-right intracardiac shunt flow, such as occurs in atrial septal defect.
- avoid interventions that may increase SVR in the patient with an ASD.
The most common congenital heart defect in children is _____?
-VSA—>20% of CHD in children
ASD/VSD are both examples of _______ shunts.
Left-to-Right Shunt
What are the characteristics of an Atrioventricular Septal Defect?
- ASD and a VSD
- causes a Left-to-Right shunt
- single common atrioventricular valve
What is a patent ductus arteriosus? When does the ductus arteriosus normally close?
- Patent ductus arteriosus is an abnormal persistence in the newborn of blood flow through the ductus arteriosus, an opening between the pulmonary artery and the aorta.
- Normally, the ductus closes with a few hours to a few days after birth due to changes in the pressures of the pulmonary vasculature
Name the physiologic factor most responsible for closure of the ductus arteriosus after birth.
- Normal closure of the ductus arteriosus occurs in response to INCREASED ARTERIAL OXYGEN TENSION(PaO2), as well as to reduction in circulating prostaglandins that follow separation of the placenta.
- Realize that a number of other substances such as eicosanoids and factors such as PaCO2 and pH have been implicated, but that increased oxygen tension seems to be the major factor precipitating ductus arteriosus closure.
Is the shunt of a patent ductus arteriosus right-to-left or left-to-right?
-The shunt is left-to-right.
With a patent ductus arteriosus, what cardiovascular changes occur?
- A patent ductus arteriosus allows blood to flow from the aorta into the pulmonary after(PA).
- The additional blood is deoxygenated in the lungs and returned to the LA and the LV and this causes increased workload on the left side of the heart and LV hypertrophy, and increased pulmonary vascular congestion and resistance.
- Most patients are asymptomatic.
What is Persistent Pulmonary Hypertension(PPHN) of the Newborn?
- is typically a term or late-preterm neonate who does not have associated congenital anomalies and presents within hours of birth with severe respiratory failure that requires intubation and ventilation
- it is a result of an abnormal early adaption to the neonatal circulation.
- is also called persistent fetal circulation
- is associated with substantial infant morbidity & mortality(10-20%)
- characterized by a sustained 1. elevation of PVR, 2. decreased perfusion of the lungs, and 3. continued R-to-L shunting of blood through the fetal channels(foramen ovale and ductus arteriosus-resulting in cyanosis)
List 6 factors that contribute to persistent pulmonary hypertension of the newborn(PPHN).
- hypoxia
- acidosis
- hypothermia
- hypovolemia
- pneumonia
- inflammatory mediators
PVR follows pCO2—> think high pCO2 = high PVR
Identify conditions and risks that precipitate persistent pulmonary hypertension(PPHN) of the newborn.
- PPHN is usually caused by precipitating conditions such as severe birth asphyxia, meconium aspiration, sepsis, congenital diaphragmatic hernia, and maternal use of NSAIDs.
- Risk factors for PPHN include maternal diabetes, asthma and cesarean delivery.
(NSAIDs may cause premature constriction of the ductus arteriosus in the fetus and thus predispose to PPHN)
(it is believed that labor with vaginal delivery increases endogenous prostaglandin and catecholamines which promotes clearance of fetal lung fluids, which might not be achieved with a C-section. Moreover, the physical compression that results from normal vaginal delivery, which expels fetal lung and airway fluid, is lacking in infants who are born via C-section.)
(Maternal BMI and diabetes as risk factors for PPHN: both obesity and insulin resistance are known to induce endothelial dysfunction and inflammation and might have a direct impact on fetal development. Maternal diabetes increases the prevalence of macrosomia(large fetus) which often results in a C-section)
What is the probable problem if the pediatric patient has a systolic and a diastolic murmur?
- Patent ductus arteriosus
- A continous systolic and diastolic murmur is often the only manifestation of patent ductus arteriosus.
What are the characteristics of a PDA Ligation?
-closure of the PDA via thoracotomy, often done in the NICU with extremely-low birth weight neonates(
Where are pulse oximeters placed on the neonate to monitor predicate and post ductal oxygenation?
- Preductal oxygenation should be measured with a pulse oximeter on the right hand or finger.
- Postductal oxygenation should be measured with a pulse oximeter on the left foot or toe.
If the pulse is lost from the lower limb(post ductal) during a test clamping of the duct, this might indicate that……?
-the aorta has been clamped inadvertently.
What is the purpose of a predicate oximeter in the neonatal patient undergoing cardiac surgery?
- Measurements of arterial oxygen saturation taken at a PRE DUCTAL location(right hand/finger) are a better index of the NEONATAL CEREBRAL OXYGENATION than are those taken at a post ductal location(left foot/toe)
- The right-to-left shunts at the ductus arteriosus persists for some time after birth and this shunt may affect oxygen saturation readings, thus predicate placement of the pulse oximeter is preferred.
- A post ductal pulse oximeter may be used in addition to the pre ductal pulse oximeter to quantitate the severity of the right-to-left shunt.
Where should arterial blood pressure be measured in a patient undergoing repair of a PDA?
-the catheter for measuring blood pressure fouls be placed in the peripheral artery such as the femoral(POST DUCTAL)
Right-to-Left shunts in the neonatal circulation is a result of…….?
-obstructed pulmonary blood flow/Pulmonary stenosis
ROAD BLOCK TO THE LUNGS
TOF(Tetrology of Fallot) is the most common _____ CHD and account for _______ of CHD.
- cyanotic
- 6-11%
What are 5 characteristics of TOF?
- Right-to-Left shunting resulting in cyanosis
- VSD
- RV-Outlet Tract obstruction/stenosis
- Overriding aorta=aorta is displaced to the right so that it appears to arise from both ventricles and straddles the VSD
- RV hypertrophy
What are “get spells”?
- hypercyanotic spells that occur when there is an increase in Right-to-Left shunting
- the degree of hypoxemia depends on the relationship between RVOTO(RV-outlet tract obstruction) and SVR that determines the degree of Right-to-Left shunting
Children with TOF exhibit bluish skin during episodes of crying and feeding. What causes the “tet spells”?
-The cause is unclear, but they occur during crying, feeding or during anesthesia/surgical stimulation, metabolic acidosis, increased PaCO2 and circulating catecholamines.
How to treat TOF-hypercyanotic “spells”?(6)
- 100% oxygen
- hyperventilation(decreases ETCO2 & PVR)
- increase preload(IVF)-give fluid deficit early or give bolus of 10ml/kg crystalloid
- Sedation
- vasoconstriction with Phenylephrine(increases SVR to reverse R-L shunt)
- beta blocker to relax infundibular spasm and reduce HR(in moderation)
What are the surgical trends in TOF repair?
- surgical trend goes toward early, complete repair which involves closure of VSD and relief of RVOTO
- Modified Blalock-Taussig(BT) Shunt to improve system-to-pulmonary shunt(from subclavian artery to PA) and to improve pulmonary blood flow.
What are 4 anesthetic considerations for a TOF repair?
- Pre-sedate to prevent crying on induction, increased risk of “get spell” during induction/surgery
- place a-line on arm opposite to the side of subclavian anastomosis, because subclavian artery is going to be clamped
- snug ETT with NO air leak-lung retraction makes ventilation difficult
- prepare for blood transfusion-potential bleeding after clamp release.
Post-op pulmonary blood supply is predominantly dependent on size of BT shunt: If BT shunt is too small —>? If BT shunt is too large —>?
- If BT shunt is too small —> low saturations
- If BT shunt is too large —> infant may develop heart failure/pulmonary edema
- TEE intra-op will assess RV function
Pulmonary blood flow also dependent on SBP: the greater the BP, the more blood flow towards the lungs —> higher saturation
Does blood shunt right-to-left or left-to-right through the VSD in Tetrology of Fallot(cyanotic heart disease)?
Blood shunts R-to-L, permitting unoxygenated blood to mix with oxygenated blood, resulting in cyanosis.
List three congenital defects in which there is a right-to-left shunt.
- Tetrology of Fallot(TOF)
- Pulmonary atresia with VSD
- Patent foramen ovale
- With TOF and pulmonary atresia with VSD—>the road block causes blood to shunt R-to-L
- With PFO the shunt can reverse depending on which side of the heart the pressure is highest. If SVR is > PVR—->L-to-R shunt(with increased pulmonary blood flow, pulmonary congestion, PHTN). If PVR is > than SVR—>R-to-L shunt(bypassing the lungs=cyanosis)
What pharmacologic agent decreases a right-to-left shunt?
- a decrease in the magnitude of a right-to-left shunt occurs if SVR increases
- Phenylephrine increases SVR and decreases a R-to-L shunt.
What are the characteristics of Transposition of the great vessels(TGA)?
- the aorta arises from the Right ventricle, and the pulmonary artery arises from the left ventricle
- the coronary arteries are shown arising from the aorta
- Parallel circulation so no oxygen mixing—> two circulations run parallel rather than in series
- these children are cyanosed.
- some mixing of oxygenated blood occurs through the PDA or VSD(present in 25%)
Dual patency is maintained after birth with(2):
- prostaglandin E1 infusion
2. balloon atrial septostomy is performed urgently in neonatal period.
What are the characteristics of the “Arterial Switch”?
- the PA is moved anterior to the aorta
- the aorta is connected to the left ventricle(LV)
- the pulmonary artery is connected to the right ventricle(RV)
- the coronary arteries are connected to the neb-aortic root=most crucial part of successful outcome of arterial switch operation
In Transposition of the Great Arteries, the “Arterial Switch” operation is preformed when?
often required early at age 2-3 weeks. If untreated, pt will die within 1 year d/t hypoxia and heart failure. If fully repaired, children can expect a normal life.
What are the increased risk post-CPB with the “Arterial Switch”?
-an inherently poor LV, poor myocardial protection, poor coronary transference, coronary air, pulmonary HTN, avoid LA dilation(careful with fluid boluses), milrinone.
What are the characteristics of Truncus arteriosus?
- Complex shunt—>mixing of Pulmonary and Systemic Blood flow with Cyanosis
- common tranquil valve and mixing of oxygenated and deoxygenated blood
- rare congenital heart defect(1% of CHD)
- COMMON ARTERIAL OUTLET FOR AORTA & PA ASSOCIATED WITH SINGLE VALVE AND VSD
- Mixed blood at arterial level with high pulmonary BF —> heart failure and pulmonary HTN
- Early surgery to separate pulmonary from systemic circulation and close VSD with valved conduit
- Post op mortality is high(5-25%) d/t potential tranquil valve stenosis, coronary abnormalities, pulmonary hypertensive crisis and low birth weight
What are the characteristics of Double Outlet Right Ventricle?
- Complex shunts—> mixing of Pulmonary and Systemic Blood flow with Cyanosis
- 1% of CHD
- Both great arteries(PA and aorta) arise from the morphologic RV, often with large VSD
- Trisomy 13 and Trisomy 18 are associated with DORV
- If pulmonary stenosis(50%) is present, DORV resembles the physiology of TOF
What are the characteristics of Hypoplastic Left Heart Syndrome?
- very small LV
- mitral & aortic valve stenosis/atresia
- hypoplastic(small) aortic arch
- PULMONARY BLOOD FLOW FROM LA VIA ASD TO RA/RV
- SINGLE VENTRICLE(RV)
- SYSTEMIC BLOOD FLOW FROM RV TO PA TO AORTA VIA PDA
At birth how do the neonates present with Hypoplastic Left Heart Syndrome?
- tachypnea
- tachycardia
- cyanosis
- systolic mumur
The left side of the heart is underdeveloped
There are a series of surgeries utilized to convert Hypoplastic Left Heart into a single-ventricle type circulation. What are they?
- Norwood(Neo-aorta and BT shunt)
- Bidirectional Glenn(passive pulmonary blood flow from SVC)
- Fontan(passive pulmonary blood flow from SVC and IVC)
Describe the HLHS-Norwood.
- reconstruction of Neo-aorta in neonatal period(making a larger aorta)
- the branch pulmonary arteries are disconnected from the pulmonary trunk
- the only blood supply to the lungs is provided from either a shunt from the subclavian(using a Blalock-Taussig shunt) or from the right ventricle(Sano modification)—>both are considered PASSIVE BLOOD FLOW and is dependent on pressures.
- the child remains cyanotic(keep SpO2 70-80%
