Pediatric Anesthesia Quiz #3 Flashcards
(120 cards)
1
Q
During fetal circulation, PVR is ____ and SVR is ____.
A
- high
- low
2
Q
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.
A
- decreases
- increases
3
Q
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.
A
- pressure changes
- reduced levels of prostaglandins
4
Q
Define a Left-to-Right shunt
A
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
5
Q
Define a Right-to-Left shunt
A
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
6
Q
What are two of the “simple” Left-to-Right shunts?
A
- ASD(Atrial septal defect)
- VSD)Ventricular septal defect)
Increased Pulmonary Blood Flow
7
Q
What is one of the “simple” Right-to-Left shunt?
A
-TOF(Tetrology of Fallot)
Decreased Pulmonary Blood Flow—>Cyanosis
8
Q
What are three of the complex shunts?
A
- TGA)Transposition of the great arteries)
- Truncus arteriosus
- HLHS)Hypoplastic left heart syndrome)
Mixing of Pulmonary and Systemic Blood flow with Cyanosis
9
Q
What hemodynamic alteration may worsen(increase flow through) a left-to-right intracardiac shunt?
A
- 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.
10
Q
The most common congenital heart defect in children is _____?
A
-VSA—>20% of CHD in children
11
Q
ASD/VSD are both examples of _______ shunts.
A
Left-to-Right Shunt
12
Q
What are the characteristics of an Atrioventricular Septal Defect?
A
- ASD and a VSD
- causes a Left-to-Right shunt
- single common atrioventricular valve
13
Q
What is a patent ductus arteriosus? When does the ductus arteriosus normally close?
A
- 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
14
Q
Name the physiologic factor most responsible for closure of the ductus arteriosus after birth.
A
- 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.
15
Q
Is the shunt of a patent ductus arteriosus right-to-left or left-to-right?
A
-The shunt is left-to-right.
16
Q
With a patent ductus arteriosus, what cardiovascular changes occur?
A
- 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.
17
Q
What is Persistent Pulmonary Hypertension(PPHN) of the Newborn?
A
- 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)
18
Q
List 6 factors that contribute to persistent pulmonary hypertension of the newborn(PPHN).
A
- hypoxia
- acidosis
- hypothermia
- hypovolemia
- pneumonia
- inflammatory mediators
PVR follows pCO2—> think high pCO2 = high PVR
19
Q
Identify conditions and risks that precipitate persistent pulmonary hypertension(PPHN) of the newborn.
A
- 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)
20
Q
What is the probable problem if the pediatric patient has a systolic and a diastolic murmur?
A
- Patent ductus arteriosus
- A continous systolic and diastolic murmur is often the only manifestation of patent ductus arteriosus.
21
Q
What are the characteristics of a PDA Ligation?
A
-closure of the PDA via thoracotomy, often done in the NICU with extremely-low birth weight neonates(
22
Q
Where are pulse oximeters placed on the neonate to monitor predicate and post ductal oxygenation?
A
- 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.
23
Q
If the pulse is lost from the lower limb(post ductal) during a test clamping of the duct, this might indicate that……?
A
-the aorta has been clamped inadvertently.
24
Q
What is the purpose of a predicate oximeter in the neonatal patient undergoing cardiac surgery?
A
- 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.
25
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)
26
Right-to-Left shunts in the neonatal circulation is a result of.......?
-obstructed pulmonary blood flow/Pulmonary stenosis
ROAD BLOCK TO THE LUNGS
27
TOF(Tetrology of Fallot) is the most common _____ CHD and account for _______ of CHD.
- cyanotic
| - 6-11%
28
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
29
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
30
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.
31
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)
32
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.
33
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.
34
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
35
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.
36
List three congenital defects in which there is a right-to-left shunt.
1. Tetrology of Fallot(TOF)
2. Pulmonary atresia with VSD
3. 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)
37
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.
38
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%)
39
Dual patency is maintained after birth with(2):
1. prostaglandin E1 infusion
| 2. balloon atrial septostomy is performed urgently in neonatal period.
40
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
41
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.
42
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.
43
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
44
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
45
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
46
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
47
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)
48
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%
49
What are some anesthesia-related considerations for HLHS-Norwood?
- high dose opioid technique
- venous access via femoral or umbilical vein--->avoid internal jugular vein for future Glenn shunt
- post op myocardial dysfunction is common
- balancing SVR and PVR after CPB is difficult, often a combination of Milrinone/Epi/Dopamine
- sternum remains open for several days post-op
50
At what age is the Bi-directional Glenn shunt placed?
The Glenn operation takes place at about 6 months of age
51
What are the characteristics of the Bi-directional Glenn shunt?
- the BT shunt is taken down and a new connection is created from the SVC to the PA
- the result is a pulmonary blood supply that is provided by systemic venous blood from the SVC---> flow is passive and dependent on pulmonary arterial pressures
- the infant remains cyanotic with arterial saturations in the mid-80's because desaturated blood from the IVC continues to flow into the heart and systemic circulation
52
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
53
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
54
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)
55
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%
56
What are some anesthesia-related considerations for HLHS-Norwood?
- high dose opioid technique
- venous access via femoral or umbilical vein--->avoid internal jugular vein for future Glenn shunt
- post op myocardial dysfunction is common
- balancing SVR and PVR after CPB is difficult, often a combination of Milrinone/Epi/Dopamine
- sternum remains open for several days post-op
57
At what age is the Bi-directional Glenn shunt placed?
The Glenn operation takes place at about 6 months of age
58
What are the characteristics of the Bi-directional Glenn shunt?
- the BT shunt is taken down and a new connection is created from the SVC to the PA
- the result is a pulmonary blood supply that is provided by systemic venous blood from the SVC---> flow is passive and dependent on pulmonary arterial pressures
- the infant remains cyanotic with arterial saturations in the mid-80's because desaturated blood from the IVC continues to flow into the heart and systemic circulation
59
What are the characteristics of the HLHS-Fontan?
- involves connecting the IVC to the PA via extracardiac or intracardiac conduit to create a single-ventricle circulation(Fontan)
- the single RV pumps blood to the systemic circulation while the pulmonary blood supply is provided by PASSIVE FLOW from the SVC and IVC
- it is essential that PVR remains low.....any increase in PVR will dramatically reduce pulmonary blood flow and eventually reduce cardiac output
- it is common for a small howe(i.e., fenestration) to be created between the extra cardiac conduit and the RA so that if the PVR rises, blood will be directed to the RA and allow cardiac output to be maintained-a much safer situation than a state of low CO
- long term, these children need heart transplantation d/t RV(the only functional ventricle) failure over time
60
What are postop HLHS-Fontan considerations?
- PVR must remains low post operatively, careful management of lungs is important to minimize atelectasis and nitric oxide is occasionally required
- if an interpose is required, milrinone is a good choice because of its beneficial effects on PVR
- early extubation is beneficial in terms of hemodynamics
61
What effect does hypoxia have on pulmonary vascular resistance?
- hypoxia causes pulmonary vasoconstriction but causes systemic vasodilation
- hypoxia and acidosis are potent stimuli for increases in PVR
62
High FiO2 will cause an ______ in PVR and potentially _____ blood flow towards the lungs and ______ systemic circulation.
- decrease
- increase
- away
63
In HLHS patients, excessive blood flow to the lungs resulting from a low PVR and a relatively high SVR results in........and leads to........?
- steals blood from the systemic circulation
- leading to hypotension, myocardial ischemia and progressive acidosis
*It is dangerous to administer high FiO2 to an HLHS patient*
64
HLHS anesthesia considerations:
If PVR decreases...what happens?
If PVR increases...what happens?
- If PVR decreases, BF will be directed away from the systemic circulation and the lungs will be flooded--->hypotension, hypo perfusion and acidosis
- If PVR increases, BF will be directed away from the lungs and cyanosis will increase
65
What are a couple of anesthesia considerations to employ with HLHS patients?
- keep neonate spontaneously breathing with FiO2 of ~21% and Prostaglandin E1 infusion to maintain ductal potency(to keep PDA open)
- maintain a normal/high PaCO2
66
What is the role of prostaglandins in the neonate?
- Prostaglandins are naturally occurring hormone-like substances that circulate in the fetus' bloodstream and keeps the ductus arteriosus(PDA) open
- After birth: decreased prostaglandin production plus increased oxygen tension will close the ductus arteriosus
67
If you want to maintain a patent ductus arteriosus(PDA)---->?
If you want to close a patent ductus arteriosus(PDA)--->?
- give prostaglandins
| - give Indomethacin or PDA ligation
68
Prostaglandin E1 maintains potency of the ductus arteriosus in infancy when the body is supplied by Right-to-Left ductal flow, as in cases of..........
interrupted aortic arch, critical aortic stenosis and HLHS
69
Conversely, the PDA can supply pulmonary blood flow form the aorta in lesions such as.......
pulmonary atresia, tricuspid atresia and severe Tetrology of Fallot
70
How do potent volatiles affect SVR as compared to PVR?
they reduce SVR more than PVR
71
PVR is decreased by.......
- PVR is decreased by an increase in FiO2(100%) and hyperventilation to pH of 7.6
- decreased ETCO2 causes a decrease in PVR
72
PVR is increased by.....
PVR is increased with PEEP, acidosis, hypothermia and low FiO2(30% or less)
73
Phenylephrine ____ SVR > than PVR----> can be used in the OR to......
Phenylephrine increases SVR more than PVR and can be used in the OR to reduce R-to-L shunt and increase L-to-R shunt
74
7 factors known to INCREASE PVR?
1. hypoxemia
2. hypercapnia(increased ETCO2 causes an increased PVR)
3. acidosis
4. hypothermia
5. atelectasis
6. transmitted positive airway pressure
7. stress response/stimulation/light anesthesia
75
What are the characteristics of Aortic Stenosis in the neonate?
- increasing imbalance between oxygen demand and supply=impaired coronary BF d/t low coronary perfusion pressures and increased workload on the LV leading to subendocardial ischemia, LV hypertrophy and the risk of LV failure
- risk of sudden death, especially the younger infants(first 3 months life)--->Urgent valvuloplasty(transluminal balloon angioplasty in cath lab)
76
Anesthesia considerations of Aortic Stenosis:
| Most important is the balance oxygen supply and demand. 3 ways of doing that?
1. Maintain normal HR(avoid tachycardia and bradycardia)
2. Maintain SVR to preserve coronary perfusion
3. Avoid HTN and myocardial depression
77
What 4 category of CHD patients are considered HIGHEST RISK of adverse outcomes resulting from SBE?
1. completely repaired cyanotic CHD patient with prosthetic material/device placed within the past 6 months
2. Un-repaired, cyanotic CHD patient with palliative shunt/conduit
3. Cardiac transplantation recipients with cardiac valvular disease
4. CHD patient with history of endocarditis
78
What type of procedures should HIGHEST RISK CHD patients receive antibiotics prior to and which not?
- abx for dental procedures(including manipulation of gingival tissue, periodical region of teeth or perforation of oral mucosa), and procedures involving the respiratory tract, infected skin, tissue just under the skin, and musculoskleletal tissue.
- no abx prior to GI/GU procedures
79
What is the inhaled induction agent of choice for pediatric cardiac anesthesia? At what MAC can cause slowing of HR and res depression?
- Sevo
| - >1.5 MAC
80
How do CHD patients respond to a slow HR?
with reduced CO, hypoventilation, hypercarbia, hypoxia and a rise in PVR
*Sevo causes a mild decrease in SVR*
81
Which CHD patients tolerate carful induction with Sevo? How should severe CHD patients be induced?
- the mild to moderate CHD patients
| - young infants with severe CHD:IV induction with high opioid does(3-5mcg/kg Fentanyl or more) with low dose sevo/iso
82
How does Iso and Halothane compare to Sevo?
- Iso similar characteristics to Sevo, but has a pungent odor so not used as an inhalation agent) also has a higher incidence of laryngospasms
- Halothan(not available in US) very rapid uptake of Hal....can cause significant hypotension, arrhythmias and brady(infants do not tolerate it well)
83
Can N2O be used as an anesthetic agent with pediatric CHD?
- 70% nitrous is ok for induction, but should be avoided as maintenance because of risk of intravascular air emboli and the potential increase in PVR
- It mildly decreases CO in infants and should be avoid in children with limited pulmonary BF and pulmonary HTN and depressed myocardial funciton
84
In what disease process would ketamine need to be avoided and why?
-poor choice if tachycardia is undesired such as in Aortic stenosis or where catecholamine stimulation is already maximized(severe cardiomyopathy)
85
What is the IV dose of ketamine?
1-2 mg/kg
good analgesic agent which increases HR, BP and CO by stimulating the release of endogenous catecholamines
86
Although etomidate is a great short-acting induction drug which has favorable hemodynamic profile with little effect on BP, HR or CO...what are two things associated with it that should be monitored?
1. increased mortality with continuos etomidate infusion d/t adrenal suppression
2. inhibition of steroid syntheses can occur after a single dose
87
Characteristics of propofol with CHD?
- induction causes decrease in SVR, BP and CO with variable effects on HR
- it is generally avoided as an induction agent in severe CHD children because of its effects on SVR and BP
- Avoid propofol in patients with fixed CO(severe or mitral stenosis)-severe hypotension
- use propofol/dexmedtomdine infusion during CPB to reduce risk of awareness
88
Can fentanyl and Sufentanil be used in pediatric cardiac anesthesia?
- fentanyl provides excellent hemodynamic stability with suppression of the hormonal and metabolic stress response, however patient probably remains intubated
- often combined with High-dose fentanyl, midazolam, pancuronium with low-dose Sevo/Iso
- Sufentanil: 5-10 times more potent than fentanyl, has a large margin of safety
89
Will a left to right intracardiac shunt theoretically slow or accelerate IV induction? Why is this phenomenon rarely evident clinically?
-IV induction should be slowed by the left to right shunt; however, unless cardiac output is very poor, the effect is clinically irrelevant.
90
Will a left to right intracardiac shunt theoretically slow or accelerate inhalation induction? Why is this phenomenon rarely evident clinically?
- A left to right intracardiac shunt should accelerate the speed of inhalation induction because the rate of transfer of anesthetic agent from the lungs to the blood is increased
- However, this effect is rarely clinically evident because decreased delivery of anesthetic to the target tissues negates the increased intake of agent with the left to right intracardiac shunt
91
Will a right to left intracardiac shunt theoretically slow or accelerate an IV induction?
An IV induction will be theoretically accelerated with a right to left intracardiac shunt
92
Will a right to left intracardiac shunt theoretically slow or accelerate inhalation induction? Is the effect clinically significant?
- A right to left intracardiac shunt will theoretically slow inhalation induction, because less anesthetic is absorbed from the lung, and mixing will further dilute blood passing to the left, decreasing the arterial concentration of the blood going to the brain, especially the less soluble agents
- This effect is rarely problematic
93
A right to left intracardiac shunt is present in the patient with VSD with Eisenmenger's syndrome. What hemodynamic alterations may worsen(increase shunt flow) the right to left shunt of VSD with Eisenmenger's syndrome?
- An abrupt increase in PVR or decrease in SVR is poorly tolerated in the patient with VSD
- Avoid interventions that may increase PVR or decrease SVR in the patient with right to left intracardiac shunting.
94
What is the anesthetic concern for a pediatric patient undergoing repair of a VSD with significant pulmonary HTN?
- The patient with an unprepared VSD and irreversible pulmonary HTN often displays right to left shunting through the VSD(Eisenmenger's physiology).
- Manipulations that may increase PVR can cause rapid deterioration and include hypoxia, hypercarbia, acidosis, hypothermia, atelectasis, sympathetic stimulation and polycythemia.
- Early closure of VSD before 1 year old results in normal ventricular function and EF.
95
What is the anesthetic concern for the pediatric patient undergoing repair of a VSD without significant pulmonary HTN?
-VSD without significant PHTN should be managed to avoid arrhythmias, RV dysfunction, pulmonary vascular obstructive disease and paradoxical embolus
96
Which two sites are to be avoided when obtaining arterial blood gases in the neonate and why?
- Brachial--->nerve damage
| - Femoral--->femoral head necrosis and limb shortening
97
Identify the BEST site to obtain ABGS from the neonate?
- ABG in the neonate are best obtained from the radial artery
- In addition to the ease of access, this site will reflect predicate oxygen saturation, which better reflects cerebral oxygenation.
98
Should upper extremity blood pressure be monitored in the neonate with preductal coarctation of the aorta on the right or left arm?
Monitoring of blood pressure is best achieved in a patient with predicate coarctation by placing a catheter in the right radial artery.
99
To what do pre-ductal or post ductal coarctation of aorta refer?
- Coarctation of the aorta refers to a discrete narrowing of the aorta immediately distal to the origin of the left subclavian artery
- A pre-ductal coarctation refers to a coarctation in a neonate or infant in which the narrowing occurs proximal to the opening of the ductus arteriosus
- Post ductal coarctations supposedly present in adulthood long after closure of the ductus arteriosus.
100
List three conditions that increase right to left shunting(Tetrology of Fallot)
- Acidosis, hypercarbia and hypotension(decrease in SVR) increase right to left shunt.
- In general, increases in PVR or decreases in SVR(caused by acidosis or hypercarbia) increase right to left shunting.
- Volatile anesthetics and histamine release decreases SVR.
101
What change in SVR and PVR increase shunt in the Tetrology of Fallot patient? What drugs increase shunt in the patient with TOF by altering SVR or PVR?
- Shunt increases when SVR decreases or PVR increases
- Volatile anesthetics, drugs that release histamines, ganglionic blockers, alpha blockers or other vasodilators(nitride) decrease SVR, increase right to left shunt, and worsen arterial hypoxemia
- Increased PVR increases shunt in a child with cyanotic heart disease
- N2O increases PVR, which is detrimental to children with right to left shunts
102
During the case, oxygen saturation decreases, apparently because of increased shunting. The patient has TOF, what agent might be selected to decrease shunt and increase oxygen saturation?
- Intravascular fluid volume must be maintained with IV fluid administration since acute hypovolemia will ten to increase the magnitude of the right to left intracardiac shunt.
- An alpha-agonist drug such a phenylephrine must be promptly available to treat an undesired decrease in systemic blood pressure caused by a decrease in SVR
103
An infant has Tetrology of Fallot(cyanotic heart disease), which of the following ABG parameters will NOT typically be changed: PaO2, PH, PaCO2?
- pH and PaCO2 are likely to be in the normal range.
| - PaO2 is usually markedly decreased(
104
What are the goals of anesthetic management for the patient who has Tetrology of Fallot?
- The goals should be to maintain intravascular volume and SVR
- Increases in PVR also should be avoided.
105
List four congenital heart defects involved with Tetrology of Fallot(cyanotic heart disease)?
1. VSD
2. Right ventricular outflow tract obstruction(pulmonary stenosis)
3. RV hypertrophy
4. Overriding aorta-dextropositon(to the right) of the aorta with overriding of the VSD
106
What is an Atrioventricular canal repair?
a patch closure of atrial and ventricular communication to eliminate the intracardiac shunt
107
What is a PA banding?
a constrictive band placed around main PA to limit excessive Pulmonary BF
108
What is a Valvectomey?
valve excision
109
What is a Valvotomy?
opening of a stenotic valve
110
What is a Valvuloplasty?
a valve repair
111
What is the general anesthetic typically required for an ablation?
- The ablation required mapping and precise ablation of the aberrant pathway. During the ablation, unexpected movement may result in catheter dislodgment and damage to normal conducting tissue; therefore, GA is usually required in younger children.
- Anesthetic agents and techniques should be chosen to maintain circulating catecholamines and avoid suppression of arrhythmogenesis,f or identifying aberrant pathways.
- Isuprel is used to introduce tachyarrhythmias during mapping.
- Generally avoid medications that will ameliorate the dysrhythmias or slow down the tachyarrhythmias i.e. lidocaine, opioids, volatiles
- inhaltion inductionis ok, however convert to propofol infusion as maintenance
- treat hypotension with IVF and void phenylephrine...severe hypotension maybe treated with vasopressin
112
What are the characteristics of Flolan?
- naturally occurring prostaglandin
- Potent vasodilator(SVR and PVR)
- TX: primary pulmonary HTN(PPHN)
- bronchodilation
- Inhibition of platelet aggregation
113
How is Flolan metabolized? What are some common SE and what are the contraindications of Flolan?
- Rapid metabolism via enzymatic degradation(HL 6 minutes!)
- SE: flusing, HA, N/V, hypotension
- Contraindications: CHF d/t sever LV systolic dysfunction
*avoid abrupt interruption of Flolan IV--->rebound PHTN(don't use the PIV through which Flolan is infusing for induction)*
Very minute increments of dosage: nanogram/kg/min
114
By what mechanisms does nitric oxide produce pulmonary vascular smooth muscle relaxation?
- Very specific pulmonary vasodilator with minimal effects on systemic circulation.
- Acts on guanylate cyclase to produce pulmonary vascular smooth muscle relaxation.
115
How is NO used in the cath lab?
used to assess reactivity of pulmonary vasculature to vasodilation in children with pulmonary HTN versus fixed pulmonary vascular obstructive disease. It facilitates operative planing and management.
116
What is the dosages of NO?
NO is administered in 1-80 PPM(usually 20-40)
*blood methemoglobin {} needs to be checked in long-term use*
117
How do children exhibit different pharmacokinetics from adults?(4 ways)
1. Lower protein binding(more free drug=greater effect)
2. Larger volume of distribution("jellyfish)-require larger loading dose of WATER SOLUBLE meds to achieve clinical effect
3. Smaller proportion of fat and muscle stores(less redistribution into muscle/fat mass=large initial blood concentration)
4. Immature renal and hepatic function(less metabolism & elimination)
118
What drugs will have a larger volume of distribution in the infant compared with the adult?
What drugs will have a smaller volume of distribution in the infant compared with the adult?
- The infant's extracellular body fluid compartment is large compared to the adult, so WATER-SOLUBLE DRUGS will have a LARGER VOLUME OF DISTRIBUTION IN THE INFANT compared with the adult
- Conversely, LIPID-SOLUBLE DRUGS will have a SMALLER VOLUME OF DISTRIBUTION IN THE INFANT compared with the adult
119
Some medications may displace bilirubin from its protein binding sites and possibly predispose an infant to ______?
kernicterus
120
Neonates require a higher dose of succinylcholine than adults because of these two reasons:
1. Neonates have a LARGER VOLUME OF DISTRIBUTION than adults(40-50% BW of neonates is extracellular fluid whereas in the adult extracellular fluid is only 20-25% BW--->Succ distributes in the EC volume so more drug is needed on a per kg basis
2. Neonates have immature neuromuscular junctions(they are less sensitive or more resistant to its neuromuscular effects)more Succ is needed to compete with the ACh at the NMJ(neonates require twice as much succ on a BW basis than older children or adults)
