23 CONGENITAL HEART DISEASE Flashcards
1
Q
- When does shunting occur in congenital heart disease?
A
- Under normal physiologic conditions, pulmonary blood flow and systemic blood
flow do not mix, and the entire cardiac output flows in one direction. Shunting
occurs when a portion of the venous return is redirected back to the arterial
outflow of the same circulation. The shunt occurs when there is an abnormal
communication between the pulmonary blood flow and systemic blood flow.
2
Q
- What is the usual limitation to the direction and amount of shunt flow?
A
- A shunt occurs when there is an abnormal communication, or defect, between
the pulmonary and systemic circulations. The direction of the shunt flow is dictated
by the relative pressures between the communicating structures. The amount of
shunting is limited by the size of the defect
3
Q
- When does a left-to-right shunt occur?
A
- A left-to-right shunt occurs when part of the pulmonary venous return is redirected
toward the pulmonary arterial system. This can occur through anomalies in the
pulmonary veins, atrial septum, ventricular septum, or at the great vessels
4
Q
- What is the physiologic effect of a left-to-right shunt on the pulmonary blood flow
(Qp) relative to the systemic blood flow (Qs)?
A
- The physiologic effect of a left-to-right shunt is that the total pulmonary blood flow
(Qp) is greater than the systemic blood flow (Qs); that is Qp becomes greater than Qs.
This can result in hypotension and pulmonary edema.
5
Q
- What are the long-term effects of increased pulmonary blood flow that occurs in a
left-to-right shunt?
A
- Long-term effects of an increase in pulmonary blood flow, as occurs in a
left-to-right shunt, are an increase in pulmonary vascular resistance and abnormal
cardiac chamber dilation. In addition, prolonged hypotension can lead to
circulatory shock and multiple organ failure
6
Q
- Give an example of a congenital heart defect that results in a left-to-right shunt.
A
- An example of a left-to-right shunt congenital heart lesion would be an atrial septal
defect (ASD).
7
Q
- When does a right-to-left shunt occur? What is the physiologic effect of this?
A
- A right-to-left shunt occurs when a portion of the systemic venous return is
redirected to the systemic arterial outflow without first circulating through the lung.
Physiologically this would result in desaturated blood returning to the systemic
circulation, and potentially arterial hypoxemia. The degree of hypoxemia would be
dictated by the magnitude of the shunt.
8
Q
- Give an example of a congenital heart defect that results in a right-to-left shunt
A
- An example of a right-to-left shunt congenital heart lesion would be tetralogy
of Fallot.
9
Q
- What are mixing lesions in congenital heart disease? How do mixing lesions affect
the systemic arterial oxygen saturation?
A
- Mixing lesions in congenital heart disease describes a complete blending of the
pulmonary and systemic circulations such that there is identical or nearly identical
oxygen saturations in both circulatory systems. In mixing lesions the systemic
arterial oxygen saturation decreases.
10
Q
- What determines the Qp:Qs ratio in mixing lesions?
A
- In mixing lesions, the Qp:Qs ratio is determined by the relative resistance of
blood flow in the pulmonary and systemic circulatory systems. That is, in mixing
lesions, the ratio of blood flow is determined by pulmonary vascular resistance and
systemic vascular resistance
11
Q
- What is the ideal Qp:Qs ratio in mixing lesions? Why?
A
- The ideal Qp:Qs ratio in mixing lesions is 1. Any preferential flow toward the
systemic circulation would be at the expense of greater desaturation and therefore
less oxygen delivery. Conversely, any preferential flow toward the pulmonary
circulation would be at the expense of cardiac output, and therefore less oxygen
delivery to the tissues. (
12
Q
- What are some factors that can increase systemic vascular resistance?
A
- Factors that can increase systemic vascular resistance are light anesthesia,
systemic nervous system activation, administration of a agonists, and physical
manipulations such as flexing the hips of infants and small children.
13
Q
- What are some factors that can decrease systemic vascular resistance?
A
- Factors that can decrease systemic vascular resistance are deep anesthesia and
the administration of vasodilating drugs, such as nitrates and inhaled anesthetics.
14
Q
- What are five factors that increase pulmonary vascular resistance
A
- Five factors that increase pulmonary vascular resistance are alveolar hypoxemia,
hypercapnia, acidosis, light anesthesia, and hypothermia. Other factors include high
lung volumes and pressures, or low lung volumes with atelectasis.
15
Q
- What are five factors that decrease pulmonary vascular resistance?
A
- Five factors that decrease pulmonary vascular resistance are hyperventilation with
resultant hypocarbia, alkalosis, oxygenation, pulmonary vasodilators such as
inhaled nitric oxide, warmth, and bronchodilators such as albuterol.
16
Q
- What is Eisenmenger syndrome?
A
- Eisenmenger syndrome is a condition that can develop when pulmonary blood
flow is increased over a long period of time, and the direction of the shunt flow
becomes irreversibly left-to-right. This syndrome occurs due to a remodeling of
pulmonary vasculature, an increase in pulmonary vascular resistance, and
ultimately pulmonary hypertension yielding a pulmonary systolic blood pressure
that is higher than systemic systolic blood pressure.
17
Q
- What are some ways an anesthesiologist can prepare for a patient requiring surgery
for congenital heart disease?
A
- An anesthesiologist should prepare by understanding the physiology of the
congenital heart lesion and the subsequent effects of the planned surgery.
Aspects of the patient’s condition that can be improved prior to surgery should
be identified. (
18
Q
- What preexisting conditions might be important to the care of patients with
congenital heart disease?
A
- Preexisting conditions that might be important to the care of patients with
congenital heart disease include a history of prematurity, trisomy 21, DiGeorge
syndrome, and chronic illness such as renal dysfunction, pulmonary edema, and
electrolyte abnormalities. In addition, the preoperative evaluation of morning
admission patients scheduled for congenital heart surgery should include the usual
preoperative evaluation of pediatric patients, such as evaluation for new upper
respiratory tract infections.
19
Q
- What information might be gained from preoperative echocardiograms or magnetic
resonance imaging (MRI)?
A
- Important preoperative information that could be derived from the magnetic
resonance imaging (MRI) and echocardiograms would be anatomic manifestations
of disease, such as an existing ventricular septal defect and concomitant right
ventricular hypertrophy. (
20
Q
- What is a risk factor from a previous sternotomy?
A
- Risk factors from previous sternotomy include increased operative blood loss and
cardiac trauma during dissection secondary to adhesions that may have formed
adherent to the sternum and chest wall.
21
Q
- What are the fasting recommendations for infants and children scheduled for
congenital heart surgery?
A
- Fasting recommendations for infants and children scheduled for congenital heart
surgery should follow the standard American Society of Anesthesiologist
guidelines. (
22
Q
- What is the most important feature of the intravenous administration set up for the
patient scheduled for congenital heart surgery?
A
- The most important feature of intravenous administration set up for patients
scheduled for congenital heart surgery is to meticulously de-air the system.
The inadvertent introduction of an air bubble into the patient’s vascular system
via the intravenous tubing can result in an air embolus entering the systemic
circulation in a patient with a left-to-right shunt. Although the risk is greater in
patients with right-to-left shunts, patients with left-to-right shunts may have
reversal of their shunt during certain phases of the cardiac cycle, during
cardiopulmonary interventions as during manual manipulation of the heart during
surgery, or with coughing in the awake patient.
23
Q
- What are some common side effects of the induction of anesthesia using inhaled
agents, such as sevoflurane or halothane?
A
- Some common side effects of induction of anesthesia with inhaled agents, such
as sevoflurane or halothane, include myocardial depression, decreased heart
rate and myocardial contractility, and decreased systemic vascular resistance.
A halothane induction may also have associated myocardial dysrhythmia and
ventricular irritability
24
Q
- What are some side effects of an intravenous induction of anesthesia using opioids
such as fentanyl?
A
- Some side effects of an intravenous induction of anesthesia using opioids
such as fentanyl would include bradycardia and loss of sympathetic tone.
25
Q
- What are some side effects of an intravenous induction of anesthesia using
ketamine, a drug that preserves sympathetic nervous system tone?
A
- Some side effects of an intravenous induction of anesthesia using ketamine might
include increases in heart rate and myocardial depression
26
Q
- What are some general principles for the induction of anesthesia that might apply to
all patients with congenital heart disease?
A
- Some general principles for the induction of anesthesia that might apply to all
patients with congenital heart disease would include the avoidance of dehydration,
maintaining the patient in sinus rhythm, avoiding myocardial depression, and
avoiding air entrapment in the intravenous and pressure tubings.
27
Q
- What are the goals for the anesthetic management in patients with a left-to-right
shunt?
A
- The goals for the anesthetic management in patients with a left-to-right shunt
are aimed toward the avoidance of hemodynamic changes, such as an increase
in systemic vascular resistance that will increase the magnitude of the shunt.
Decreases in the magnitude of the shunt can be achieved through decreases in
the arterial pressure and increases in the pulmonary vascular resistance, as with
positive-pressure ventilation.
28
Q
- What are the goals for the anesthetic management in patients with a right-to-left shunt?
A
- The goals for the anesthetic management in patients with a right-to-left shunt are
aimed toward the avoidance of worsening arterial hypoxemia by increasing the
magnitude of the shunt. Decreases in systemic vascular resistance and increases
in pulmonary vascular resistance should be avoided.
29
Q
- What are some considerations for the ventilatory management in patients with
congenital heart disease?
A
- Ventilatory management of the patient with congenital heart disease depends on
how the circulatory system will be affected by changes in the pulmonary vascular
resistance relative to the systemic vascular resistance. The goal is to minimize
the impact on blood flow across shunts, and the cardiac lesion must be understood
to best manage the patient. Adjustments in the fractional inspired oxygen
concentration, minute ventilation, peak inspiratory pressure, and the possible use of
the positive end-expiratory pressure are all considerations.
30
Q
- For lesions with excessive pulmonary blood flow such as ventricular septal defects
or atrioventricular septal defects, how should the pulmonary vascular resistance be
managed prior to cardiopulmonary bypass?
A
- For lesions with excessive pulmonary blood flow, such as ventricular septal defects
or atrioventricular septal defects, one should avoid decreases in the pulmonary
vascular resistance prior to cardiopulmonary bypass.
31
Q
- For critically ill patients such as those with truncus arteriosus, what is an important
feature of ventilator management prior to cardiopulmonary bypass?
A
- For critically ill patients such as those with truncus arteriosus, an important feature
of ventilator management prior to cardiopulmonary bypass is to closely
manage the ratio of systemic to pulmonary vascular resistance.
32
Q
- For the Norwood procedure for hypoplastic left heart syndrome, what is an
important aspect of anesthetic management prior to cardiopulmonary bypass?
A
- During the Norwood procedure (stage I for hypoplastic left heart syndrome), an
important aspect of anesthetic management prior to cardiopulmonary bypass is to
maintain the infusion of prostaglandins, maintain nearly equal systemic and
pulmonary blood flow, and protect against myocardial depression and air
embolism.
33
Q
- During the Glenn procedure, what is an important aspect of anesthetic
management?
A
- During the Glenn procedure (stage II procedure for hypoplastic left heart syndrome),
an important aspect of anesthetic management is to maintain a high hematocrit
and recognize that positive-pressure ventilation might decrease pulmonary
blood flow and cardiac outpu
34
Q
- What are poor prognostic factors of a successful Fontan procedure?
A
- Poor prognostic factors of a successful Fontan procedure (stage III procedure
for hypoplastic left heart syndrome) include high pulmonary vascular
resistance, tricuspid regurgitation, and decreased ventricular function.
35
Q
- What are some common congenital lesions that result in inadequate pulmonary
blood flow? What would be an important aspect of ventilatory management of
patients with these lesions?
A
- Common congenital lesions that result in inadequate pulmonary blood flow include
transposition of the great arteries, tetralogy of Fallot, tricuspid or pulmonary atresia,
and total anomalous venous return. An important aspect of the ventilatory
management of patients with these lesions would be to decrease pulmonary
vascular resistance.
36
Q
- Where is the appropriate placement of an arterial line during surgery for coarctation
of the aorta?
A
- The appropriate placement of an arterial line during surgery for coarctation of the
aorta is in the right arm.
37
Q
- During induction of anesthesia for patients with obstructive lesions such as aortic
stenosis, what is the most important to avoid?
A
- During induction of anesthesia for patients with obstructive lesions such as aortic
stenosis, it is most important to avoid tachycardia
38
Q
- What are some common abnormalities seen in patients with Williams syndrome?
A
- Some common abnormalities seen in patients with William syndrome are
supravalvar aortic stenosis, pulmonary arterial stenosis, and coronary artery
abnormalities. (
39
Q
- How should the size of the endotracheal tube be selected?
A
- The endotracheal tube size should be selected according to the age and size of the
patient.
40
Q
- What are some monitors that might be required for children undergoing surgery for
congenital heart disease?
A
- Some monitors that might be required for children undergoing surgery for
congenital heart disease would include arterial pressure monitoring and
transesophageal echocardiography. Monitors are selected on a case-by-case
basis and what is standard for the institutional practice. (
41
Q
- What are some general requirements for the selection of blood products for infants
requiring cardiac surgery?
A
- Some general requirements for the selection of blood products for infants
requiring cardiac surgery are that the blood should be the freshest when possible,
that is less than 5 days of storage. Older blood can become significantly hypokalemic
and result in leftward shifting of the oxygen-hemoglobin dissociation curve
42
Q
- What are some antifibrinolytic drugs used in congenital heart surgery?
A
- Examples of commonly used antifibrinolytic drugs used in congenital heart surgery
are aminocaproic acid and tranexamic acid.
43
Q
- How is anesthesia maintained prior to cardiopulmonary bypass?
A
- Prior to cardiopulmonary bypass, maintenance of anesthesia is usually achieved with a combination of intravenous agents and volatile anesthetics to avoid myocardial depression.
44
Q
- What patients may be able to have early extubation of the trachea?
A
- Early extubation of the trachea may be performed in patients with simple defects, good cardiac reserve, and those undergoing the Glenn or Fontan procedure.
45
Q
- What is a useful way to monitor the cardiac output and circulatory system?
A
- A useful way to monitor the cardiac output and circulatory system is to conduct early and repeated arterial blood gas measurements to allow for appropriate ventilator and acid-base management.
46
Q
- How is anticoagulation for cardiopulmonary bypass achieved?
A
- Anticoagulation for cardiopulmonary bypass is achieved using unfractionated
heparin (3 to 4 mg/kg).
47
Q
- What is the target activated clotting time (ACT) value?
A
- The target activated clotting time (ACT) value is over 400 but the level required
varies in individual practices.
48
Q
- How are flow rates adjusted during cardiopulmonary bypass for infants and children?
A
- Flow rates are adjusted during cardiopulmonary bypass to maintain an age
appropriate mean arterial blood pressure. Parameters used to calculate the flow rate
needed to maintain metabolic function are the patient’s size and estimated blood
volume.
49
Q
- How does the perfusionist control oxygenation and ventilation during
cardiopulmonary bypass?
A
- The perfusionist controls oxygenation and ventilation during cardiopulmonary
bypass by adjusting the blend of air and oxygen (FIO2) and the flow rate (sweep) of
the fresh gas.
50
Q
- How is blood temperature adjusted during cardiopulmonary byp
A
- Blood temperature is adjusted during cardiopulmonary bypass by running cooled or
warmed water through a coil in contact with the blood path
51
Q
- How is mechanical quiescence and myocardial protection provided during
cardiopulmonary bypass?
A
- Mechanical quiescence and myocardial protection is provided during
cardiopulmonary bypass through the administration of cold hyperkalemic
crystalloid solution.
52
Q
- What is the lowest acceptable level of anemia during cardiopulmonary bypass?
A
- The lowest acceptable level of anemia during cardiopulmonary bypass varies from
institution to institution, but is commonly in the range of 20% to 30%
53
Q
- What measures are used to provide cerebral and myocardial protection during
cardiopulmonary bypass?
A
- During cardiopulmonary bypass, cerebral and myocardial protection is achieved by mild to moderate systemic hypothermia. Active rewarming is usually initiated
toward the end of cardiopulmonary bypass
54
Q
- Which surgical repairs require the use of deep hypothermic circulatory arrest?
A
- Surgical repairs of the aorta and aortic arch require deep hypothermic circulatory arrest.
55
Q
- What are some potential negative effects of persistent hypothermia after
cardiopulmonary bypass?
A
- Potential negative effects of persistent hypothermia after cardiopulmonary bypass
include myocardial ischemia, cardiac dysrhythmias, elevated pulmonary vascular resistance, coagulopathies, and renal dysfunction
56
Q
- How can relative bradycardia and atrioventricular node conduction failure during
separation from cardiopulmonary bypass be treated?
A
- Relative bradycardia or atrioventricular node conduction failure that occurs during
separation from cardiopulmonary bypass can be treated by temporary cardiac pacing.
57
Q
- How are patients with long-standing excessive pulmonary blood flow treated on
separation from bypass?
A
- Patients with long standing excessive pulmonary blood flow may have underlying pulmonary hypertension, and may benefit from maneuvers that minimize
pulmonary vascular resistance during separation from bypass.
58
Q
- What is the best approach to the management of a patient who has had a palliative
procedure and is left with a mixing lesion? What is an effective monitoring tool in
these patients?
A
- When a patient has had a palliative procedure and is left with a mixing lesion, the best approach to management is to balance the circulatory system so that the
pulmonary vascular resistance and systemic vascular resistance yield a balanced circulation. An effective monitoring tool in these patients is the pulse oximeter.
A balanced circulatory system in these patients will result in a systemic oxygen saturation of 80%. Excessive pulmonary blood flow exists when
systemic oxygen saturation is greater than 85% to 90%, whereas when the systemic
oxygen saturation is lower than 70% there may be inadequate pulmonary
blood flow.
59
Q
- What are some common vasoactive drugs used during separation from
cardiopulmonary bypass?
A
- Some common vasoactive drugs used during separation from cardiopulmonary bypass in congenital heart surgery are dopamine, epinephrine, norepinephrine, and milrinone
60
Q
- What are some causes of difficulty in separation from cardiopulmonary bypass in
congenital heart surgery?
A
- Some causes of difficulty in separation from cardiopulmonary bypass in congenital heart surgery include inadequate pulmonary blood flow (arterial hypoxemia), inadequate systemic blood flow (hypotension and metabolic acidosis), valvular
dysfunction, decreases in cardiac output, decreased systemic vascular resistance, cardiac rhythm disturbances, and hypovolemia
61
Q
- What rescue measure can be used if a patient cannot be weaned from
cardiopulmonary bypass?
A
- A rescue measure that can be used if a patient cannot be weaned from cardiopulmonary bypass is extracorporeal life support. (428
62
Q
- What are important complications of protamine administration?
A
- Important complications of protamine administration include anaphylactic, anaphylactoid, hypotensive, or severe pulmonary hypertensive reactions. (428)
63
Q
- What are contributors to postoperative coagulopathy in congenital heart surgery?
A
- Contributors to postoperative coagulopathy in congenital heart surgery include coagulation factor deficiencies, hypothermia, and hypocalcemia. (428)
64
Q
- What is the best method to replace blood components in infants?
A
- The best method to replace blood components in infants is noting their small intravascular volume, and administering products carefully in aliquots. (428)
65
Q
- What is a common side effect of the administration of citrated blood products?
A
- A common side effect of the administration of citrated blood products is hypocalcemia. (429)
66
Q
- What agents can be used for refractory bleeding after cardiopulmonary bypass?
A
- Refractory bleeding after cardiopulmonary bypass can be treated with recombinant factor VIIa when conventional hemostatic therapy has failed to stop the bleeding. (429)
67
Q
- What are common parameters to be actively managed after pediatric cardiac surgery in the intensive care unit?
A
- Common parameters that are actively managed after pediatric cardiac surgery in the intensive care unit involve the correction of various electrolyte, glucose, and ventilatory, circulatory, and hematologic parameters.
