Cyanotic Congenital Cardiac Defects: Diagnosis & Therapy by Tom Kulik, MD, for OPENPediatrics

Aug 18, 2023

Cyanotic Congenital Cardiac Defects: Diagnosis & Therapy by Tom Kulik, MD, for OPENPediatrics

Listen to Dr. Thomas Kulik review the physiological causes of cyanosis in the newborn, explain the pathophysiolgoy of some of the most common cyanotic congenital cardiac defects, review diagnostic considerations for these conditions, and describe some therapeutic management strategies.

Initial publication: March 8, 2016.
Last reviewed: May 13, 2019

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Content

23.38 -> Cyanotic Congenital Cardiac Defects: Diagnosis and Therapy, by Doctor Tom Kulik.

29.929 -> I'm doctor Tom Kulik. I'm a pediatric cardiologist and cardiac intensivist at the Children's

36.75 -> Hospital, Boston. This lecture will be the second part of two lectures in regards to

45.14 -> the diagnosis and management of the infant with cyanosis.

50.32 -> Introduction.

51.8 -> To briefly preview the lecture, we will first review the physiology of cyanosis that was

56.769 -> covered in the first of these two lectures. We will discuss general diagnostic considerations.

65.21 -> We will briefly go over some of the most important types of cyanotic heart disease, especially

71.189 -> the types that are present in the neonate. And we will discuss ICU based therapy. And

78.329 -> by that we're not going to talk about surgical palliation, or surgical correction of these

83.49 -> lesions, but rather focus on the sort of things that the neonatologist and intensivist will

89.619 -> be involved with in their unit-- stabilizing and preparing the baby for more definitive

96.469 -> treatment.

97.859 -> Physiology. Let's briefly talk about the physiology of cyanosis caused by congenital heart defects

106.649 -> and review material that we had previously discussed. There are basically four types

113.149 -> of physiological reasons why babies are cyanotic. They can have right to left intraventricular

119.31 -> shunt, as illustrated here by a baby with Tetralogy of Fallot. In this case, there was

125.13 -> a ventricular septal defect and outflow obstruction between the right ventricle and pulmonary

131.19 -> artery. Hence, blood tends to go right to left across the VSD into the aorta.

137.84 -> Right to left, interatrial shunting. In this case, it's a baby that has severe pulmonary

143.34 -> stenosis. The obstruction to blood flow from the right ventricle to the pulmonary artery

148.26 -> is so severe that an entire cardiac output cannot be injected into the lungs, and hence,

154.08 -> there's a considerable amount of right to left shunting at the atrial level, not ventricular

158.85 -> level. Let's talk about what I might term simple, or perhaps more commonly termed, complete

164.74 -> mixing. And what you see here is an example of a baby that has a particular type of single

171.45 -> ventricle lesion called tricuspid atresia. In this case, there is what I might term simple

178.39 -> or complete mixing of blue system venous blood with red pulmonary venous blood. And as a

185.41 -> result, there is a cyanosis.

187.55 -> And finally, transposition physiology is the physiology that occurs in babies that have

194.97 -> a D-transposition of the great vessels. That is to say the aorta is attached to the right

200.33 -> ventricle and the pulmonary artery to the left ventricle. In which case, there tend

204.42 -> to be two separate circuits whereby the blue blood coming back from the body to the heart

210.59 -> is ejected right back out to the body again, and red blood from the lungs is re-ejected

218.6 -> to the lungs. These patients can only survive ex-utero by virtue of some degree of mixing

225.6 -> of the red and blue streams. And we will discuss this a little bit more in just a few minutes.

231.91 -> There are multiple determinants of arterial oxygen saturation in congenital heart disease.

239.84 -> They can pretty much be boiled down to these five factors. The first is pulmonary venous

246.59 -> oxygen saturation. Obviously, a baby with congenital heart lesion will be bluer than

252.24 -> he or she would otherwise be if there is lung disease, and hence, the pulmonary venous blood

257.35 -> is not fully saturated. The ratio of pulmonary to systemic blood flow, also known as Qp:Qs,

265.419 -> is very important in babies with either complete mixing lesions, or even a simple right to

272.729 -> left shunting. The amount of systemic blood flow, the hemoglobin content of the blood,

280.35 -> and the total body O2 consumption are also important in determining arterial oxygen saturation.

287.18 -> And the reason for this is that whenever there is right to left shunting, the blue blood

293.59 -> returning from the body tends to, essentially, dilute out the oxygen level of the red blood

300.04 -> returning from the lungs. The bluer the blue blood is, the less red the arterial blood

308.23 -> will be as it's ejected from the heart. So as systemic blood flow falls, mixed venous

314.54 -> oxygen saturations also tend to fall. With less O2 delivery to the body because of lower

321.47 -> hemoglobin, the mixed venous O2 saturation tends to fall. And as more oxygen is extracted

328.91 -> because of high oxygen consumption, that also tends to negatively impact the oxygen saturation

335.03 -> of the venous blood.

337.27 -> So these are the key determinants of arterial O2 saturation in just about any congenital

344.71 -> heart lesion. Perhaps the only exception to that is D-transposition of the great arteries.

350.84 -> And there, the key issue is how much mixing of the red blood and the blue blood streams

356.54 -> occurs. And again, we'll talk about this a bit more in a few minutes.

364.15 -> Diagnostic Considerations.

365.15 -> Let's move on to general diagnostic considerations. We're going to focus primarily on the clinical

374.78 -> characteristics which help discriminate congenital heart disease from lung disease and persistent

383.639 -> pulmonary hypertension of the newborn. We're not going to try to provide enough information

389.73 -> to allow one to make a specific diagnosis of a heart defect without performing an echocardiogram,

398.81 -> because echo is really the definitive way we make these diagnoses in the vast majority

404.41 -> of cases. So I'm going to emphasize for the next few minutes the things that one can observe

411.61 -> in a baby in terms of physical signs and symptoms that make one most concerned about the possibility

418.8 -> of a congenital defect, and hence initiating prompt detailed evaluation of such.

427.18 -> So let's talk about these red flags for congenital heart disease. The first is babies that are

434.52 -> cyanosis with what one of the kind of founding fathers of pediatric cardiology, Alex Nadas,

441.979 -> termed "happy tachypnea." Happy tachypnea is tachypnea without dyspnea, or a baby who's

449.11 -> breathing fast but very easily. Babies with lung disease of course tend to have dyspnea

455.71 -> because their lungs are relatively non-compliant. On the other hand, babies with congenital

461.79 -> heart disease tend to have very compliant lungs, and hence, although they will be tachypnic

468 -> because of a hypoxic respiratory drive, they don't tend to breathe particularly hard.

473.199 -> And so happy tachypnea tends to make one think more of heart disease and less of lung disease.

479.44 -> Now, one has to be careful though. There is a particular type of heart lesion, total anomalous

486.46 -> pulmonary venous connection, that is to say, when all the pulmonary veins returning from

491.54 -> the lungs have obstruction somewhere between their origin and the heart, these babies can

501.09 -> develop very severe pulmonary edema as is illustrated on this chest x-ray of a young

507.919 -> patient with total obstructed veins. And these babies will have a considerable amount of

514 -> dyspnea. So one always has to keep obstructive total veins in mind when presented with the

519.919 -> cyanotic baby that has a lung finding suggestive of pulmonary edema.

528.529 -> The second red flag for congenital heart disease is differential cyanosis. Differential cyanosis

534.639 -> is when the oxygen saturations are different in the right arm versus the lower body. And

540.93 -> there are basically two types of differential cyanosis. The first is differential cyanosis

550.11 -> due to right to left shunting of systemic venous blood into the descending aorta. This

558.98 -> can occur under two circumstances.

561.33 -> One is persistent pulmonary hypertension of the newborn. Babies that have this particular

569.36 -> disease have very high pulmonary resistance. And if they have an open ductus, especially

574.01 -> a large open ductus, they may actually shunt blood from the pulmonary artery into the descending

580.5 -> aorta, such that their oxygen saturations in their right arm will be considerably higher

586.92 -> than in their legs. Not all babies with PPHN have differential cyanosis, but certainly

595.87 -> many of them do.

600.08 -> Those same findings however, can occur in babies with congenital heart lesions. For

604.56 -> example, I've shown a baby with interruption of the aortic arch. In this particular set

612.12 -> of circumstances, all of the profusion to the lower body is via the right ventricle

617.27 -> across the ductus And so these kids will tend to have substantially lower oxygen saturation

623.69 -> in the lower extremities than in the right arm. So differential cyanosis, while it can

630.49 -> occur without a congenital heart lesion, specifically with PPHN, can also occur with certain forms

637.45 -> of heart disease.

639.91 -> The second flavor, if you will, of differential cyanosis is reverse differential cyanosis.

647.32 -> And with reverse differential cyanosis, the oxygen saturations are actually higher in

653.54 -> the lower body than in the right arm. And where this is occasionally seen, and I think

660.02 -> pretty much the only time it's occasionally seen, is in babies with d-transposition of

665.209 -> the great vessels or a very similar anatomic lesion.

670.1 -> In this case, if there is very high resistance to blood flow in the lungs, and there's a

675.88 -> patent ductus arteriosis, when the left ventricle ejects blood into the pulmonary artery, a

682.209 -> certain fraction of it will tend to go across the ductus into the descending aorta. Since

688.19 -> this is red pulmonary venous blood, these patients will actually tend to have higher

693.83 -> oxygen saturation in the legs than in the right arm. This can occur either because,

700.86 -> as I just mentioned, high pulmonary vascular resistance, or sometimes coarctation of the

706.86 -> aorta in a d-transposition, where there is narrowing of the isthmus of the aorta, the

712.75 -> segment between the left subclavian artery and the ductus. And that can also give reverse

722.61 -> differential cyanosis. So the finding of reverse differential cyanosis is very highly suggestive

729.72 -> of congenital heart disease.

734.019 -> Murmurs can constitute a third red flag for congenital heart disease. As I think most

741.41 -> folks know, very soft murmurs are very common in babies, and grade one to two over six murmurs

748.75 -> do not necessarily connote congenital heart disease. On the other hand, murmurs of grade

754.41 -> three intensity or louder are quite unusual in otherwise normal babies, and certainly

761.25 -> raise a red flag in a baby who has lower than normal arterial oxygen saturations. Continuous

769.519 -> murmurs in the back are also very uncommon in otherwise normal newborns and make one

774.55 -> think of a lesion like Tetrology of Fallot with pulmonary atresia.

779.959 -> And there is one murmur in particular, that is to say, the to and fro, not so much continuous,

786.019 -> but to and fro murmur at the left upper sternal border, which is almost pathogenomic of babies

792.98 -> that have absent pulmonary valve syndrome, also known as Tetrology of Fallot absent pulmonary

797.87 -> valve. There are very few other situations in which a typical to and fro murmur like

803.519 -> this is heard. So murmurs can sometimes put one on the alert for congenital heart lesion.

810.79 -> Point number four refers to the so-called hyperoxia test, that is to say if one gives

818.24 -> a baby with lung disease a very high inspired oxygen, generally the PO2 will go up substantially

825.47 -> or the O2 sat goes up substantially by virtue of the fact that most babies that are cyanotic

832.38 -> by virtue of lung disease have VQ mismatch as a primary cause for this. And this is quite

839.74 -> responsive to oxygen. One can read various cut-off levels for arterial PO2 in response

847.779 -> to 100% oxygen as discriminating between congenital heart disease and lung lesions. I've used

855.97 -> PO2 of 200, because it's certainly possible for babies with cyanotic mixing lesions to

863.829 -> have PO2s of greater than 150 on 100% oxygen. But to be quite honest this test doesn't have

870.82 -> a clear cut cut off.

874.079 -> Babies with very severe lung disease may not increase their arterial PO2s that much on

880.73 -> 100% oxygen. On the other hand, babies with certain forms of heart disease, for example,

886.47 -> total anomolous pulmonary venous connection below the diaphragm will occasionally have

892.279 -> streaming pulmonary venous blood in such a way that the arterial PO2 can actually be

896.95 -> greater than 200 in the upper body. And so, it's very hard to give a discrete reliable

908.99 -> cut off for the hyperoxia test. I think it would be safe to say that any PO2s less than

920.19 -> 200 or even somewhat greater than that, would make one have to consider the possibility

926.82 -> of congenital heart defects.

928.31 -> And in fact, probably a more sophisticated way to think about this, although a non-quantitative

935.279 -> way, is to consider that whenever the arterial PO2 is out of proportion to the chest x-ray,

942.579 -> one is concerned about congenital heart defects, in particular relatively low PO2s, despite

949.589 -> a normal chest x-ray. Again, one has to be cautious. Babies with obstructed total anomalous

958.139 -> pulmonary venous connection can have very wet appearing chest x-ray, which might imply

962.98 -> pneumonia, but in fact, is pulmonary edema due to their congenital heart lesion.

968.3 -> Electrocardiogram is generally normal in most babies with cyanotic heart disease, and isn't

975.07 -> terribly useful in most cases. Therefore, although the presence of left axis deviation,

980.62 -> that is to say, QRS axis of less than a zero does run along with certain forms of heart

988.06 -> disease, cyanotic heart disease especially. Tricuspid atresia certainly raises a red flag

995.11 -> in the circumstances in which left axis deviation occurs.

1000.57 -> Finally the chest x-ray can be helpful. Certainly dextrocardia doesn't prove the presence of

1007.389 -> congenital heart disease although it makes quite likely. Midline stomach bubble, as one

1012.61 -> sees with hetrotaxy syndromes also markedly increases the likelihood of congenital heart

1018.63 -> disease. Right aortic arch can be a finding in a normal person, but it also suggests the

1027.059 -> possibility of Tetralogy of Fallot, truncus arteriosus or transposition views to pulmonary

1033.22 -> stenosis. And a classic finding with babies that have Tetralogy of Fallot or Tetrolagy

1040.47 -> of Fallot with pulmonary atresia is the upturned cardiac apex combined with the flat pulmonary

1046.169 -> arterial segment on the chest x-ray and right aortic arch as we see in this film of a baby

1053.049 -> with Tetralogy of Fallot in pulmonary atresia.

1057.44 -> Types of Cyanotic Congenital Heart Disease.

1061.49 -> So having discussed the sorts of physical findings that make one concerned about heart

1067.57 -> disease, let's talk about the specific types of cyanotic heart disease that occur most

1075.65 -> often in babies with this lesion. We're not going to go over detailed descriptions, but

1080.669 -> I hope to provide enough information that you'll have a general idea of what you will

1085.309 -> be dealing with about 99% of the time when dealing with cyanotic infants.

1090.46 -> And I'd like to break these lesions down into what you might call a ductus-centric classification.

1097.28 -> That is to say, categorize the babies, the patients, in this way-- those that have severe

1103.6 -> obstruction to pulmonary blood flow and, therefore, will require an open ductus and, therefore,

1108.95 -> Prostaglandin E1 for palliation. Number two, babies that have little or no obstruction

1114.74 -> to pulmonary blood flow, in which case PGE-1 may not be either required or even helpful.

1121.88 -> The third type of classification are babies with d-transposition of the great vessels.

1129.7 -> Those babies may benefit from an open ductus, but not always. And finally, babies with a

1136.22 -> total anomalous pulmonary venous connection with obstruction. In those cases, babies neither

1142.36 -> benefit from-- in fact, they actually have a deleterious effect from Prostaglandin E1.

1154.33 -> So let's start with the first classification, babies with severe obstruction to pulmonary

1160.71 -> blood flow, in which case Prostaglandin E1 is required therapy. The first would be babies

1167.53 -> with critical pulmonary stenosis or pulmonary atresia. As I mentioned earlier in this lecture,

1173.58 -> babies with this particular lesion have such a high degree of outflow obstruction between

1179.37 -> the right ventricle and the pulmonary artery, that a full cardiac output cannot be ejected

1184.45 -> across this narrow pulmonary valve into the lungs. And hence, there is a very large amount

1189.34 -> of right-left shunting at atrial level. There's a diagram of that on the left.

1195.08 -> On the right is a lateral view of an angiogram, which is an injection into the right ventricle.

1202.11 -> And what you see here is a good-sized right ventricle, but with relatively heavy trabeculations

1209.89 -> due to hypertrophy that's occurred in utero because of the very high right ventricular

1214.39 -> pressure. And you see a very thickened pulmonary valve.

1217.799 -> Ordinarily, you can't really see the pulmonary valve very well on angiography and with a

1223.99 -> relatively small jet of contrast that goes across it. This is kind of a typical angio

1230.03 -> of a baby with critical valvar pulmonary stenosis. Because of the marked limitation of pulmonary

1236.48 -> blood flow in critical PS, patency of the ductus is critical.

1244.91 -> Tetralogy of Fallot, if severe enough, can present with life-threatening hypoxemia in

1248.41 -> a neonate because of a marked reduction in pulmonary flow. I want to make the strong

1255.24 -> point, however, that most babies with Tetralogy after they're born, do not have severe obstruction

1262.27 -> to right ventricular outflow. Most neonatal Tretralogies have quite adequate oxygen saturations

1271.179 -> without an open ductus, and really require very little in the way of therapy.

1276.59 -> But in the case of a baby with severe obstruction, Prostaglandin E1 may be required. There other

1283.11 -> lesions that are similar to Tetralogy of Fallot. For example, double outlet right ventricle

1287.73 -> with pulmonary stenosis, that have much the same physiology.

1294.049 -> Babies with single ventricle lesions that have a high degree of obstruction to pulmonary

1298.88 -> blood flow also require Prostaglandin E1. This is a diagram of a patient with tricuspid

1305.01 -> atresia. In the case of tri-atresia there is basically no right ventricle, no tricuspid

1310.53 -> valve. And so systemic used blood goes from the 2 cava into the right atrium, crosses

1316.919 -> the atrial septum into the left atrium and mixes with pulmonary venous blood there, enters

1321.97 -> the left ventricle, some is ejected into the aorta. And then some finds its way into the

1328.669 -> lungs, presuming there is an open VSD in a sub-pulmonary chamber.

1334.14 -> If the VSD is quite restrictive, or the area underneath the pulmonary artery is quite narrow,

1340.289 -> there may be a critical reduction in pulmonary blood flow. In which case, Prostaglandin E1

1346.059 -> won't be required. Now, not all tricuspid atresia babies have this critical reduction.

1352.15 -> Some do not require prostaglandins. But some do. And this is true for other single ventricle

1360.62 -> defects that have restricted pulmonary blood flow.

1364.049 -> Finally, this is a rare lesion. Even large centers will see this only a very few times

1371.13 -> of the year. But it's worth mentioning.

1372.66 -> Ebstein's Malformation basically is when the tricuspid valve is displaced into the right

1381.03 -> ventricle such the right ventricular mass is reduced in functional volume. And the valve

1387.59 -> itself is very nonfunctional. So it tends to have marked regurgitation.

1392.52 -> There's a whole spectrum of Ebstein's. Very mild Ebstein's is consistent with an asymptomatic

1398.87 -> long life. Very severe Ebstein's shows up in the way I've illustrated on this screen,

1405.62 -> with a baby that has a massively dilated heart in utero and immediately ex-utero and a right

1413.809 -> ventricle that by virtue of the tricuspid regurgitation, is basically insufficient to

1420.22 -> eject blood out the pulmonary artery and into the lungs. These babies require an open ductus

1427.2 -> in order to provide adequate pulmonary blood flow.

1432.799 -> The second general category of patients with cyanotic heart disease are those that have

1437.72 -> little or no obstruction to pulmonary blood flow and, therefore, do not require Prostaglandin

1442.96 -> E1 for palliation. As I mentioned before, babies with Tetralogy of Fallot rarely need

1449.919 -> a ductus. Most do not have severe right ventricular outflow obstruction. And so this would generally

1456.12 -> be the case for most babies with Tetralogy.

1459.46 -> Babies with Tetralogy of Fallot and so-called MAPCAs, or Multiple Aortopulmonary Arteries,

1469.46 -> are patients that also oftentimes do not require prostaglandin for palliation. Babies with

1476.35 -> this particular lesion are like Tetralogy in the sense that there are two normal-sized

1481.57 -> ventricles and a ventricular septum defect. The aorta generally comes off mostly the left

1488.61 -> ventricle. But instead of having some connection between right ventricle and the pulmonary

1493.23 -> arteries, there is no connection. And blood finds its way into the lungs either as through

1499.289 -> the so-called aortopulmonary collateral vessels or, in some cases, through an ductus arteriosus.

1507.84 -> Babies that do not have a ductus arteriosus and has supply through the aortopulmonary

1513.35 -> collateral vessels, of course, are not ductile dependent. I've illustrated the angiogram

1518.72 -> on the right side of the slide as arrows pointing to these collaterals that come directly of

1525.25 -> the aorta. These babies are not prostaglandin dependent. Do hasten, however, to make note

1532.679 -> of the fact that some subset of babies with Tetralogy of Fallot and pulmonary atresia

1538.75 -> will basically have their entire pulmonary blood flow supplied via a ductus. And babies

1544.95 -> with that lesion do require an open ductus, and hence, generally Prostaglandin E1 palliation.

1552.48 -> Babies with truncus arteriosus do not require Prostaglandin E1 unless there is some additional

1558.23 -> lesion such as interruption of the aortic arch. Babies with truncus basically have two

1564.059 -> normal-sized ventricles and a VSD. And then there's a single large vessel that arises

1570.4 -> from these two ventricles this gives rise to both the aorta and pulmonary arteries.

1575.83 -> And this is not a ductile-dependent form of cyanotic heart disease. Babies with single

1583.309 -> ventricle lesions that have no obstruction to pulmonary blood flow do not require Prostaglandin

1590.4 -> E1 in order to maintain adequate pulmonary blood flow.

1593.75 -> Now I hasten to make note of the fact that some of these babies can have obstruction

1599.07 -> to their aorta, either flow from the ventricle into the aorta or coarctation or other narrowing

1606.429 -> of the aorta. In that case, Prostaglandin E1 may be required. But simply talking about

1612.7 -> babies with cyanotic defects, if there is no obstruction to pulmonary blood flow in

1621.27 -> a single ventricle patient, there is no need for a Prostaglandin E1 in order to maintain

1627.24 -> adequate pulmonary blood flow.

1628.99 -> In the case of babies with transposition of the great arteries, Prostaglandin E1 may be

1636.559 -> helpful. As you recall, these babies require mixing of the red and blue blood streams in

1643.289 -> order to provide adequate 02 delivery to the body. This generally has to, at least in part,

1649.97 -> occur at the level of the atrial septum. Mixing at the level of the ductus as a sole level

1656.69 -> of mixing is not adequate.

1658.82 -> But the presence of an open ductus can increase pulmonary blood flow and augment mixing of

1665.34 -> the atrial level. And so for that, using Prostaglandin E1 may be helpful in babies with transposition.

1672.37 -> Not all babies will adequately respond to this, however.

1678.679 -> There is an occasional baby with d-Transposition that actually becomes acutely ill after introduction

1685.659 -> of this medication for whatever reason. So one has to keep this in mind. But by and large,

1694.32 -> maintaining ductile patency is helpful in these patients with transposition.

1700.15 -> Babies with total anomalous pulmonary venous connection, on the other hand, may actually

1703.86 -> be harmed by Prostaglandin E1. If these babies have obstruction to pulmonary venous return

1710.73 -> to the heart, the resistance to blood flow through the lungs is very high. In which case,

1716.89 -> if the ductus arteriosus is open, blood that's ejected from the right ventricle tends to

1722.72 -> go across the ductus into the descending aorta. And hence, total pulmonary blood flow is reduced.

1728.44 -> So with total anomalous pulmonary venous connection, one generally avoids the use of Prostaglandin

1735.18 -> E1.

1740.86 -> ICU Therapy.

1743.61 -> So finally, what is this ICU based therapy that's available for patients that are hypoxemic?

1750.65 -> Well, basically there are three things that one needs to do in order to effectively apply

1755.99 -> this therapy. The first thing is to assess and secure adequate O2 delivery for the patient.

1764 -> Even before one has a definitive diagnosis, it's necessary to attend to this. It's important

1770.65 -> when assessing the baby from life-threatening hypoxemia. And by the way to measure arterial

1776.11 -> oxygen saturations or PO2s. Transcutanious oximeters are really not very accurate when

1784.169 -> the oxygen saturation is low and really aren't acceptable in many cases for determining whether

1794.59 -> a baby is seriously hypoxemic or merely has a lower than normal oxygen level.

1800.21 -> It's necessary to make ultimately an accurate diagnosis and then eventually definitive therapy

1807.07 -> is applied, which is oftentimes surgical. But there is a considerable amount of opportunity

1813.22 -> to make these patients better, even without surgery.

1817.09 -> So what is life-threatening hypoxemia? At least as far as I'm aware, there is no absolute

1822.74 -> arterial PO2 that qualifies for this.

1827.33 -> And so it's very important to think not only in terms of arterial saturation, but O2 delivery

1832.77 -> to the tissues.

1834.409 -> O2 delivery-- the equation describes oxygen delivery to the tissues-- is very simple.

1842.059 -> It's basically delivery equals content of arterial content of oxygen, which is related

1849.51 -> to both the pulmonary venous, oxygen saturation, as well as hemoglobin, and the systemic blood

1855.99 -> flow which is in a normal person-- in a normal heart-- a cardiac output.

1861.97 -> One uses serum lactate since, to some extent, serum bicarb levels are indicators of tissue

1869.58 -> dysoxia. I don't think we know for sure that a non-elevated lactate level necessarily implies

1879.09 -> that all organs, especially the brain, have adequate O2 delivery. But as a general index

1886.669 -> of total O2 delivery sufficiency, a lack of high lactates tends to be a somewhat reassuring.

1895.08 -> In general, I think one could say that with acceptable hemoglobin and cardiac output,

1903.289 -> at least in newborn babies, arterial PO2s in the low 20 range are tolerated at least

1911.2 -> for some period of time. And certainly, arterial PO2s of greater than 25 seem to be well tolerated

1918.82 -> for at least some period of hours or perhaps even longer.

1922.86 -> But again, I emphasize that it's critical that hematocrit be appropriate as well as

1929.1 -> cardiac output. If these determinants of O2 delivery are reduced, then that means that

1934.809 -> even with a marginally acceptable arterial PO2, O2 delivery may not be sufficient.

1941.89 -> So what can you do for a baby that has inadequate arterial delivery and saturations? Well, pretty

1950.25 -> much from regardless of the form of disease-- and this applies to lung disease as well as

1956.35 -> heart disease-- there are a number of things one can do to improve O2 delivery.

1960.97 -> One can optimize hematocrit. I don't think anybody knows precisely what the very most

1966.789 -> optimum adequate is for O2 delivery. But it seems in general that hematocrit somewhere

1972.95 -> in the 45 range are probably pretty close.

1976.69 -> One can do one's best to obtain adequate systemic diffusion, appropriate volume infusion as

1982.7 -> needed, and inotropic agents can be very helpful. Time does not permit a full discussion of

1990.029 -> these, but the general use of these agents to improve cardiac output can be helpful in

1996.429 -> cyanotic patients.

1998.22 -> When we optimize a ventilation which oftentimes will require means of mechanical ventilation,

2004.01 -> but not always, and can minimize total body O2 consumption through the use of chemical

2010.82 -> paralysis, mechanical ventilation, sedation, and temperature control.

2014.929 -> And finally, one can use therapy to reduce or eliminate acidosis, make sure glucose and

2024.33 -> calcium levels are acceptable.

2026.86 -> Prostaglandin E1 is a definitive palliation, although not permanent therapy for many lesions.

2037.6 -> It's certainly necessary when there's high grade anatomic obstruction, pulmonary blood

2042.48 -> flow.

2042.83 -> As I noted, it's often, but not always helpful in the transposition. And as also noted, it

2048.95 -> can actually be harmful with obstructed total anomalous pulmonary venous connection.

2054.179 -> Or in any case in which a systemic hypotension may be non-helpful.

2061.02 -> It's important to note that Prostoglandin E1 is a systemic vasodilator. And when this

2066.19 -> medication is started, it's oftentimes necessary to use some degree of volume infusion, or

2072.059 -> even inotropic and alpha-adrenergic agents in order to secure adequate blood pressure.

2080.399 -> One also needs to keep in mind that the Prostoglandin E1 also can cause apnea. This is especially

2086.739 -> true in prematures. It also seems to have an added effect along the sedation, so that

2093.069 -> babies that are sedated for procedures or tests or more prone to apnea with Prostoglandin

2098.619 -> E1, and one needs to keep this in mind.

2102.469 -> Babies that are transported shortly after an E1 has been initiated, or even for that

2107.7 -> matter a number of hours after it, because sometimes the apnea that occurs with this

2111.859 -> medication occurs many hours later.

2115.039 -> One needs to consider whether or not this patient should be intubated. Whether or not

2121.029 -> intubation is indicated in this situation depends upon the exact circumstances, but

2125.839 -> one always needs to consider this before transporting a patient.

2131.91 -> The dose that's used to open a closed ductus with E1 is 0.1 micrograms per kilogram per

2138.809 -> minute. For babies that already have opened ductuses, and one wants to maintain patency,

2144.749 -> we use a much lower dose. We generally use between 0.01 and 0.02 micrograms per kilogram

2153.099 -> per minute in order to maintain patency.

2155.7 -> As I noted before, it's important if one wants to avoid apnea to try to be ginger in one's

2162.299 -> use of sedatives in patients on the Prostoglandins.

2166.969 -> There is also at least one paper in the literature that would suggest that pre-treatment with

2173.069 -> aminophylline, and one presumes that caffeine may have the same effect-- it reduces the

2178.539 -> risk of apnea in babies with Prostoglandin E1 substantially.

2186.229 -> Definitive palliation for babies mostly with d-transposition of the great vessels-- there

2191.17 -> are a few other unusual circumstances-- but primarily d-transposition of the great vessels

2197.109 -> is really affected by Rashkind Balloon Septostomy. It's performed by skilled personnel, generally

2204.799 -> well-trained pediatric cardiologists. It can be done at the bedside using echocardiographic

2210.089 -> guidance or in the cath lab.

2212.109 -> There is a relatively low risk of complications with this procedure, but the ones that do

2217.94 -> occur can be very serious. There is a risk of air embolism because of the technical features

2226.65 -> of the way this is generally done. Also, some risk of injury to systemic or pulmonary veins

2232.569 -> or AV valves.

2234.299 -> So it's important that the hands performing this procedure be skilled and experienced.

2239.999 -> Many babies that have this particular procedure, by the way, still require an open ductus for

2246.359 -> adequate oxygen saturations.

2250.029 -> Simply having an open atrial septum does not always ensure adequate mixing.

2255.869 -> This is an angiogram of a baby with d-transposition. It has a Rashkind Balloon Septostomy and catheter

2262.999 -> placed in the left atrium. And the catheter came up the inferior vena cava across the

2268.459 -> foraminal valley. And the balloon was inflated, which by the way, has contrasts, radio-opaque

2277.91 -> contrasts, and it was inflated. And you see the balloon is briefly advanced and then forcibly

2285.64 -> pulled across the atrial septum into the right atrium, as illustrated here.

2297.66 -> Finally, I'll just briefly mention that there are a few unusual situations that you might

2307.16 -> wind up encountering that will require slightly different therapy. There are a few, but not

2314.799 -> many patients with congenital heart lesions that have increased pulmonary vascular resistance,

2320.359 -> much as is seen in persistent pulmonary hypotension of the newborn.

2325.099 -> The only lesion in which this is seen with any frequency-- and even in this case-- it's

2331.279 -> unusual, but not unheard of, is d-transposition of the great vessels.

2335.64 -> These babies occasionally have very high resistance, which to some extent, is oftentimes responsive

2341.539 -> to inhaled nitric oxide or other vasodilators, and tends to resolve after a few days.

2349.089 -> These patients may require nitric oxide or even ECMO support in order to support them

2355.19 -> while their vascular resistance is falling postnatally.

2359.979 -> Babies with congenital heart disease that have persistent findings of significantly

2365.7 -> elevated pulmonary vascular systems are quite uncommon, and make one think of the possibility

2372.19 -> of alveolar capillary dysplasia, which has been described in a number of congenital heart

2378.029 -> patients, especially left-side obstructive lesions.

2383.13 -> Some babies with right-side obstructive lesions, especially a Tetralogy of Fallot, will have

2389.029 -> a congenital absence of the ductus arteriosus.

2392.17 -> If the baby has no ductus and severe outflow tract obstruction, Prostoglandin E1 will not

2400.049 -> be of any use in palliation, of course.

2403.759 -> These patients can be treated sometimes palliated for some period of time by increasing their

2409.779 -> systemic vascular resistance so as to effectively force blood across the high-grade obstruction

2416.41 -> in the right ventricular outflow tract. Phenylephrine is most typically used for this.

2423.89 -> ECMO support can be useful. Sometimes these babies can be treated in the Cath lab by placement

2429.42 -> of a stent out the right ventricular outflow tract in order to open this up sufficiently

2433.609 -> for adequate PO2s.

2437.88 -> Patients with obstruction of the total anomalous pulmonary venous-- anomalously connected pulmonary

2445.63 -> veins require emergency surgery because there's really no effective form of palliation other

2451.269 -> than very short-term ECMO under unusual circumstances.

2455.9 -> So, by and large, these patients require prompt diagnosis and prompt definitive surgical therapy.

2462.589 -> Finally, to finish up the lecture, I'd just like to spend a few minutes talking about

2467.63 -> ICU therapy for patients with single ventricle physiology and unobstructed pulmonary blood

2474.759 -> flow.

2475.509 -> Patients with this combination of defects tend to develop over the first few postnatal

2480.88 -> days. Excessive pulmonary blood flow-- and reason is, of course, this is normally a resistance

2486.39 -> to blood flow through the lungs is much lower than the body. And as pulmonary resistance

2491.789 -> falls-- and it tends to fall quite rapidly after birth-- these patients actually tend

2497.13 -> to send more and more blood to the lungs and less blood to the body.

2501.819 -> Since the heart can only pump out a total amount of blood-- a volume of blood at any

2506.479 -> one time, these patients tend to have only mild hypoxemia, their saturations are in the

2512.66 -> 80s or even 90s. And there is a tendency for systemic bloodflow to be reduced due to the

2519.319 -> excessive bloodflow into the lungs.

2521.66 -> Typical lesions that have this or truncus arteriosus-- generally, in most cases-- do

2526.259 -> not have obstruction of the pulmonary arteries, hypoplastic left heart, or any single ventricle

2533.309 -> defect with unobstructed total pulmonary bloodflow.

2537.209 -> This is a slide that I had shown in the previous part 1 lecture that relates the total amount

2545.259 -> of pulmonary to systemic flow of the QP to QS to oxygen delivery.

2550.799 -> As you may recall from the first lecture, as QP to QS goes up beyond a certain level,

2558.329 -> the blood that goes to the lungs effectively is blood that's stolen from the body. Given

2565.199 -> the fact the heart can only pump so much blood, and as a result, the total amount of O2 delivery--

2571.729 -> which is of course dependent upon not only arterial saturation, but also systemic blood

2577.18 -> flow-- tends to go down.

2579.209 -> These are computer-generated curves of the late QP to QS systemic O2 availability which

2585.759 -> is the same as delivery. And what it shows-- and I put a red circle on the graph to indicate

2591.789 -> the amount of total cardiac output that most neonates generally have. And as the QP to

2597.959 -> QS goes much more than a little bit less than 1, the total O2 delivery to the body actually

2606.059 -> falls even as the arterial saturation goes up.

2610.829 -> So it's important that these patients be managed in such a way that the natural tendency to

2616.709 -> have too much pulmonary bloodflow is not encouraged. And the way we do that is we avoid therapy

2622.499 -> that decreases pulmonary resistance, we avoid hyperoxia and alkalosis, both of which tend

2628.959 -> to vasodilate the lungs a pulmonary vascular bed.

2633.39 -> We avoid systemic hypertension. As systemic vascular resistance goes up, this tends to

2639.15 -> force more blood into the low resistance pulmonary circuit.

2643.359 -> Patients like this may also benefit somewhat from inotropic support in order to maximize

2647.88 -> a cardiac output. Diuretics can be helpful since they tend to accumulate some fluid in

2653.259 -> their body and their lungs.

2655.38 -> An occasional patient may benefit from sub-ambient oxygen, FiO2 in the 15-16 range or so. If

2662.489 -> in fact they show signs in decreased systemic perfusion we actually don't tend to use that

2668.39 -> very much in our institution, but under certain closely monitored circumstances it may be

2676.949 -> helpful.

2677.949 -> Summary. So to summarize, it's important to identify cyanotic lesions that seem likely

2686.969 -> to have congenital heart disease so that prompt diagnosis can be undertaken.

2695.16 -> One can certainly base diagnosis as best as possible on-- or base therapy-- as best as

2703.869 -> possible on specific diagnoses. And prostaglandin E1 when used appropriately can be very helpful.

2713.63 -> Even before one has a specific diagnosis, I should emphasize that for severely hypoxemic

2719.969 -> patients, generally speaking, the likelihood is greater that you will help than harm the

2726.17 -> patient with prostaglandin E1. So especially if one is dealing with life threatening hypoxemia,

2733.44 -> waiting for a specific diagnosis to initiate prostaglandin E1 would generally not be the

2739.029 -> appropriate thing to do.

2741.049 -> If the baby, upon being started on prostaglandin E1 becomes hypotensive or more hypoxemic,

2749.759 -> one may need to modify that therapy. But one should be relatively liberal in one's use

2755.099 -> of prostaglandin E1, absent specific contraindications.

2760.299 -> And finally, and this is a very important important point, some therapy, for example,

2766.89 -> optimizing hematocrit, minimizing O2 consumption, and promoting adequate systemic blood flow

2772.259 -> is helpful for just about anybody with severe hypoxemia and can be applied even when there

2778.369 -> isn't a specific diagnosis while one is waiting to do that.

2783.239 -> Thank you very much.

2785.589 -> Please help us improve the content by providing us with some feedback.

Source: https://www.youtube.com/watch?v=N6pvBSQMz-g