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Mark Twite, MA, MB, BChir, FRCP
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Luis Zabala, MD
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President's Message

Letter from the Editor


Contrast Agents and Pediatric Cardiac Catheterization

LITERATURE REVIEW

Etomidate: The controversy continues

CCAS Meeting Reviews

Morning Sessions

Afternoon Sessions

 

 

 

Meeting Reviews

2014 CCAS Annual Meeting Scientific Program Summary

Afternoon Session

By Gregory Latham, MD & Jeremy Geiduschek, MD

Session IV: Selected Posters for Oral Presentations

Despite the threat of a tornado, the afternoon session began with oral presentations by the authors of the top three submitted abstracts to CCAS. Dr. Shobha Malviya (CS Mott Children’s Hospital, Ann Arbor, MI) moderated the session. She noted that all three presenters are young investigators who are contributing excellent data to our field.

Justin Hamrick, MD (Johns Hopkins University, Baltimore, MD) presented “End-tidal directed cardiopulmonary resuscitation results in increased survival rates.” Per the American Heart Association (AHA), chest compressions should be performed at a rate of 100/minute and compress 1/3 the anterior-posterior diameter of the chest. However, achieving these goals is difficult during resuscitation. The AHA guidelines also indicated that end-tidal CO2 (ETCO2) is an indicator of cardiac output during compressions but that research is needed to confirm its role.

Dr. Hamrick and colleagues, using a piglet model, sought to elucidate its role by comparing ETCO2-directed versus optimized-standard CPR. Ventricular fibrillation was induced in the ventilated piglets, achieving a non-flow state for six minutes. In the ETCO2-directed group, rescuers varied compression depth, rate, force, and hand position to maximize the displayed ETCO2; in the standard group, a second observer assisted optimizing compressions by rate and depth per AHA guidelines. The authors reported that the rate of return of spontaneous circulation (ROSC) was significantly better in the ETCO2-directed versus optimized-standard CPR group (50% vs. 14%, p=0.043) in severe hypoxic arrest. It may also suggest that ETCO2-guided resuscitation allows a dynamic model of the efficacy of BLS.

Nate Greene, MD (Baylor College of Medicine, Houston, TX) presented two separate studies together, which built upon each other. The first, entitled “Effects of surgical palliation and perioperative brain injury on corpus callosum microstructural changes in the first year of life of infants with congenital heart disease,” utilized MRI diffusion tensor imaging (DTI) to assess microstructural changes in the corpus callosum of children who underwent congenital heart surgery during the neonatal period. Results of the preoperative and 3-6 month postoperative MRI-DTI scan demonstrated significant differential effect by the presence or absence of perioperative injury and of 1 ventricle versus two-ventricle repair. They concluded that microstructural changes in the corpus callosum may be a useful predictor of subsequent brain development and aid us in understanding neurodevelopmental outcomes.

The second study, entitled “Normalization of fractional anisotropy and apparent diffusion coefficient values facilitate appropriate comparison of corpus callosum microstructural changes in the developing newborn,” assessed 75 children with MRI-DTI who underwent neonatal repair of congenital heart disease. MRI-DTI scans again assessed microstructural changes in one-ventricle versus two-ventricle repair, but the study found that differences in post-conceptual age or age at the time of follow-up scan had significant differential effects to the results. The study therefore concludes that future MRI-DTI research must consider age and days between scans to draw accurate comparisons between groups. 

Lastly, Shannon Tew, MD (Duke University, Durham, NC) presented a study entitled “Natural history of non-immune mediated thrombocytopenia in pediatric open heart surgery.” As we all know, CPB causes qualitative and quantitative platelet defects. What we don’t know is the timing and duration of both the nadir and recovery of platelet counts postoperatively. This retrospective study evaluated 977 pediatric patients age 0-21 who underwent heart surgery with CPB. There was an inverse relationship between the Aristotle Complexity Score and nadir platelet count despite the complex patients having more intraoperative platelet transfusions. The authors are further investigating the relation between thrombocytopenia and post-operative non-fatal and fatal ischemic complications.

Q&A:

Session V: Clinical Practice

Nina Guzzetta, MD (Children’s Healthcare of Atlanta, Atlanta GA) moderated this exceptional and clinically relevant session. She explained that because of last year’s feedback, this section was designed to provide more clinically relevant discussions and that audience participation would be integral to the session. (Authors note: percentages of the audience’s response were recorded whenever possible. The slides were often displayed for only a moment, and many were missed.)

Bruce Miller, MD (Children’s Healthcare of Atlanta) presented an excellent session on Williams syndrome (WS). He began the presentation with the provocative statement, “Taking care of a child with Williams syndrome is like dealing with a ticking time bomb.” A murmur of agreement trickled through the audience. After a brief overview of the historical discovery, genetic mutation, and phenotype of WS, the critical cardiovascular abnormalities were reviewed. Because of mutation of the elastin gene, affected individuals can have varying degrees of supravalvar aortic stenosis (SVAS) and/or pulmonary stenosis, coarctation or hypoplasia of the aorta, peripheral pulmonary stenosis, renal artery stenosis, and coronary artery obstructions (ostial or intraluminal). Dr. Miller then used an illustrative case and audience participation to review the rest of the material. (The percentage of any answer by audience vote is noted…when it could be recorded in time!)

The case is an uncooperative 4-year old with WS presenting for a cardiac MRI.

Discussion: Patients with WS have a tenuous myocardial oxygen supply/demand relationship. The two conditions associated with the highest risk of sudden death are coronary obstruction and biventricular outflow tract obstruction. ECG can show ischemia, hypertrophy and prolonged QTc, (often seen in WS). Echo will define anatomy and severity of obstruction. However, the degree of SVAS is a poor predictor of coronary artery stenosis and sudden death, and coronary artery obstructions can occur in the absence of SVAS. The gold standard of coronary evaluation is a cath, but catheterization can be deadly because of blocking coronary blood flow, acute BVOTO, valve regurgitation and dysrhythmias.

Discussion: This decision is probably institution specific, but a benefit of cardiac anesthesia is their knowledge of resources and personnel in the heart center if the need arises to rally the troops.  At Dr. Miller’s institution, a cardiac anesthesiologist always provides the first anesthetic for a patient with WS.

Discussion: The goals are maintenance of sinus rhythm, heart rate, adequate preload, myocardial contractility, and SVR (phenylephrine is great) and then avoid acute elevations of PVR. There is no perfect anesthetic regimen. The best plan depends on various factors, including your familiarity with the anesthetic, the specific case, and the specific child. Titrate anesthetics slowly.  Instability can progress rapidly to cardiac arrest, which is extremely difficult to resuscitate.

Discussion: This varies from Dr. Miller’s practice where this patient would be induced in a cath lab.

The lecture closed with some other “tidbits” to consider. Children with WS have a 6-7 times higher incidence of prolonged QTc. There is also the potential for airway problems. Lastly, the possibility of association with malignant hyperthermia has been discussed because of a higher reported incidence of masseter spasm, but there is no apparent genetic correlation to suggest causation.

Nina Deutsch, MD (Children’s National Medical Center, Washington D.C.) expertly presented the next practical case, titled “Whose case is it anyway? The cardiac catheterization lab.” The case is as follows: a 15 year old girl, 126 kg, who received cardiac transplant at 11 years old for cardiomyopathy and has type II DM and OSA. She has a history of acute rejection 2 years ago and suffered ventricular fibrillation arrest in the cath lab at that time. She has now been non-compliant with her medications for several weeks. She presents with tachycardia and tachypnea, and she is scheduled for a cardiac cath with biopsy.

As highlighted in several recent studies, pediatric cath labs are seeing an increasing complexity of patients and procedures and a heightened risk of instability and complications. A 2005 study demonstrated a 9.3% risk of adverse minor and major events in the cath lab, including an 11.6% rate during interventional caths other than ASD or PDA closures. Therefore, skilled practitioners in sedation, airway management, and resuscitation are required, which also allows the cardiologist to concentrate on the procedure.
Returning to our case, an echo was shown that demonstrated biventricular failure.

Dr. Deustch stated that she would elect for medical management to stabilize ventricular function prior to having the patient undergo biopsy. She reviewed the decreased survival over time of the pediatric heart transplant recipients and the recipient causes of death. Emphasis was placed on the preoperative evaluation of the noncompliant patient. A complete H&P and review of medications should be obtained, looking for signs of rejection, including tachycardia, tachypnea, lethargy, hepatomegaly, new murmur, and new arrhythmias. Testing should include laboratory evaluation to assess end-organ damage, echo, and ECG. An echo can assess systolic and diastolic dysfunction, but cath is still the gold standard. Treatment of acute rejection includes steroids, increased immunosuppression, plasma exchange, IVIg administration, milrinone, or diuretics. This patient was sent to the ICU for steroid and milrinone therapy with marked improvement several days later with an LV EF of 30%.

A brief review of the risks of anesthetizing obese children ensued, highlighting the nearly 2-fold increased risk of critical airway events. However, there are not studies comparing the choice of ETT versus LMA in obese versus normal children.

Luis Zabala, MD (UT Southwestern Medical Center, Dallas, TX) anchored the session with a provocative discussion of “Cyanotic congenital heart disease: focus on long-standing hypoxemia, secondary erythrocytosis and coagulation.” Children with cyanotic heart disease suffer the physiologic affects of hypoxemia on every organ system, especially the hematologic and hemostatic systems. Chronic hypoxemia stimulates secondary erythrocytosis, which may be either compensated or decompensated. Decompensated secondary erythrocytosis occurs in the setting of ongoing erythrocytosis without improvement of tissue oxygenation, leading to potentially severe iron deficiency, hyperviscosity, microcytosis, and thus further worsening tissue oxygenation. In the hemostatic system, thrombocytopenia is the most common defect and is inversely proportional to the hematocrit. Platelets also have a shortened lifespan, and deficiency of multiple coagulation factors is common, especially impaired fibrinogen function and accelerated fibrinolysis. Hyperviscosity and vascular stasis predispose to widespread intravascular deposition of fibrin and platelet thrombi; whether this represents disseminated intravascular coagulation or not is unresolved. Given the potential coagulopathy, consideration should be given to perioperative strategies to lessen postoperative bleeding.

The case presentation is a six year-old with tetralogy of Fallot for repair. Evaluation reveals a baseline saturation of 74%, significant cyanosis and clubbing, and a hematocrit of 67%.

Current indications for isovolemic phlebotomy or intraoperative autologous blood donation include: (1) moderate to severe hyperviscosity symptoms and (2) Hct >65%. Of note, hypothermia exacerbates hyperviscosity, especially at higher hematocrit levels. Advantages of hemodilution include decreased viscosity (especially during hypothermia), improved blood flow at lower perfusion pressures, improved regional and cerebral blood flow, improved coagulation, and less postoperative bleeding. To date, there are no studies defining the optimal hematocrit for hypothermic CPB in patients with decompensated erythrocytosis, but targeting a hematocrit of 45% on CPB seems reasonable. However, isovolemic hemodilution should proceed with caution in patients with severe pulmonary stenosis or pulmonary obstructive vascular disease. The autologous blood can be transfused post-CPB, leading to improved coagulation and less donor exposure.

Coagulation deficits in patients with secondary erythrocytosis are complex and variable, and an overarching recipe cannot be derived. However, because deficiencies of antithrombin and other factors are possible, use of a patient specific heparin dose response is warranted. In addition, automated heparin/protamine titration can avoid the anticoagulant affect of excessive protamine. Children with secondary erythrocytosis are also likely to benefit from the administration of antifibrinolytic agents intraoperatively.

Intraoperative coagulation testing can be difficult in these patients. PT and aPTT do not reflect the interaction of plasma with cellular components of blood, such as platelets, and thus may lack some clinical relevance. Measurement of ACT in these children, as mentioned above, may also be problematic. Thus there is an argument for the value of thromboelastography (TEG) in these patients perioperatively to assess the dynamic hemostasis during this period. All components of clot formation and lysis can be evaluated with modifications of TEG, especially the functional fibrinogen assay, allowing perhaps improved interpretation of the specific coagulopathic deficits.

In the setting of post-CPB bleeding despite platelet transfusion, there is good evidence for the administration of cryoprecipitate. Evidence for administration of fresh frozen plasma is weak. Human fractionated factor concentrates have a better safety profile compared to blood, but there is no evidence in children.

Q&A:

Session VI: Focus on a Lesion: Pulmonary Atresia and Intact Ventricular Septum

Mark Twite, MA, MB, Bchir, FRCP (Children’s Hospital of Colorado, Aurora, CO) moderated the “focus on a lesion” session, which has become an exceptionally well-received tradition at the CCAS meetings. Dr. Twite began with a few audience participation questions that, in short, revealed that much could be learned about pulmonary atresia with intact ventricular septum (PA-IVS).

Larry Latson, MD, director of pediatric interventional cardiology and adult CHD at Joe DiMaggio Children’s Hospital in Hollywood, FL, began the three-part series with a thorough overview of anatomy, physiology, and diagnostic testing. Understanding the child’s specific anatomy and physiology of PA-IVS is so important because the pathway of repair is so varied depending on multiple factors. Major anatomic considerations that are critical to delineate in each case include characterization of the atretic pulmonary valve, right ventricle, tricuspid valve, ASD, PDA, pulmonary arteries, and coronary arteries. All of these structures impact the final pathway of palliation, repair, or transplantation.

Dr. Latson showed a series of photographs, echocardiograms, and angiograms to demonstrate the variable defects to the aforementioned structures. The tricuspid valve is usually abnormal, and TV size correlates well with RV size, which is usually hypoplastic to varying degrees. There is usually a small PFO or ASD, which is essential for survival if complete pulmonary atresia with no antegrade flow is present. These children are dependent on ductal patency for pulmonary blood flow and are thus started on prostaglandin at birth. Unlike PA with VSD, the pulmonary arteries in PA-IVS are usually normal, and multiple aortopulmonary collateral arteries are rare. If there is no tricuspid regurgitation, the RV pressure builds and has to go somewhere. RV to coronary connections (fistulas) form to relieve the RV pressure, which is clearly problematic. Coronary blood flow can become dependent on this retrograde flow (RV dependent coronary circulation [RVDCC]). The presence of RVDCC is a major determinant of planned surgical repair and patient outcome because sudden RV decompression can suddenly “steal” coronary artery pressure, especially if ostial stenosis has occurred at the aortic cusps. If RV pressure can be moderately reduced and ostial stenosis is not present, the RV-coronary connections tend to regress over time. Overall, the physiology is highly variable in children with PA-IVS, and echocardiography and cardiac cath are essential to delineate the anatomy.

Redmond Burke, MD, who is the chief of pediatric cardiovascular surgery at Miami Children’s Hospital, Miami, FL, expertly presented the surgical perspective. He began by reporting that 5-year survival rates of children with PA-IVS have now reached 80%, but it is uniformly fatal without repair. The greatest challenge is that PA-IVS is a rare lesion and has considerable heterogeneity, which leads to multiple approaches to palliation/repair without great evidence. Additional review of the anatomy from the surgeon’s perspective was mentioned. On average, tricuspid valve sizes are a -2 z-score. The RV is hypertrophied and hypoplastic in 90% of children and is severely hypoplastic in 60%. The RV can be unipartite, bipartite, or tripartite. RVDCC is present in 20% of cases, which requires single ventricle palliation, and mortality is high in this subgroup.

Dr. Burke reviewed his institution’s experience with 24 children over 10 years. They adopted a combined surgical and catheter-based approach whereby the initial treatment was dictated by the size and morphology of all the affected structures. Sixty percent of their patients had severe tricuspid valve and RV hypoplasia or RVDCC that required the single ventricle palliation pathway. They preferred to avoid CPB and start with ductal stenting in the cath lab, with or without balloon atrial septostomy depending on the size of atrial communication. Some of these children have an extraordinarily tortuous duct, which precludes stenting or is a risk of rupture during mediastinal dissection. If a Blalock-Taussig shunt (BTS) was required, they preferred to avoid CPB. Thirty seven percent of the patients were appropriate for biventricular repair. They prefer to perforate the pulmonary valve plate and perform balloon valvuloplasty in the cath lab as the first step, ensuring surgical standby. Often, they found it easiest to utilize a hybrid approach with the interventional sheath in the RV free wall. For outcomes, they demonstrated 100% survival in children undergoing biventricular repair and a 92% survival of all children at 6 years. Overall, these children require an individualized, collaborative approach, and the subgroup requiring a neonatal shunt has substantial early mortality.

Dr. Kirsten Odegard (Boston Children’s Hospital, Boston MA) finished this informative session with a excellent and practical discussion titled “Anesthetic considerations for palliative and definitive procedures.” Emphasis was made again on the fact that PA-IVS is a rare yet morphologically heterogeneous lesion, and anesthetic management depends on the anatomy, physiology, and surgical management at different stages. A review of the flow of blood through the heart was given, including the dependence of right-to-left shunt at the atrial level, left-to-right shunt at the ductal level, and the need to increase PVR to maintain cardiac output.

She presented a historical case of a 2.1 kg newborn with PA-IVS who was started on prostaglandin following birth and admitted to the CICU. At first the ECG was reassuring, but soon marked ST segment depression occurred. Why did this happen? As PVR fell, increased pulmonary “run off” across the duct created a steal from the coronary arteries. Additionally, RVDCC is deoxygenated blood, so RV decompression and pulmonary over-circulation must be avoided. Echocardiography of this child showed hypoplastic RV and tricuspid valve, no VSD, retrograde coronary blood flow, and ductal dependent pulmonary blood flow. The goals of anesthetic management in the cath lab are to treat them as if they have RVDCC, including maintaining RV pressure, systemic pressure, euvolemia to hypervolemia, and an adequate hematocrit. The cardiac cath demonstrated RV-coronary fistulae with narrow coronary ostia, so the baby was listed for transplant. Stenting of the PDA is often performed either as a bridge to transplant (i.e., presence of RVDCC) to avoid ongoing use of prostaglandin or performed after pulmonary valvuloplasty to maintain sufficient pulmonary blood flow. Anesthetic considerations of ductal stenting include stopping prostaglandin in advance, acute ductal thrombosis, PDA spasm, and stent migration.

In a case series of PA-IVS, pulmonary valve perforation was attempted in 60% of patients and was successful in 87% of cases. Seventeen percent suffered myocardial perforation, and 2 of 26 developed necrotizing enterocolitis post-catheterization. Other complications include arrhythmias. In a 2007 case series by Dr. Odegard of anesthesia-related cardiac arrests in children undergoing cardiac surgery, 41 cardiac arrests occurred, of which 11 were likely or possibly related to anesthesia. The highest procedure for cardiac arrest was truncus arteriosus (17.4/100 procedures) and BTS for PA-IVS (3.6/100 procedures).

In children undergoing BTS for PA-IVS, those with a good sized RV and normal coronaries normally do well. In those with RVDCC, however, hypotension on induction can cause ischemia. During diastole, “steal” occurs whereby the oxygenated blood runs unopposed into the RV, and during systole, deoxygenated blood from the RV perfuses the coronaries. The anesthetic goals are to maintain systemic and aortic root pressure, avoid reduction of PVR, optimize oxygen delivery (inotropes, high-dose fentanyl), and maintain adequate hematocrit. The critical moment of the operation is when the BTS is opened, which can suddenly drop aortic root pressure as “run off” occurs into the pulmonary bed until the PDA is ligated. Low diastolic pressures may persist and require treatment. If things go poorly and ECMO is considered, outcomes are not good.

A case series reported that seven of eight patients with PA-IVS who were placed on ECMO died. Those with RVDCC cannot tolerate ECMO weaning because decompression of the RV reduces coronary perfusion pressure. And negative pressure drainage of the right atrium creates a retrograde circular shunt, where the flow of blood is RV>RA>ECMO>Aorta>BTS>lungs or back into RV across regurgitant pulmonary valve after valvuloplasty. In a report of 32 children with PA-IVS undergoing a BTS, 100% with RVDCC died, and overall mortality was 19%, with no mortality after three months of age. Those with RVDCC should undergo transplant. One study of children with any degree of RV-coronary communication or coronary stenosis found that there was no regression of these lesions at the time of the Fontan procedure. Thus, the risk of ischemia remains in these children at the time of the Glenn and Fontan.

In children undergoing biventricular repair, 20-year survival is almost 91%, with 75% free of re-intervention. However, half of the patients had arrhythmias. Children with PA-IVS and single-ventricle repair have impaired exercise tolerance compared to those with biventricular repair. Thus, late clinical features depend on initia l presence of RVDCC and single versus biventricular repair.

Session VII: Posters-Viewing and Discussion

Poster viewing


Immediately after the plenary sessions, all were invited to view the posters while enjoying some food and drink. Drs. Glyn “Jumbo” Williams (Lucile Packard Children’s Hospital/ Stanford University, Stanford, CA), Lena Sun (Columbia University Medical Center, New York, NY), and Scott Walker (Riley Hospital for Children, Indianapolis, IN) moderated the well-attended session. For the interested reader, the abstracts can be viewed in their entirety HERE.

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