CCAS Meeting Review
By Faith Ross, MD
Seattle Children’s Hospital
This year the Congenital Cardiac Anesthesia Society celebrated its 10th anniversary with a fascinating and informative program that highlighted the history and the remarkable progress of congenital cardiac anesthesia over the past few decades. Program Director Nina Guzzetta, MD (Children’s Healthcare of Atlanta, Atlanta) and Co-directors Scott Walker, MD (Riley Hospital for Children, Indianapolis) and Mark Twite, MD (Colorado Children’s Hospital, Aurora) put together an impressive lineup of speakers addressing a variety of topics from neuromonitoring and hemostasis to outcomes data and quality improvement in pediatric cardiac anesthesia.
Session I: Controversial Aspects of Pediatric CPB
Moderator Victor C. Baum, MD (University of Virginia Children’s Hospital, Charlottesville) introduced the first session of the day, a discussion of controversial topics in pediatric cardiopulmonary bypass. Chandra Ramamoorthy, MBBS, FRCA (Lucile Packard Children’s Hospital, Palo Alto) opened the session by posing the question “Should NIRS be standard care for pediatric CPB?” The majority of the audience indicated that NIRS (cerebral oximetry) is routinely used for bypass cases at their institution and 71% felt that it should be standard care for these cases. Cerebral oximetry relies on the differential absorption of oxy- and deoxy-hemoglobin to provide an estimate of cerebral venous oxygen saturation. Commercially available devices differ in the type of light source (LED vs. laser), number of wavelengths, and proprietary algorithm. Normal cerebral oxygen saturation ranges from 60% to 70% on room air or 2/3 of the systemic arterial saturation and values less than 33-44% are associated with biochemical and electrical evidence of tissue damage.
There is a growing body of literature to support the utility of NIRS monitoring in pediatric CPB cases. A retrospective study by Austin et al demonstrated improved neurologic outcomes in children using cerebral oximetry to optimize cannula position and hemodynamic management during bypass. There are also several studies suggesting an association between low NIRS values and post-operative MRI abnormalities. Dr. Ramamoorthy concluded the session by drawing a comparison to pulse-oximetry. Despite the lack of concrete evidence that use of pulse oximetry decreases mortality, most anesthesiologists would agree that it is a vital monitor for anesthetized patients. Similarly, NIRS monitoring may play an important role in operative care even in the absence of level 1A evidence for benefit. NIRS monitoring may also prove useful in non-cardiac cases for patients with high risk of hemodynamic compromise.
Michael P. Eaton, MD (Golisano Children’s Hospital, Rochester) continued this engaging session with a review of antifibrinolytics. Infants with congenital heart disease are particularly vulnerable to the inflammatory and hemodilutional effects of cardiopulmonary bypass and are prone to significant coagulopathy in the post-operative period. As has been demonstrated in adult patients, exaggerated fibrinolysis may play a role in this coagulopathy and may prove amenable to improvement with antifibrinolytic drugs.
Recent clinical trials indicate that all of the recently available antifibrinolytic drugs (E-aminocaproic acid (EACA), tranexamic acid (TA), and aprotinin) are superior to placebo in reducing bleeding after CPB. Studies comparing the drugs to each other have had mixed results, but TA appears to have a slight edge in efficacy. Despite the fact that aprotinin was removed from the US market due to concerns about renal dysfunction in adult patients, the pediatric literature does not support this association in children. Dosing for these medications is highly variable, and pharmacokinetic and pharmacodynamic studies are needed to further define rational dosing schemes. Neonates require lower plasma levels of TA and EACA to inhibit fibrinolysis so dosing may need to be adjusted in this population. Loading doses of antifibrinolytics for pump prime are most logically dosed based on pump prime volume rather than patient weight. Dr. Eaton concluded that EACA, TA, and aprotinin all appear to be effective with some slight differences in side effect profile and drug shortages may be a determining factor for drug choice at individual institutions.
The session continued with a talk by Gina Whitney, MD (Children’s Hospital of Colorado, Denver) addressing the optimal hematocrit (HCT) for pediatric CPB. Red blood cell transfusion is associated with reduced survival after adult coronary artery bypass surgery and prolonged ventilation after CPB in children. The risks of transfusion must be weighed against the risk of inadequate oxygen delivery, particularly in infants and children with high baseline oxygen consumption. The Boston Hematocrit Trials attempted to answer the question of optimal hematocrit in pediatric CPB by comparing infants undergoing biventricular repair managed with a goal HCT of 20% or 30%. The group with hematocrit of 20% was found to have lower psychomotor and motor development indices than the group with HCT of 30%. A follow-up trial comparing infants randomized to HCT 25% or 35% found no difference in developmental indices. Combining the trials, there was a linear increase in psychomotor development indices up to a hematocrit of 23.5%. Thus, the optimal hematocrit for pediatric CPB (with hypothermia and pH-stat management) appears to be around 25%. Dr. Whitney cautioned that these results might not apply to normothermic or a-stat bypass cases or single-ventricle patients.
Session II: Basic Science and Clinical Application
Dr. Guzzetta introduced two fascinating lectures on right heart failure focusing on interventricular interactions and novel treatment strategies. Andrew Redington, MBBS, MRCP, MD, FRCP, Chief of Pediatric Cardiology at Cincinnati Children’s Hospital (Cincinnati), explained the physiology of RV-LV interactions in the normal and failing heart. RV and LV pressure-volume loops demonstrate a significant difference between LV and RV physiology. The right ventricle is subject to decreased stroke volume with minimal pressure change and has a limited ability to adapt to chronic stress. The RV is also four to five times more sensitive than the LV to changes in afterload.
Interventricular interactions play a strong role in biventricular function due in part to continuity of superficial myocardial fibers from the RV to the LV. Pacing of the LV alone can create robust PA flow even in the presence of an inert RV free wall; thus, by increasing LV contractility, RV contractility may be improved. This hypothesis has been tested by using aortic banding which mimics the effect of systemic vasoconstrictors on LV contractility and appears to have a beneficial effect on RV function. This somewhat surprising finding challenges the traditional role of vasodilators in RV failure. An advantageous effect on LV function may be similarly induced by placing a pulmonary artery band to increase RV contractility. This treatment was found to improve LV function in a neonate with dilated cardiomyopathy. The interaction between the RV and LV is likely not solely related to myocardial restraint and preload changes as the effect persists in the absence of intact pericardium. In chronic heart failure molecular signaling cross talk between the ventricles may play a role in fibrosis and remodeling.
Dr. Redington wrapped up his talk with a discussion of pulmonary hypertension (PHTN). RV ejection is prolonged in pulmonary hypertension and diminished diastolic time decreases both RV and LV filling, leading to worsening RV and LV performance. Tachycardia is especially problematic as it further diminishes diastolic time and decreases cardiac output. The need for inotropes is associated with a high risk of mortality in RV failure in patients with PHTN and vasoconstrictors without tachycardia-inducing effects (for example vasopressin) may be more useful in improving coronary perfusion without impairing ventricular filling.
Jeffrey R. Fineman, MD (UCSF Benioff Children’s Hospital, San Francisco) continued with a presentation of novel therapeutic strategies for the management of RV failure. Dr. Fineman reinforced the concept that the RV and LV have different responses to physiologic stress and respond to distinct pathologic mediators of hypertrophy and failure. Many treatments for LV failure have not demonstrated utility in RV failure but novel treatment options show some promise for this difficult to treat condition. Important goals in management include treatment of underlying disease process (ARDS, pulmonary embolism), optimization of preload while avoiding RV dilation, maintenance of systemic vascular resistance, avoidance of tachycardia, reduction of RV afterload, improvement of coronary perfusion pressure, and improvement in RV contractility.
To these ends, systemic vasodilators may be detrimental as they can lead to tachycardia and decreased coronary perfusion. Beta-blockers should be used with caution to avoid decompensation in vulnerable patients and renin-angiotensin-aldosterone inhibitors have not shown utility in human trials. Metabolic therapies such as pyruvate dehydrogenase kinase inhibitors and fatty acid oxidation inhibitors appear promising in animal studies and phosphodiesterase inhibitors have been shown to decrease RV hypertrophy and fibrosis. Ongoing research indicates a potential role for endothelin receptor antagonists in improving RV function and functional status. Cardiac resynchronization and invasive surgical treatments (atrial septostomy, ventricular assist devices, and lung transplantation to name a few) can be effective in selected patients. Hopefully some of these promising new therapies will prove useful in the management of this challenging condition.
Session III: Celebrating 10 Years of the Congenital Cardiac Anesthesia Society
Dr. Twite introduced two remarkably productive and influential anesthesiologists who treated us to a whirlwind review of the growth of congenital cardiac anesthesia and the progress of research since the inception of the specialty in the 1940s.
Robert H. Friesen, MD (Children’s Hospital of Colorado, Denver) presented a fascinating review of landmark articles that have been influential in the development of the field over the past several decades. (The extensive list of articles will not be reviewed here but can be viewed at www.ccasociety.org.) In 1946, Harmel and Lamont published the first paper addressing congenital cardiac anesthesia describing the management and complications in a series of patients undergoing BT shunt for congenital pulmonic stenosis. In 1958, Keats reported his experience with anesthetic complications for a series of 200 patients undergoing cardiopulmonary bypass. (He reported a mortality rate of 23% overall and 48% in patients less than 1 year old – dismal results by current standards.) Dr. Friesen highlighted several influential studies demonstrating the hemodynamic effects of fentanyl, propofol, and ketamine that paved the way for more hemodynamically stable cardiac anesthesia. More recent areas of investigative interest include bypass-induced coagulopathy and neurodevelopmental outcomes after pediatric heart surgery.
Paul R. Hickey, MD (Boston Children’s Hospital, Boston) presented a timeline of the development of cardiac surgery and anesthesia. Cardiac anesthesia essentially began with the first PDA ligation in 1938 (performed with mask cyclopropane). With the advent of cardiopulmonary bypass in the 1950s, intracardiac repair became possible in adult patients; however, outcomes in children after cardiopulmonary bypass continued to be poor throughout the 1960s and 1970 due to the large volume of the pump and difficulty scaling down from the adult to pediatric population. Thus, surgeons continued to use hypothermic circulatory arrest commonly in the 1960s to avoid the morbidity associated with early bypass pumps. Outcomes improved in the late 1970s, paving the way for the successful palliation of single-ventricle lesions beginning with the Norwood procedure in the early 1980s. Expanding surgical options have brought new ethical concerns as providers struggle with the balance between innovation and safe patient care.
Surgical and anesthetic complexity have increased in tandem and specialized pediatric cardiac anesthesia providers have become essential for the care of these complex patients. Anesthesia training has evolved to meet the demand for highly skilled providers with the development of advanced training in pediatric cardiac anesthesia. Congenital cardiac surgery and anesthesia are dynamic and growing fields that are likely to benefit from rapidly expanding technology. Development of new medications, microbubble oxygenators, bioengineered autologous valves, and stem cell treatment for hypoplastic ventricles promise to provide exciting challenges in the coming years.
Dr. Hickey concluded by sharing the lessons that he has learned in 45 years of practicing anesthesia: Teams are better than the sum of the individuals. Cardiac surgeons and cardiologists are people too. Today’s dogma will become yesterday’s mistakes. And the privilege of meeting the challenges of these patients is secondary only to the privilege of learning from one’s colleagues.
Session IV: Selected Oral Presentations
Dr. Walker began the afternoon session by introducing the three top posters chosen for oral presentation.
Sarah Franklin, MS4 (Emory University School of Medicine, Atlanta) presented research on the optimization of thrombin generation with 4-factor prothrombin complex concentrates (PCCs) Kcentra and FEIBA. Franklin and her colleagues evaluated baseline, post-CPB, and post-transfusion thrombin generation curves from 15 neonates undergoing complex cardiac repairs with cardiopulmonary bypass. They found that ex-vivo addition of Kcentra or FEIBA to the samples increased peak thrombin generation in the post-CPB and post-transfusion samples and FEIBA (but not Kcentra) significantly shortened the lag time for thrombin generation in the post-transfusion samples. She concluded that the addition of 4-factor PCCs to neonatal plasma has the potential to enhance thrombin generation after CPB and PCCs may be useful in augmenting hemostasis in neonates undergoing complex cardiac procedures.
Jake Scott, MD (Children’s Hospital of Wisconsin, Milwaukee) presented an analysis of the incidence and risk factors for acute kidney injury following Fontan procedure. He noted that AKI is apparent in 15-20% of patients after cardiopulmonary bypass and is associated with increased morbidity and mortality. Children undergoing Fontan procedure are likely at increased risk of AKI due to elevated systemic venous pressure. Dr. Scott’s group found that AKI is common after Fontan completion (54%), and half of Fontan patients who develop AKI meet criteria for severe AKI. Risk factors for AKI in this population include decreased renal perfusion pressure, longer CPB time, high vasoactive medication requirement, decreased urine output, and large volume albumin administration.
The final poster, presented by Roby Sebastian, MD (Nationwide Children’s Hospital, Columbus) examined the impact of storage techniques on platelet count and function after acute normovolemic hemodilution (ANH). The protocol involved withdrawal of approximately 10-20% of the circulating volume from 23 pediatric Jehovah’s Witness patients prior to surgical incision. Platelet count and function were measured after blood collection and prior to reinfusion. Nineteen of the 23 patients showed no change in platelet function and the average decrease in platelet number was 13 +/- 41 x 1000/mm3. The duration and type of storage container had no impact on platelet count or function. Dr. Sebastian concluded that ANH has little effect on platelet count or function and patients who are treated with ANH are less likely to require allogeneic blood products.
Session V: The Congenital Cardiac Database and Clinical Practice
Emad Mossad, MD (Texas Children’s Hospital, Houston) moderated an informative discussion of the Congenital Cardiac Database and the role it plays in clinical practice.
Sara Pasquali, MD, MHS (C.S. Mott Children’s Hospital, Ann Arbor) began the session with a discussion of data-driven approaches to quality improvement in health care. Recent changes in health care policy, particularly the development of a pay for performance reimbursement structure, designation of centers for excellence, and public quality reporting initiatives have increased the need for quality data analysis and active collaboration between centers to improve outcomes. The STS database has revealed significant variation among centers in practice patterns and patient outcomes. By focusing on the variability in practice and its effect on outcomes groups can identify effective practices of top-performing centers and disseminate this information nationally. Data analysis has traditionally been plagued by the confounding effects of procedural case mix and heterogeneity of patient characteristics. Recent efforts to correct STS data for these factors have proved useful in providing more meaningful feedback to participating sites. There are currently several databases, including STS that are collecting data relevant to the care of patients with congenital cardiac disease. Utilization of feedback from these databases along with inter-site collaboration has the potential to improve patient care nationally and reduce cost.
David Vener, MD (Texas Children’s Hospital, Houston) presented an overview of the evolution and current state of the STS database and plans for future development. From January 2010 through December 2014, 115 of 122 US congenital cardiac surgery programs have participated in the STS database. Currently 48 anesthesia programs participate and much of the data includes surgical and demographic information only. Participation in the database provides contributing sites the opportunity to receive feedback regarding adverse events and outcomes and may provide valuable information regarding practice patterns at other institutions. The database has grown significantly over the past few years, from 20,000 cases in the spring of 2012 to almost 60,000 in the fall of 2014. Bypass cases are most heavily represented, but non-cardiac surgery and cardiac catheterization cases are increasingly reported. Upcoming changes to the database include consolidation of blood product reporting, revision of medication reporting, and the establishment of national standards of care.
Session VI: Focus on a Lesion: Total Anomalous Pulmonary Venous Connection (TAPVC)
Moderator Peggy McNall, MD (University of North Carolina, Chapel Hill) kicked off the Focus on a Lesion Session with a series of audience questions about total anomalous pulmonary venous connection.
Timothy Slesnick, MD, a pediatric cardiologist and director of cardiac MRI at Children’s Healthcare of Atlanta (Atlanta), began the discussion of total anomalous pulmonary venous connection with a description of the embryology and pathophysiology of TAPVC. TAPVC results when the common pulmonary vein fails to connect with the pulmonary venous plexus and the primitive embryologic connections to the common cardinal and umbilicovitelline systems persist. Thus all pulmonary venous blood flow returns anomalously to the systemic veins or directly to the right atrium. Four types of TAPVC – Supracardiac, Cardiac, Infracardiac, and Mixed - are classified based on the location of the pulmonary venous connection with the systemic venous circulation. Obstruction of pulmonary venous drainage (nearly universal in the infracardiac type) results in profound cyanosis and circulatory instability. An open atrial connection is absolutely essential in these patients as it is the only route of blood supply to the systemic circulation via the left ventricle.
Transthoracic echocardiography is the mainstay of diagnostic imaging for this lesion. Transesophageal echocardiography is rarely used as the echo probe may obstruct the pulmonary venous confluence and cause profound instability. All pulmonary veins should be visualized and spectral Doppler should be used to evaluate for obstruction. CT angiography and cardiac MRI may also provide valuable information particularly in cases where TTE visualization is difficult. Cardiac catheterization is not typically used unless intervention is planned or anatomy is not well defined by other modalities.
Daniel Velez, MD, a congenital cardiac surgeon from Phoenix Chiildren’s Hospital (Phoenix), presented his perspective on the surgical management of TAPVC. Surgical repair is typically performed with circulatory arrest in critically ill infants. Surgical goals include the elimination of anomalous connections, establishment of pulmonary venous drainage into the left atrium and closure of intra-cardiac shunts. Early post-operative complications include pulmonary edema, pulmonary hypertensive crisis, and phrenic nerve damage. Pulmonary venous obstruction, anastomotic stricture, and pulmonary vein stenosis are relatively common long-term sequelae. Patients with pre-operative acidosis, pulmonary venous obstruction, high pulmonary vascular resistance, young age, small left ventricle, major associated anomalies, or infracardiac or mixed type connection are at increased risk for morbidity and mortality.
Andrew Wolf, MBBChir, MD, FRCA (Bristol Royal Children’s Hospital, Bristol) then described the major anesthetic considerations for these very challenging patients. He stressed the importance of understanding of the anatomy and physiology of individual patients and the lack of evidence-based data to guide clinical practice. Timing and nature of presentation are variable depending on the location of drainage and degree of obstruction. Patients with obstructed TAPVC present in extremis with shock and respiratory failure in the neonatal period. They have significant interstitial edema with lymphatic dilation and pulmonary hypertension. Nitric oxide and inotropic support may be initiated pre-operatively; however, the ability to improve the condition of these patients with pre-operative support is limited and they should be taken urgently to the operating room for surgical repair. Anesthetic care should be tailored to minimize pulmonary edema and pulmonary hypertension and maintain adequate blood pressure and coronary perfusion. Pulmonary hypertensive crisis is not uncommon in the post-operative period, even with adequate surgical repair, and nitric oxide, high inspired oxygen concentration, mild hypocapnea, and phosphodiesterase inhibition are key components of post-operative management.
The meeting concluded with a review of posters and a reception celebrating the 10th anniversary of the CCAS. Posters are available for viewing at www.ccasociety.org.