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Editor
Courtney A. Hardy, MD
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Co-Editors
Mark Twite, MD, BCh
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Stuart R. Hall, MD
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INSIDE

President's Message

Letter from the Editor


An Update on the Fontan Operation: Morbidity, Mortality and Late Complications

An Interesting Case: A Case of an  Unexpected Airway Difficulty in the Cardiac Operating Room

Thanks to Our 2011 Exhibitors

LITERATURE REVIEW

Systematic Review: Benefits and Harms of In-Hospital Use of Recombinant Factor VIIa for Off-Label Indications

 

 

CCAS Meeting Review

CCAS Reception photos

Attendees Celebrated the 5th Anniversary of CCAS at a Reception in San Diego. 

By Mark Twite, MD, BCh

A shining educational program put together by Drs. James DiNardo, Anshuman Sharma and Suanne Daves equaled the fantastic San Diego weather. This fifth annual meeting of the CCAS produced interesting topics and excellent speakers.

Dr. Chandra Ramamoorthy moderated the first session ‘Living with Hypoxia.' The first speaker, Dr. Mike Crowder, from the departments of anesthesiology and developmental biology, Washington University, St Louis, kicked off the morning with a brilliant introduction to hypoxic preconditioning. The speaker reminded us that we already see evidence of hypoxic/ischemic preconditioning in clinical practice with improved outcomes in patients who have angina attacks prior to their myocardial infarctions, so called ‘stuttering infarcts.'

Likewise, transient ischemic attacks preceding a stroke result in better outcomes compared to a sudden unheralded stroke. These protective mechanisms have two phases, immediate and delayed. The delayed response is likely the result of gene transcription/translation and protein production. The difficulties are working out the protective mechanisms of ischemic preconditioning.

Dr. Crowder’s lab is studying the nematode C. elegans and how misfolded proteins are an inducer of hypoxic preconditioning. This is clearly an exciting possibility for protection in the operating room for numerous surgical procedures. The challenge is how to translate such findings into clinical practice and identify a relative innocuous inducer of preconditioning.

The second speaker, Dr. Christopher Calderone from The Hospital for Sick Children, Toronto, helped translate some of the basic preconditioning science into clinical reality. In a very exciting presentation the speaker discussed two major phenomenon of ischemic preconditioning: timing and location of the stimulus.

With respect to the timing of a stimulus for ischemic preconditioning evidence supports pre, per and post conditioning protective responses. From a clinical application standpoint this is crucial because we are usually unable to predict the timing of ischemic insults (other than in the operating room) and the ability to intervene during or even after an ischemic insult is very attractive for clinical practice. Experimental data suggests that the effects of ischemic preconditioning occur largely by modulating responses to reperfusion. However, this still requires direct local ischemia of the target organ that is technically difficult and has limited clinical utility.

The second phenomenon is the concept of remote ischemic preconditioning. This is where transient ischemia of a wide range of tissues induces a systemic effect with multi-organ protection against subsequent prolonged ischemia-reperfusion. This preconditioning at a distance recapitulates the levels of protection seen with local preconditioning and has similar early and late phases of protection. The mediator of this remote preconditioning appears to be a dialyzable cardio-protective substance in the blood, factor X. This substance confers protection at the mitochondrial level in organs throughout the body.

Dr. Calderone illustrated this remote ischemic conditioning in elite swimmers. Two groups of swimmers had blood pressure cuffs inflated on their arms prior to swim practice. However, in only one group was the cuff inflated above systolic pressure to achieve distal limb ischemia for four cycles of 5 minutes each. In this intervention group the swim times improved by 0.6 seconds compared to the placebo group.

This is compelling evidence that remote ischemic conditioning can work and is a clinical reality. Dr. Calderone concluded his excellent talk emphasizing that remote ischemic preconditioning is becoming a ‘grass roots’ movement. It is inexpensive, safe and does not need large pharmaceutical company involvement. The writing is on the wall; the translation of remote ischemic preconditioning into clinical practice will happen.

The final talk in the first session was the anesthetic management of a child with long standing hypoxemia. Dr. Scott Walker from Riley Children’s Hospital, Indianapolis, provided an entertaining insight into the clinical problems associated with long standing hypoxemia. Dr. Walker made excellent use of the audience response system to demonstrate the audiences’ current knowledge base on this topic.

Clearly, some of us needed to listen closely to what followed! Dr. Walker used a case study, a patient called Asma, to illustrate many well-established clinical points. He started with monitoring, reminding us that pulse-oximetry OVER estimates oxygen saturations at lower levels, especially below 80%. End-tidal carbon dioxide (ETCO2) measurements are also affected in children with right-to-left shunts.

Not only does shunted blood carry de-oxygenated blood but high CO2 levels as well. This represents CO2 that bypasses the lungs and results in an INCREASED ETCO2 to PaCO2 difference. In fact this difference increases by 2-3 mmHg for every 10% reduction in SaO2. Dr. Walker continued the clinical pointers discussing polycythemia, coagulation issues and how chronic hypoxemia affects the heart and respiratory systems as well as a child’s growth and neurological development.

The first session was concluded with Dr. Ramamoorthy moderating questions from the audience. Many in the audience wanted to hear how anesthetic gases may confer a protective conditioning response and if there may be any downsides to the innocuous appearing remote ischemic preconditioning such as activating the inflammatory response. There were also questions about monitoring children with chronic hypoxia and the effects this may have on NIRS.

Dr. Helen Holtby from the Hospital for Sick Children, Toronto, moderated the second session on Cardiac MRI. The first speaker, Dr. David Parra from the division of cardiology at Monroe Carrel Jr. Children’s Hospital, Vanderbilt, provided a cardiologist's viewpoint of cardiac MRI. The number of cardiac MRIs in children has increased dramatically over the past decade. There must, therefore, be some advantages to MRI over more conventional modes of imaging such as echocardiography and cardiac catheterizations.

Dr. Parra clearly described the limitations of these conventional modes. Acoustic windows and the position and course of extra-vascular structures limit echocardiography. It also makes geometric assumptions, for example of LV shape to determine ventricular function. Cardiac catheterizations are invasive, expensive and expose the child to radiation. Cardiac MRI, on the other hand, is non-invasive and in a single study can provide accurate information on; anatomy, ventricular function, blood flow quantification (Qp:Qs) and tissue characterization. Dr. Parra illustrated many of these points with excellent images and case studies.

The second speaker, Dr. Kirsten Odegard from Children’s Hospital, Boston, discussed the challenges of anesthetizing a patient for cardiac MRI. Dr. Odegard provided an excellent synopsis of the challenges anesthesiologists face in the MRI suite.

These challenges include: an offsite location, monitoring difficulties, complex physiology and limited cardiac reserve in patients with congenital heart disease and the austere MRI environment. Dr. Odegard reminded us that cardiac MRI is not really non-invasive for most children who require general anesthesia and endotracheal intubation for immobility and breath holds. She emphasized the importance of a clear cardiac MRI resuscitation algorithm and the importance of simulated scenarios for all providers in the MRI setting.

Dr. Holtby concluded the second session by moderating questions from the audience. Many people wanted to know how essential breath holding really was for MRI image acquisition. This seems to be a common theme of irritation for many cardiac anesthesiologists as it usually involves the provider spending a long time in the MRI room and potential instability of the patient. Dr. Parra responded that breath holds were essential to decrease motion artifacts and actually shortened already long scan times. Others asked if it was indeed safe for anesthesiologists to spend many accumulated hours in the MRI scan room. The issue of radiologist’s presence at a ‘time-out’ was also raised, as it appears this is not common practice at most institutions.

The third session, moderated by Dr. Suanne Daves from Vanderbilt University, had three speakers present the ‘sickest of the sick.' The first speaker in this session, Dr. Emad Mossad from Texas Children’s Hospital, Houston, presented a three month-old child with dilated cardiomyopathy for evaluation for heart transplantation.

Dr. Mossad began by reviewing the epidemiological data for dilated cardiomyopathy reminding us that it is the most common form of cardiomyopathy and more prevalent in male, black infants and in the north east region of the USA. The essential clinical characteristics of this disease include poor ventricular compliance of both ventricles (ventricular interdependence) and baseline tachycardia.

These infants are at high risk for arrhythmias and sudden death as well as the manifestations of poor cardiac output. A pre-transplant evaluation usually involves echocardiography and a visit to the cardiac catheterization lab for hemodynamic data, determining reversibility of any pulmonary hypertension and a myocardial biopsy. Dr. Mossad concluded by emphasizing the importance of airway management, fluid balance, maintaining sinus rhythm, good communication with all providers and an appropriate location to recover these fragile patients.

The second speaker in this session, Dr. Alexander Hughes from Vanderbilt University, discussed a child with Williams syndrome presenting to the cardiac catheterization lab for potential balloon dilation of critical AS and PS. Dr. Hughes made good use of the audience participation system and provided an excellent review of Williams syndrome. He reminded us that it is caused by a micro-deletion of genetic material on long arm of chromosome 7 in an area of the elastin gene.

The terrifying feature of this disease is the aortic stenosis that usually involves the coronary ostia. Children with Williams syndrome are prone to sudden death especially under general anesthesia. This is a result of a mismatch in the increased oxygen demand from the hypertrophied left ventricle myocardium and the decreased blood supply from narrowed coronary artery ostia. Children with supra-valvar aortic stenosis and peripheral pulmonic stenosis, the hallmarks of Williams syndrome, are at highest risk for sudden death.

Interestingly, the period of emergence and recovery from anesthesia may constitute a period of increased risk, which raises the important questions of who should anesthetize these children and where should they be recovered. Dr. Hughes concluded by emphasizing that planning was key for a safe anesthetic in children with Williams syndrome. They should be done in day time hours, preferably first case of the day to minimize length of time without clear fluids, and particular attention should be paid to maintaining sinus rhythm, pre-load and contractility. These children should probably then have a ‘safe landing’ in the ICU for recovery.

Dr. Nina Guzetta from Emory presented the final talk in this session on a three-month-old infant with a BT shunt brought to the cardiac catheterization lab with severe persistent desaturation. Dr. Guzetta began her talk by quoting Aristotle; “We are what we repeatedly do. Excellence, then, is not an act, but a habit." As with Dr. Guzetta’s previous talks at this conference we could argue that she has developed a habit of presenting excellent talks!

Dr. Guzetta began with why children receive modified BT shunts and the fact that we need to think of how pulmonary blood flow changes as the child grows with this shunt. In the newborn the shunt is essentially too large and it functions as a ‘simple’ shunt where the outflow resistances are the primary determinants of the degree of shunting.

In other words, in a small baby the Qp:Qs is often greater than 1. However, as the baby grows the shunt becomes relatively smaller with respect to the size of the infant and eventually the Qp:Qs will be less than 1. The differential diagnosis of a desaturated infant with a BT shunt can be considered as acute or chronic. Acute desaturation often indicates thrombosis and a common etiology is dehydration from a viral gastroenteritis. Chronic desaturation on the other hand simply develops over time as the infant outgrows the shunt.

However, in both situations other things should be considered in the differential diagnosis including other cardiovascular issues such as a restrictive ASD, strictures at the shunt anastomosis site, pulmonary vein stenosis and pulmonary issues such as chronic lung disease in premature infants, pulmonary hypertension and reactive airways disease. Dr Guzetta reviewed why shunts might become occluded. Most of the time it is due to thrombosis which may be caused by any alteration in Virchow’s triad; stasis (dehydration, hypotension, polycythemia), endothelial injury (surgery) and hypercoagulability (post-op). 

Infants with shunt occlusion usually present acutely to the cardiac catheterization lab for urgent intervention. It is important for the pediatric anesthesiologist to be aware of the differential diagnosis and the pathophysiology of the shunt occlusion and how this impacts the underlying congenital cardiac disease. Management usually involves prompt endotracheal intubation and ventilation, volume resuscitation and blood pressure support until the shunt can be re-opened.

Dr. Daves concluded the third session by moderating questions from the audience. The issues of anti-coagulation strategies for infants with BT shunts was discussed as well as cardiac arrests in patients with Williams syndrome who do not have supra-valvar AS. It was emphasized that echocardiography may miss coronary artery abnormalities and it is safe practice to assume every child with Williams syndrome may have coronary involvement and to carefully consider the safest setting for elective surgery.

Session IV gave three young physicians the opportunity to showcase their research. Dr. Manchula Navaratnam from Stanford eloquently presented the first poster in a Queen’s English dialect. Dr. Navaratnam’s poster was entitled ‘Doppler derived stroke distance is a useful indicator of low ventricular function in children.' Traditional echocardiographic measures of contractility such as ejection fraction (EF) and fractional shortening (FS) are of limited value in children with abnormal ventricular geometries.

Dr. Navaratnam studied a Doppler derived measure, left ventricular outflow tract velocity time integral (LVOT VTI), which is independent of ventricular geometry, as a surrogate marker of ventricular function. Her research concluded that LVOT VTI when indexed to BSA correlates with FS and EF across a range of LV function in children with dilated cardiomyopathy.

The second poster was presented by Dr. Luis Zabala from Arkansas Children’s Hospital and was entitled ‘Transesophageal Doppler measurement of renal arterial blood flow velocities and indices in children’. Dr. Zabala has developed a novel use of TEE in children to look at Doppler derived renal blood flow indices.

The prospective study looked at healthy children undergoing ASD device closure in the cardiac catheterization lab and compared TEE derived measures with trans-abdominal renal ultrasound measures (the current gold standard). The results showed significant agreement between the two methods of measurement and provide another role for TEE to assess renal parameters in the cardiac operating room.

Dr. Aymen Naguib from Nationwide Children’s Hospital presented the final poster on ‘Hemodynamic and cerebral saturation changes during SVT episodes.' This prospective study compared the changes in arterial blood pressure with changes in cerebral perfusion in children having induced episodes of SVT in the electrophysiological lab. The study showed that changes in systolic and mean arterial blood pressure correlate with changes in NIRS during SVT. Dr. Naguib concluded that NIRS in the EP lab could negate the need for invasive pressure monitoring by providing a useful measure of end organ perfusion.

The three poster presenters should be congratulated on excellent research studies. Dr. Courtney Hardy from Children’s Memorial Hospital, Chicago, was an outstanding moderator for this session, keeping the presenters on time and asking insightful questions.

Dr. Glyn Williams from Stanford moderated the fifth session on early extubation and pediatric cardiac surgery. The first speaker in this session, Dr. Jon Meliones from Duke presented ‘Respiratory mechanics after cardiopulmonary bypass.'  Dr. Meliones expertly reviewed the triggers and mechanisms of respiratory failure post cardiac surgery.

The systems that contribute to respiratory issues include; cardiopulmonary bypass, hemodilution, hypothermia, deep hypothermic circulatory arrest or low flow cerebral perfusion bypass and reperfusion injury. All of these systems act in part via the systemic inflammatory response with the resulting consequences of parenchymal and vascular lung injury. Dr. Meliones discussed treatment strategies for such lung injury including ventilation strategies that avoid over-distension of the alveoli, surfactant replacement and inhaled nitric oxide.

The second speaker in this session, Dr. Alexander Mittnacht from Mount Sinai, New York, presented the pro arguments for early extubation after cardiopulmonary bypass. The first question of can we extubate patients early (within six hours) after surgery involving cardiopulmonary bypass has clearly been answered by the existing literature – yes we can.

However, whether we should extubate patients early requires more thought. The benefits appear to be fewer pulmonary complications, better post-operative hemodynamics, less sedation required, happier parents and less overall hospital costs. There are also clinical benefits for certain populations, such as in children who have had a Glenn or Fontan procedure where permissive hypercapnia and spontaneous ventilation may improve cardiopulmonary dynamics.

Dr. Mittnacht’s excellent arguments supporting early extubation seem to have one weakness, the ‘would we’ question. Often it is the personal preferences of the anesthesiologist, surgeon or intensivist not to extubate children early after surgery for congenital heart disease. Despite the scientific evidence supporting early extubation it may actually come down to local preferences as to whether it is actually done.

The final speaker in the session was Dr. Frank McGowan, formerly at Boston Children’s Hospital but now at Medical University of South Carolina.  Dr. McGowan presented the con side of early extubation ‘What’s the hurry: pathophysiology the fast trackers don’t want you to know’. The strongest argument that Dr. McGowan presented was that positive pressure ventilation improves cardiac function and may help in a child with low cardiac output syndrome post-operatively. While his presentation was entertaining, this giant in pediatric cardiac anesthesiology seemed to struggle to counter some of Dr. Mittnacht’s well thought out arguments.

Dr. Williams concluded this session with a lively debate from the audience and panelists. Dr. Meliones answered several questions about surfactant, which seemed to reflect that many in the audience do not administer it as frequently as he does! The use of an ICU ventilator in the operating room instead of the anesthesia machine ventilator was also discussed.

Many questions were asked about other factors that may influence fast-tracking such as surgical skill and post-operative bleeding, low flow versus no flow perfusion, lung cooling during cardiopulmonary bypass, ultra-filtration and neuraxial analgesia. Clearly the debate was not settled at the end of this session and it may be a topic that is worth revisiting at a future meeting.

Session VI was moderated by Dr. James Dinardo from Children’s Hospital Boston, and followed the theme of prior CCAS meetings of discussing the pathology, surgical repair and echocardiographic findings of a specific congenital heat lesion. The lesion at this meeting was Tetralogy of Fallot.

The first speaker in this session was Dr. Angela Sharkey from Washington University, St. Louis.  Dr. Sharkey provided an excellent review of the pathological features of TOF supported by outstanding specimens. The ability to see as well as hear about the specific defects really helps in the understanding of these lesions. Dr. Sharkey reviewed the four anatomic malformations that are the hallmark of TOF; anterior mal-aligned VSD, aortic over-ride, and under-development of the structures of the right ventricular outflow tract including the main and branch pulmonary arteries as well as the pulmonary valve.

The spectrum of TOF includes those with mild PS, the so-called ‘pink tet’ to those with pulmonary atresia with or without aorto-pulmonary collaterals. Dr. Sharkey then reviewed the surgical approach to TOF pointing out that it is dependent on the location and severity of right ventricular outflow tract obstruction. She also reviewed associated cardiac anomalies that can impact the surgical repair as well as associated extra-cardiac anomalies. Dr. Sharkey explained how the differentiation of TOF from double outlet right ventricle (DORV) relies on the assessment of the presence of bilateral subvalvar conus.

The next speaker, Dr. John Lamberti, a pediatric cardiac surgeon from Rady Children’s Hospital, San Diego, presented the surgical options for repair or palliation in TOF. His historical timeline provided a perspective on how surgical repairs have improved over the past decades. Dr. Lamberti’s talk was a nice balance between surgical techniques and the larger picture of intra-operative management.

His comments such as ‘NIRS is valueless if you ignore it’ and ‘amiodarone is like the EP doc in battle’ are difficult to forget! Dr. Lamberti concluded by discussing the management of TOF at his local hospital and emphasized that an integrated approach from everyone involved is essential for success.

Dr. Wanda Miller-Hance from Texas Children’s Hospital, Houston concluded this session with a detailed description of the echocardiographic findings in TOF. Her talk was supported with outstanding echocardiographic cine images and complemented the preceding speakers perfectly. She emphasized that the primary goal of the initial echocardiographic evaluation is to outline the anatomic abnormalities in detail, evaluate associated pathology and perform a physiologic assessment. Dr. Miller-Hance clearly explained this evaluation using the Anderson segmental morphologic analysis approach to both TOF and DORV.

Dr. Anthony Clapcich from Children’s Hospital of New York wrapped up a long day with a fun session of jeopardy. It is very clear that Anthony invests a huge amount of time and effort into producing very interesting questions. His answers are always well researched and presented. Unfortunately, the session was a little rushed as the earlier sessions had run over but this did not diminish the excellent content. Hopefully, next year, better time keeping will give this session the time it deserves.

The evening cocktail party provided a chance to soak up some sunshine, celebrate a very successful meeting and catch up with friends in a very congenial setting on the marina. All of the organizers should be thanked for putting on such an excellent meeting – everything from the speakers to the food was outstanding. Even the weather cooperated!

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