Meeting Reviews

Session III: Selected Poster for Oral Presentation

By Rajeev Wadia, MD

Moderator: Gregory J. Latham, MD (Seattle Children’s Hospital, Seattle)

Once again, it comes as no surprise that there were several outstanding abstracts chosen for the selected Oral Presentation Session this year. With research burgeoning in our field, the future is bright. Below is a brief description for each of the posters presented with the asterisk (*) indicating the presenter.

Title: The Effect of Perioperative Anemia on Cardiac Surgical Patients Undergoing Cardiopulmonary Bypass

Authors: Chu R, DiGiusto M*, Nadkarni A, Goswami D (Johns Hopkins University)

Description: Preoperative anemia is an independent risk factor for morbidity and mortality in adults undergoing cardiac surgery and children having non-cardiac surgery. Therefore, this group retrospectively evaluated the impact of preoperative anemia on the rate of complications. This was a single-center retrospective study over a 40-month period of all pediatric patients undergoing cardiac surgery, excluding patients who underwent urgent/emergent procedures and those receiving preoperative ECMO support.

Using the World Health Organization (WHO) definition for anemia, the rate of preoperative anemia in the cohort of patients was 67%, with a mean hemoglobin value of 9.8 +/- 0.1 gm/dL. Those with anemia were more likely to have had a previous cardiac operation (32.2% vs 13.1%, p-value <0.01) and higher age at surgery (9.3 +/- 0.4 years of age vs 6.5 +/- 0.5 years of age, p-value <0.01).

Their results showed that children with preoperative anemia had more major postoperative complications (OR 1.43, 1.26-1.66) and an increased hospital length-of-stay (OR 1.21, 1.02-1.44). These outcomes were fascinating, but the authors state they are limited due to the retrospective nature of the study. Further analysis is needed to determine if the observed morbidity was due to transfusion (in those whom received it) or the preoperative anemia itself. In addition, postoperative blood utilization was unable to be controlled for at the time of abstract submission.

Title: Potential Neuroprotection Induced by Intraoperative Administration of Dexmedetomidine and Ketamine to Infants with Complex Congenital Heart Disease

Authors: Ibrir K*, Desnous B, Marandyuk B, Lenoir M, La KA, Zhang E, Mahdi Z, Chowdhury R, Dehaes M, Poirier N, Birca A, Côté G, Pinchefsky E (Université de Montréal, Québec Canada)

Description: The aim of this study was to evaluate the effect of intraoperative administration of dexmedetomidine and/or ketamine on evolution of the postoperative electroencephalogram (EEG) in neonates with congenital heart disease (CHD). The authors performed a retrospective study of neonates (<44 wks AGA) who underwent cardiac surgery and had a postoperative EEG recording for at least 24 hours. BrainVision software was used to quantify the EEG discontinuity index (defined as the percentage of the EEG that has a peak-to-peak amplitude difference of <25 μV), which is not normally present in healthy term newborns. Fifty total neonates were reviewed, with seven in the dexmedetomdine only group, ten in the ketamine only group, 20 in the dexmedetomdine + ketamine group, and 13 in the control group (neither dexmedetomidine nor ketamine).

Their results showed an increase in the postoperative EEG discontinuity index up to the 24 hours after bypass in all groups. However, the intraoperative administration of either dexmedetomdine only or ketamine only resulted in lower average discontinuity index (better postoperative EEG recovery) at 15-18 hours after surgery compared to the combined administration of both dexmedetomidine and ketamine. Furthermore, there was no significant effect of intraoperative doses of dexmedetomidine and ketamine on postoperative EEG evolution. The results do not address if these EEG improvements are associated with lasting effects on neurodevelopmental outcomes, but the work of the authors adds valuable insight into the potential neuroprotective roles anesthetics can have in neonatal CHD surgery.

Title: Reduced Single Platelet Force is Associated with Increased Transfusion Volume in Neonatal Cardiopulmonary Bypass Surgery

Authors: Oshinowo O*, Copeland R, Lam WA, Myers DR, Downey L (Emory University)

Description: Neonates are at risk for bleeding and massive transfusions after cardiopulmonary bypass (CPB). Little is known about the effect of CPB on platelet function in the newborn. When platelet contraction forces decrease there is disruption of mechanical clotting resulting in increased blood loss. Therefore, in this preliminary study, the authors sought to identify whether impaired platelet contraction forces are associated with post-bypass coagulopathy in neonates. They performed Platelet Contraction Cytometry (PCC), a quantitative test of platelet function, in three neonates undergoing repair on CPB.

The authors showed in two patients the platelet contraction forces decreased after bypass and transfusion. In the patient with the greater drop, there was an increased blood transfusion requirement suggesting that transfusion needs may increase when there is a greater drop in platelet force. They also showed the transfusion of donor adult platelets after bypass restored the loss of highly contractile platelets, reflecting a restoration of hemostasis. This preliminary study provides a possible insight into the importance of mechanical clot properties of platelets in hemostasis and that PCC may provide both a quantitative measure of severity of coagulopathy and guidance for transfusion in neonates after CPB.

Title: Patient-Specific Computational Fluid Dynamic Simulations of the Norwood Procedure

Authors: Kaplan M*, Barker P, Hill K, Chen J, Chamberlain, Randles A (Duke University)

Description: The Norwood procedure for hypoplastic left heart syndrome (HLHS) may be associated with insufficient coronary perfusion and elevated pulmonary vascular resistance (PVR). Previous 3D computational fluid dynamic (CFD) studies have explored the effect of the Norwood shunt diameter on coronary perfusion, but none have used realistic patient-specific anatomies or have studied the effects of the shunt type on coronary perfusion. The authors of this study performed patient-specific CFD simulations from routine clinical data to determine if the choice of Norwood shunt type and diameter quantitatively changes coronary perfusion and/or pulmonary sheer stress. To accomplish this, they used catheter-based angiography and Doppler echocardiography to generate 3D anatomic reconstructions, which then allowed them to stimulate models of flow within the aorta, pulmonary arteries, and coronary arteries.

Contrary to some hypothesis, their models for a modified Blalock-Taussig Shunt (mBTS) did not demonstrate a significant decrease in coronary perfusion compared to those with a right ventricle to pulmonary artery shunt (RVPAS). This was likely because the diastolic run-off associated with a mBTS was offset by increased early diastolic inflow from a higher aortic pressure. Nonetheless, they showed that with smaller shunt sizes there is a decrease in the coronary perfusion for both a mBTS and RVPAS. Finally, they used the models to show that the RVPAS maximizes shear stress metrics, whereas a mBTS minimizes shear stress metrics, and a valved RVPAS results in intermediate values. Therefore, based on their findings they suggest the optimal shunt type to generate beneficial pulmonary artery stresses requires knowledge of patient-specific considerations rather than a one-shunt-type-fits-all surgical strategy.

The work by this group provides insight on how the type of shunt used in the Norwood procedure effects coronary perfusion and pulmonary artery shear stress and, therefore, potentially help reduce the mortality and morbidity associated with the procedure.

Title: Ex Vivo Effect of Fibrinogen Concentrate on the Fibrin Network Structure in Neonates after Cardiopulmonary Bypass

Authors: Nellenbach K, Downey L*, Brown A, Guzzetta N (Emory University)

Description: Neonates have an increased risk of bleeding after bypass due to an immature coagulation system and acquired hypofibrinogenemia. Deficiency of fibrinogen likely contributes to substantial bleeding after CPB. Cryoprecipitate administration is the current standard of care for hypofibrinogenemia in the United States. However, fibrinogen concentrate (FC; RiaSTAP®, CSL Behring, Marburg, Germany) is an alternative. It is a purified form of fibrinogen derived from adult plasma, but there is limited experience in both its use for open-heart surgery and in pediatrics. Therefore, the authors sought to characterize the effect of standard transfusion with cryoprecipitate versus FC on clot properties in neonates undergoing cardiac surgery.

They collected blood samples from ten neonates at three time periods: baseline, immediately after discontinuation of CPB, and after transfusion of cryoprecipitate and platelets. The samples were then centrifuged to yield platelet-poor plasma, on which ex vivo clot formation studies were performed. In addition, FC was added to the post-CPB samples for analysis as well. Using confocal and scanning electron microscopy, fibrin clot structure was analyzed. They showed the samples obtained immediately after CPB had the lowest fibrin density. In addition, the administration of a clinical dose of FC increased the fibrin density to a greater degree than that observed with the in vivo post-transfusion blood samples. While FC administration may assist in forming denser clots – thus promoting better post-CPB hemostasis -- further analysis to examine strength and degradation kinetics will be needed to assess risk of thrombotic events.

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