Recent Advances in Pediatric Cardiopulmonary Bypass.

There have been numerous recent advances geared specifically toward the practice of pediatric cardiopulmonary bypass (CPB). These advances include the development of the first oxygenator intended solely for the neonatal CPB patient; pediatric oxygenators with low prime volumes and surface areas, which allow flows up to 2 L/min; pediatric oxygenators with integrated arterial filters; and miniature ultrafiltration (UF) devices, which allow for high rates of ultrafiltrate removal. When used in combination with heart lung machines with mast-mounted pumps, these advances can result in significant decreases in CPB circuit surface areas and prime volumes. This may attenuate CPB-associated hemodilution and decrease or eliminate the need for homologous red blood cells during or after CPB. In addition to these equipment-related advances, changes in myocardial protection strategies and the technique of modified UF as it relates to these advances are discussed.

Cryoprecipitate and platelet administration during modified ultrafiltration in children less than 10 kg undergoing cardiac surgery.

UNLABELLED: The timing of blood product administration after cardiopulmonary bypass (CPB) may influence the amount of postoperative transfusion and chest tube output. We performed a retrospective study of a novel technique of administering blood products during modified ultrafiltration (MUF) in congenital cardiac surgery. A Control Group (CG; n = 55) received cryoprecipitate and platelets after modified ultrafiltration. The Treatment Group (TG; n = 59) received cryoprecipitate and platelets during MUF. Volumes of blood products transfused in the operating room, initial coagulation parameters in the cardiac intensive care unit, and first 24-hour chest tube output were recorded. Age (116 +/- 198 versus 84 +/- 91 days), weight (4.6 +/- 1.8 versus 4.5 +/- 1.4 kg), duration of bypass (121 +/- 50 versus 139 +/- 57 minutes), and Aristotle scoring (9.3 +/- 2.7 versus 9.1 +/- 3.1) were not significantly different when comparing the control and treatment groups, respectively. Intraoperative packed red blood cells (74.4 +/- 34.8 versus 79.3 +/- 58.0 mL/kg, p = .710), fresh-frozen plasma (58.3 +/- 27.1 versus 59.1 +/- 27.2 mL/kg, p = .849), cryoprecipitate (7.3 +/- 5.1 versus 8.6 +/- 5.9 mL/kg, p = .109), and platelet (19.0 +/- 14.6 versus 23.7 +/- 20.8 mL/kg, p = .176) administration were the same in the control and treatment groups, respectively. However, fibrinogen levels on arrival in the coronary intensive care unit were significantly higher (305 +/- 80 versus 255 +/- 40 mg/dL, p < .001) in the CG compared with the TG. Twenty-four-hour chest tube output was not significantly different but the CG (17.76 +/- 9.34 mL/kg/24 hours) was trending lower than the TG (19.52 +/- 10.94 mL/kg/24 hours, p = .357). In an attempt to minimize CPB-associated bleeding and transfusions, we changed our practice by adjusting the timing of blood product administration after patient separation from CPB. The goals of the change in practice were not measurably different in terms of shorter intraoperative times, fewer blood transfusions, or less chest tube output at our institution. KEYWORDS: congenital heart disease, modified ultrafiltration, cryoprecipitate, platelets, cardiopulmonary bypass.

International pediatric perfusion practice: 2011 survey results.

New cardiopulmonary bypass devices and new innovative methods are frequently reported in the literature; however, the actual extent to which they are adopted into clinical practice is not well known. We distributed an electronic survey to 289 domestic and international pediatric congenital surgery centers in an effort to measure attributes of current clinical practice. The survey consisted of 107 questions relating to program demographics, equipment, and techniques. Responses were received from 146 (51%) of queried centers and were stratified into five distinct geographic regions (North America, Central and South America, Oceana, Europe, and Asia). Most of the responding centers reported use of hard shell venous reservoirs. Closed venous systems were used at 50% of reporting centers in Central and South America as compared with only 3% in North America and 10% in Asia. Seventy-one percent of the programs used some form of modified ultrafiltration. Use of an arterial bubble detection system varied between 50% use (Central and South America) vs. 100% (North America and Oceana). "Del Nido" cardioplegia is more common in North America (32%) than any other continent, whereas Custodial HTK solution is much more prevalent in Europe (31%). Wide variation in practice was evident across geographic regions, suggesting opportunities for further investigation and improvement.

Neonatal extracorporeal membrane oxygenation devices, techniques and team roles: 2011 survey results of the United States' Extracorporeal Life Support Organization centers.

In early 2011, surveys of active Extracorporeal Life Support Organization (ELSO) centers within the United States were conducted by electronic mail regarding neonatal Extracorporeal Membrane Oxygenation (ECMO) equipment and professional staff. Seventy-four of 111 (67%) U.S. centers listed in the ELSO directory as neonatal centers responded to the survey. Of the responding centers, 53% routinely used roller pumps for neonatal ECMO, 15% reported using centrifugal pumps and 32% reported using a combination of both. Of the centers using centrifugal pumps, 51% reported that they do not use a compliance bladder in the circuit. The majority (95%) of roller pump users reported using a compliance bladder and 97% reported using Tygon" S-97-E tubing in the raceway of their ECMO circuits. Silicone membrane oxygenators were reportedly used by 25% of the respondents, 5% reported using micro-porous hollow fiber oxygenators (MPHF), 70% reported using polymethylpentene (PMP) hollow fiber oxygenators and 5% reported using a combination of the different types. Some form of in-line blood monitoring was used by 88% of the responding centers and 63% of responding centers reported using a circuit surface coating. Anticoagulation monitoring via the activated clotting time (ACT) was reported by 100% of the reporting centers. The use of extracorporeal cardiopulmonary resuscitation (ECPR) was reported by 53% of the responding centers with 82% of those centers using a crystalloid primed circuit to initiate ECPR. A cooling protocol was used by 77% of the centers which have an ECPR program. When these data are compared with surveys from 2002 and 2008 it shows that the use of silicone membrane oxygenators continues to decline, the use of centrifugal pumps continues to increase and ECMO personnel continues to be comprised of multidisciplinary groups of dedicated allied health care professionals.

Retrospective analysis comparing hollow fiber and silicone membrane oxygenators for neonates on ECMO.

There is little information showing the use of microporous polypropylene hollow fiber oxygenators during extra-corporeal life support (ECLS). Recent surveys have shown increasing use of these hollow fibers amongst ECLS centers in the United States. We performed a retrospective analysis comparing the Terumo BabyRx hollow fiber oxygenator to the Medtronic 800 silicone membrane oxygenator on 14 neonatal patients on extracorporeal membrane oxygenation (ECMO). The aim of this study was to investigate the similarities and differences when comparing pressure drops, prime volumes, oxygenator endurance, and gas transfer capabilities between the two groups.

Cardiopulmonary bypass using argatroban as an anticoagulant for a 6.0-kg pediatric patient.

A patient was born with transposition of the great arteries, double-outlet right ventricle, interrupted aortic arch, and a ventricular septal defect and underwent a Damus-Kaye-Stansel procedure with a modified Blalock-Taussig shunt at 14 days old. Three months later, this patient presented with hypoxia and bradycardia was found to have a thrombus present in the main pulmonary artery extending to right pulmonary artery. After initiation of thrombolytic therapy, the patient became severely hypoxic and required the institution of extracorporeal membrane oxygenation. As the result of unknown heparin resistance independent of adequate antithrombin III levels, argatroban therapy was used to achieve desired anticoagulation. The patient was taken to the operating room and converted to conventional cardiopulmonary bypass once adequate activated clotting times were achieved using argatroban. This case report summarizes the use of argatroban as an anticoagulant for a 6.0-kg pediatric patient undergoing cardiopulmonary bypass.

Argatroban usage for anticoagulation for ECMO on a post-cardiac patient with heparin-induced thrombocytopenia.

We report a post-Norwood Stage I patient requiring ECMO support using Argatroban as an anticoagulant following diagnosis of heparin-induced thrombocytopenia (HIT). A 2.6 kg female was born with hypoplastic left heart syndrome and underwent a Norwood Stage I operation on day 4 of life. The patient weaned off cardiopulmonary bypass with no complications and was routinely placed on a ventricular assist device (VAD) for 3 days. Heparin was infused at a rate of 16-32 IU/ kg/h to maintain an ACT of 160-180 seconds. Two days after VAD termination, the patient was placed on continuous veno-veno hemofiltration (CVVH). Shortly after CVVH, the patient was diagnosed with HIT and placed on an Argatroban infusion. Five days later, a VAD and subsequent ECMO was used because of decreasing left ventricular function, gross body edema, and poor renal function. This case report summarizes the use of Argatroban during VAD and ECMO support for a patient diagnosed with HIT.

Routine mechanical ventricular assist following the Norwood procedure--improved neurologic outcome and excellent hospital survival.

BACKGROUND: Although excellent survival following the Norwood procedure for palliation of hypoplastic left heart syndrome (HLHS) is being achieved by some, most centers, especially the ones with small surgical volume and limited experience, continue to struggle with initial results. Survivors often showed evidence of significant neurologic injury. The early postoperative care is labor-intensive as attempts are made to balance the systemic and pulmonary circulation for these infants. We report our experience with routine use of mechanical circulatory assist to support the increased cardiac output requirements present following Norwood procedure. METHODS: Eighteen consecutive infants undergoing Norwood operation for HLHS (Oregon Health & Science University [OHSU] 13; University of Louisville [UL] 5) were placed on a ventricular assist device (VAD) immediately following modified ultrafiltration in the operating room using the cardiopulmonary bypass (CPB) cannulas that were in the right atrium and the neoaorta. VAD flows were maintained at approximately 200 mL x kg(-1) x min(-1) and the patients were transported to the intensive care unit (ICU). Patients operated at OHSU also received neurodevelopmental testing before their Glenn procedure, approximately 4 to 6 months following their Norwood operation. RESULTS: All patients were stable on VAD support and no attempt was made to balance the systemic and pulmonary circulation. The ventilator was manipulated to achieve systemic Pa0(2) between 30 and 45 mm Hg and PaC0(2) between 35 and 45 mm Hg. Evidence of hypoperfusion (increasing lactates) was managed by increasing the VAD flow. Lactates normalized [< 2 mmol/L]) by 1.8 +/- 1.1 days following surgery. Average time of VAD support was 3.1 +/- 1.0 (range, 2 to 5 days) and average time until chest closure was 3.4 +/- 1.5 (range, 2 to 8 days). There were two cases of postoperative bleeding (11.1%) requiring reexploration and one case of mediastinitis (5.5%) in a patient who has now gone on to successful Glenn. Sixteen of the eighteen patients survived (hospital survival mean 89% with a 95% confidence interval of 63.9% to 98.1%; 12/13 OHSU [92.3%]; 4/5 UL [80%]). Neurodevelopmental testing using the Mullen Scales of Early Learning and the Vineland Adaptive Behavior Scale were normal for all infants tested. CONCLUSIONS: Routine postoperative use of VAD can support the increased cardiac output demands of infants following Norwood operation and results in a stable postoperative convalescence that does not require aggressive ventilator or inotrope manipulation. Although not a panacea, this strategy can simplify postoperative management, lead to excellent hospital survival, and possibly augment cerebral oxygen delivery, resulting in improved neurologic outcomes for this challenging group of patients.

Quantification of the effect of altering hematocrit and temperature on blood viscosity.

Rheological changes occurring with the conduct of cardiopulmonary bypass affect the distribution of blood throughout the cardiovascular system. The purpose of this study was to evaluate the effects of changing physical characteristics of fluid on the dynamics of blood flow in an in vitro model. An extracorporeal model simulating coronary vessel constriction was designed that consisted of tubing with varying internal diameters. Tubing sizes were selected as percentage reductions (11, 33, 56, and 78%) of a normal sized (3.6 mm) coronary artery. Flow rates were randomly varied between 150 and 300 mL min(-1) temperatures of 6 and 37 degrees C, and hematocrits of 0, 20, and 38%. Endpoints included viscosity, pressure drop, and volume distribution. As temperature fell from 37 to 6 degrees C, viscosity increased with hematocrit as follows: 192% at 0%, 225% at 20%, and 249% at 38%, p < .001. Pressure drop increased significantly across each tubing size ranging from 173-351%, p < .01, as fluid was cooled from 37 to 6 degrees C. However, intraconduit statistical differences in volumetric distribution of flow were not achieved. Although the induced hypothermia resulted in increases in resistance, statistical significance was only seen in the smallest lumen conduit. In conclusion, the effects of changing temperature has profound influence on fluid distribution secondary to changing blood viscosity in an in vitro model for fluid distribution. Knowledge of such flow alterations may aid in determining optimal perfusion strategies where vessel constrictions are encountered.