ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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Comparative Study
Coupling pediatric ventricle assist devices to the Fontan circulation: simulations with a lumped-parameter model.
In pediatric ventricular assist device (VAD) design, the process of matching device characteristics and dimensions to the relevant disease conditions poses a formidable challenge because the disease spectrum is more highly varied than for adult applications. One example arises with single-ventricle congenital defects, which demand palliative surgeries that create elevated systemic venous pressure and altered pulmonary hemodynamics. Substituting a mechanical pump as a right ventricle has long been proposed to eliminate the associated early and postoperative anomalies. ⋯ Pulsatile operation mode with rotational speed regulation highlighted the importance of TCPC and pulmonary artery compliances. Four different pumps and three patient-specific anatomical TCPC pathologies were studied. Magnitudes of the equivalent TCPC resistances were found to be comparable to the vascular resistances of the normal baseline circulation, significantly affecting both the VAD design and hemodynamics.
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Case Reports
Duration of cardiopulmonary resuscitation before extracorporeal rescue: how long is not long enough?
Despite the extensive resources required, extracorporeal cardiopulmonary resuscitation (ECPR) has been recognized as an extension of traditional CPR. The reported duration of CPR before ECPR initiation is similar between survivors and nonsurvivors, but the duration of CPR that results in futility of care is unknown. We report two cases of prolonged CPR followed by ECPR resulting in acceptable neurologic outcomes. ⋯ The Extracorporeal Life Support Organization registry is a plausible forum to collect data regarding ECPR. We suggest that possible predictive variables be collected. Until then, practitioners must rely on experience and judgment regarding the value of ECPR in children.
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Comparative Study
Precise quantification of pulsatility is a necessity for direct comparisons of six different pediatric heart-lung machines in a neonatal CPB model.
Generation of pulsatile flow depends on an energy gradient. Surplus hemodynamic energy (SHE) is the extra hemodynamic energy generated by a pulsatile device when the adequate pulsatility is achieved. The objective of this study was to precisely quantify and compare pressure-flow waveforms in terms of surplus hemodynamic energy levels of six different pediatric heart-lung machines in a neonatal piglet model during cardiopulmonary bypass (CPB) procedures with deep hypothermic circulatory arrest (DHCA). ⋯ The PPP produced the greatest surplus hemodynamic energy. Most of the pediatric pulsatile pumps (except Mast-PR) generated significant surplus hemodynamic energy. None of the nonpulsatile roller pumps generated adequate surplus hemodynamic energy.
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We report a simplified modification of the cardiopulmonary bypass (CPB) circuit to create a closed extracorporeal membrane oxygenation (ECMO) circuit for short-term cardiac support. From November 2001 to December 2004, a specially designed CPB circuit was indicated for 25 patients in whom the need of ECMO was expected. A bypass containing a nonprimed ECMO bladder was inserted in the venous line, bypassing the cardiotomy reservoir. ⋯ Common complications were bleeding requiring reexploration (four patients), brain injury (three patients), oxygenator failure (three patients), and sepsis (one patient). Converting an open CPB circuit to a closed ECMO circuit is viable with adequate results. The advantages are less exposure to blood products, hemodynamic stability, and cost reduction.
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The Department of Health and Human Services, at the direction of Congress, has recently begun to address concerns regarding the development of medical devices designed specifically for the pediatric population, including devices for pediatric mechanical circulatory support, as evidenced by the National Institutes of Health's (NIH) funding of several development contracts. Food and Drug Administration (FDA) approval for marketing of these devices will typically follow either of two regulatory pathways: the Humanitarian Device Exemption (HDE) or the Premarket Application (PMA). An HDE is limited both in the extent of clinical use and economic benefit to the manufacturer, but does not require data derived from a clinical trial for market approval. ⋯ In addition, an HDE requires a demonstration of probable benefit, whereas a PMA requires a demonstration of a reasonable assurance of effectiveness. The evidence that can be used to support an HDE or a PMA approval may include both preclinical and clinical data. Types of preclinical tests needed depend upon the device design and its intended use, because circulatory support devices are all unique.