The Type of Aortic Cannula and Membrane Oxygenator Affect the Pulsatile Waveform Morphology Produced by a Neonate-Infant Cardiopulmonary Bypass System In Vivo *Akif U ¨ ndar, †Andrew J. Lodge, †Casey W. Daggett, *‡Thomas M. Runge, †Ross M. Ungerleider, and *John H. Calhoon *Division of Thoracic Surgery, Department of Surgery, The University of Texas Health Science Center, San Antonio, Texas; †Division of Thoracic Surgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina; and ‡Biomedical Engineering Program, College of Engineering, The University of Texas at Austin, Austin Texas, U.S.A. Abstract: Although the debate still continues over the ef- fectiveness of pulsatile versus nonpulsatile perfusion, it has been clearly proven that there are several significant physi- ological benefits of pulsatile perfusion during cardiopul- monary bypass (CPB) compared to nonpulsatile perfusion. However, the components of the extracorporeal circuit have not been fully investigated regarding the quality of the pulsatility. In addition, most of these results have been gathered from adult patients, not from neonates and in- fants. We have designed and tested a neonate-infant pul- satile CPB system using 2 different types of 10 Fr aortic cannulas and membrane oxygenators in 3 kg piglets to evaluate the effects of these components on the pulsatile waveform produced by the system. In terms of the meth- ods, Group 1 (Capiox 308 hollow-fiber membrane oxygen- ator and DLP aortic cannula with a very short 10 Fr tip [n  2]) was subjected to a 2 h period of normothermic pul- satile CPB with a pump flow rate of 150 ml/kg/min. Data were obtained at 5, 30, 60, 90, and 120 min of CPB. In Group 2 (Capiox 308 hollow-fiber membrane oxygenator and Elecath aortic cannula with a very long 10 Fr tip [n  7]) and Group 3 (Cobe VPCML Plus flat sheet membrane oxygenator and DLP aortic cannula with a very short 10 Fr tip [n  7]), the subjects’ nasopharyngeal temperatures were reduced to 18°C followed by 1 h of deep hypothermic circulatory arrest (DHCA) and then 40 min rewarming. Data were obtained during normothermic CPB in the pre- and post-DHCA periods. The criteria of pulsatility evalu- ations were based upon pulse pressure (between 30 and 40 mm Hg), aortic dp/dt (greater than 1000 mm Hg/s), and ejection time (less than 250 ms). The results showed that Group 1 produced flow which was significantly more pul- satile than that of the other 2 groups. Although the same oxygenator was used for Group 2, the quality of the pul- satile flow decreased when using a different aortic cannula. Group 3 did not meet any of the criteria for physiologic pulsatility. In conclusion these data suggest that in addi- tion to a pulsatile pump, the aortic cannula and the mem- brane oxygenator must be chosen carefully to achieve physiologic pulsatile flow during CPB. Key Words: Aor- tic cannula—Membrane oxygenator—Pulsatile perfu- sion—Cardiopulmonary bypass—Extracorporeal circula- tion—Neonates and Infants. During cardiopulmonary bypass (CPB), neonates and infants are more often subjected to extreme con- ditions such as deep hypothermia, profound hemo- dilution, and circulatory arrest than adults. Accord- ing to a 1994 survey, 50% of the centers performing pediatric heart surgery use deep hypothermic circu- latory arrest (DHCA) for complex cases if the pa- tient is less than 1 month old (1). Currently, 1 out of 4 neonates and infants undergoing CPB with or with- out DHCA suffers some degree of temporary or per- manent brain injury (2–4). Although controversy still exists, pulsatile perfusion has been shown to have several beneficial effects over nonpulsatile perfusion during CPB (5–14). Murkin et al. (6) showed that the use of pulsatile perfusion contributed to the signifi- cantly lower mortality and morbidity that was ob- served when compared to nonpulsatile perfusion in 316 clinical cases. However, most of these results were gathered from adults, not from neonates and Received July 1997; revised January 1998. Presented in part at the XIth World Congress of the Interna- tional Society for Artificial Organs, held June 29–July 1, 1997, in Providence, Rhode Island, U.S.A. Address correspondence and reprint requests to Dr. Akif U ¨ n- dar, Texas Children’s Hospital, Congenital Heart Surgery, 6621 Fannin St. MC 1-2285, Houston, TX 77030-2399, U.S.A. Artificial Organs 22(8):681–686, Blackwell Science, Inc. © 1998 International Society for Artificial Organs 681