Case Report A potential propensity for failure secondary to clot embolism in neonatal ECMO Espeed Khoshbin, David Machin, Hilliary Killer, Giles J Peek, Andrzej W Sosnowski and Richard K Firmin Division of Cardiac Surgery, University of Leicester /Heart Link ECMO Centre , Glenfield Hospital , Leicester , UK Objective : To report a single case of oxygenator failure caused by clot embolism originating from the bladder; and to discuss some preventative options. Case report :A 2.5 kg neonate with a diagnosis of influenza A received veno-arterial (V  /A) extracorporeal membrane oxygena- tion (ECMO) for cardiorespiratory support. Halfway through treatment, she underwent an elective circuit change for numerous clots in her circuit. The patient continued to consume vast quantities of platelets and developed a fatal oxygenator failure after 18 days. Discussion : Amongst the factors influencing the outcome in events of a sudden unexpected oxygenator failure are the severity of patient illness, the size of the clot relative to the size of the oxygenator, the availability of a previously primed circuit and the ease and speed of priming a new oxygenator. Conclusion : There is a need for improvement in the design of small oxygenators and ECMO circuits. Adjustment of the coagulation para- meters and lowering the tolerance towards clots in the circuit by electively changing them may reduce the incidence of sudden unexpected oxygenator failure. However, using a slightly larger Medos oxygenator may gain valuable time needed to arrange an oxygenator/ circuit change. Perfusion (2005) 20, 177 /181. Introduction Medos Hilite (Medos Medizintechnik, Frankfurt, Germany) oxygenators have improved gas exchange efficiency and reduced transfusion requirements in adult extracorporeal membrane oxygenation (ECMO). 1,2 In neonates, they provide adequate gas exchange and offer technical advantages, in terms of more efficient priming, reduced haemodynamic resistance and better control and preservation of coagulation proteins, than Medtronic (Medtronic, Minneapolis, MN, USA) oxygenators. 3 Currently, all ECMO centres in the UK have adapted to using Medos oxygenators. The material / polymethyl pentene (PMP) / properties and the structural design of these oxygenators has made them more compact, with a smaller surface area and lower priming volumes compared to Medtronic (Silicon) oxygenators [surface area of 0.31 versus 0.8 (m 2 ) and priming volume 55 versus 100 (mL), respectively, as measured by the manufacturers]. In March 2001, our institution began using Medos Hilite 7000LT oxyge- nators for adult ECMO instead of Medtronic 1-4500- 2A. In September 2001, their use was extended to neonates by using Medos Hilite 800LT to replace Medtronic 0800. Today, this type of oxygenator is used for patients of all age groups. However, con- cerns were raised about the tolerance of the smaller oxygenator against clots. Case report A neonate, weighing 2.5 kg, with a corrected gesta- tional age of three weeks had been treated with antibiotics and ventilatory support for pneumonia and respiratory arrest. The patient was referred for ECMO with an oxygen saturation of 60%, PaO 2 of 33 mmHg on 100% oxygen and a PaCO 2 of 60 mmHg on high frequency oscillatory ventilation (HFOV) and nitric oxide at 20 parts per million. Chest X-rays showed evidence of severe bilateral pneumonia with total consolidation of both lungs. She had to be hand bagged during transfer and was immediately cannulated to veno-venous (VV)- ECMO through an Origin double-lumen cannula (12 French) placed into the right internal jugular vein by semi-Seldinger technique and oxygenated using a Medos Hilite 800LT oxygenator. 4 Contrary to our usual experience, where inotropic requirements fall after the start of ECMO, her requirements escalated within the first 24 hours and became acidotic, requiring renal support. Echo- cardiogram revealed a dilated, poorly functioning right ventricle and pulmonary arteries. There was Address for correspondence: Espeed Khoshbin, Division of Cardiac Surgery, University Hospitals of Leicester NHS Trust, ECMO Office, Groby Road, Leicester, LE3 9QP, UK. E-mail: khoshbinuk@yahoo.co.uk Perfusion 2005; 20: 177 /181 # 2005 Edward Arnold (Publishers) Ltd 10.1191/0267659105pf798cs