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ABSTRACT. Extracorporeal membrane oxygenation (ECMO) is frequently used for treatment of patients with severe hypoxemia due to lifethreatening respiratory failure. Due to this hypoxemia, the myocardium of these patients is insufficiently provided with oxygen, and consequently their cardiac function commonly deteriorates. But veno-arterial (V-A) ECMO provides oxygenated blood to the coronary arteries from ECMO circuit insufficiently. To increase the coronary blood flow distributed from ECMO, we placed the arterial cannula 1 cm above the aortic valve and evaluated the regional blood flow from the proximal arterial cannula in comparison with the distal cannula. Eight neonatal dogs weighting 1.8-2.5 kg were supported by V-A ECMO. The regional blood flow from the arterial cannula was measured by injection of colored microspheres into ECMO circuit. The site of the arterial cannula was changed under fluoroscopy. The bypass flow was maintained at either 50 or 100 ml/min/kg. We found that the coronary blood flow distributed from the proximal arterial cannula was significantly higher than that from the distal cannula. The proximal arterial cannula appears necessary to provide sufficient oxygenated blood to the coronary circulation during V-A ECMO. Therefore, it is expected that the increased cardiac function may improved, and that the survival rate of the patients with retarded cardiac function due to severe hypoxemia may increase by proximal placement of the arterial cannula during V-A ECMO. MATERIALS AND METHODSAnimal: Eight mongrel neonatal dogs within 1 month old were used in this study. Their body weight ranged between 1.8 to 2.5 kg. The animals were subjected to the experiment, after checking their fitness clinically by preoperative examination, including physical examination, clinical laboratory evaluation, and radiography of the thorax. The experiment was carried out in accordance with the Guide for Animal Experimentation, Faculty of Agriculture, Kagoshima University.Surgical procedure: The dogs fasted for 24 hr before surgery. The animals were anesthetized with 25 mg/kg of pentobarbital sodium intravenously, and intubated with a cuffed endotracheal tube, and ventilated mechanically throughout the experiment. The peak air pressure was set at 12 mmHg, and the respiratory rate was set between 8 and 15 times per minute. Topical 1% lidocain was used as necessary to dilate the vessel and to insert the cannula easily. An incision was made in the neck of each dog, and either a 6F or 7F cannula was inserted into the left jugular vein in a caudal direction until the tip of the cannula was placed in the right atrium. A 6F polyvinyl cannula was inserted into the left femoral vein in a cranial direction until the tip was placed in the vena cava. These two cannulae placed in the jugular and femoral vein were used for withdrawal blood during ECMO. These venous cannulae were connected to each other by a Y-shape connector. Either a 6F or 7F cannula was inserted into the left carotid artery until the tip of the cannula was 3-4 cm...

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