Objective: In patients with functional single ventricular physiology, the avoidance of cardiopulmonary bypass offers many advantages including earlier extubation, decreased necessity of inotropic support, improved hemodynamical status and reduced likehood of postoperative prolonged pleural effusion. We believe that the bidirectional cavopulmonary anastomosis operations may be performed with transient external shunt techniques. The purpose of this prospective study is the peri- and post-operative comparison of different transient external shunt methods used in bidirectional cavopulmonary shunt operations. Methods: Between years 1997 and 2000, 30 patients have undergone bidirectional cavo-pulmonary shunt operation by using three different types of external shunt. The mean patient age was 13 months (range, 3 months-3 years). Previous operations had been performed in ten patients (33%). All patients were divided into three groups according to type of external shunt used. In group A (ten patients), the transient external shunt was constructed between superior vena cava and right atrium by uniting two standard venous cannulas with a Y-connector. In group B (ten patients), the external shunt was performed with a single short venous cannula constructed between superior vena cava and right atrium. In group C (ten patients), the external shunt was constructed between superior vena cava and left pulmonary artery by using a single short venous carmula. During operation, central venous pressure (CVP), arterial O-2 saturation and mean arterial blood pressure were recorded continuously. Results: All operations are completed without the establishment of cardiopulmonary bypass. Hospital mortality was 3.3%. One patient in group A died because of low cardiac output at the end of postoperative day 2. All patients were extubated within 4 h. In groups A-C mean superior vena caval pressures were measured 28, 24 and 21 mmHg, respectively during superior vena cava-right pulmonary artery anastomosis. In both groups A and B patients, arterial O-2 saturation decreased to a minimum 53 +/- 2 and 53 +/- 2%, respectively during the operation. In the group C, minimum arterial O-2 saturation was measured 82 2%. Although mean arterial pressure decreased in all groups during clampage; in group C patients, this drop is not significant. Conclusion: Based on the study presented here, bidirectional cavo-pulmonary anastomosis can be carried out by using different types of transient external shunt. The best hemodynamical condition and arterial O-2 levels were achieved with the shunt constructed between superior vena cava and left pulmonary artery. (C) 2003 Elsevier Science B.V. All rights reserved.