BACKGROUND: Transesophageal echocardiography (TEE) is now a common part of intraoperative monitoring in cardiac surgery. Complications related to TEE have not been frequently reported, yet there have been some cases of hemodynamic compromise and interference with ventilation. We measured the changes of hemodynamic and ventilatory variables in associated with the insertion of TEE probe in pediatric cardic pateints. METHODS: Twenty six patients (age = 11.0 +/- 5.1 months) weighing under 10 kg who scheduled for elective operations for congenital heart disease were studied prospectively. We measured heart rate, mean arterial pressure, central venous pressure, peak inspiratory pressure, end-tidal carbon dioxide pressure, pulse oxygen saturation and arterial blood gases. The variables were measured before and after each TEE probe insertion. RESULTS: No significant changes in hemodynamic variables were noted after TEE probe insertion. Arterial carbon dioxide pressure increased significantly after TEE probe insertion. Peak inspiratory pressure increased markedly in three infants who weighed under 7 kg, which showed no statistical significance over all. In one patient, the endotracheal tube was extubated accidentally, and reintubated after reinstitution of partial cardiopulmonary bypass. CONCLUSIONS: TEE is noninvasive monitoring and complications thereof are rare, but vigilance against hemodynamic and ventilatory compromise is highly needed especially for small infants. In addition the possibility of extubation should be kept in mind and should be detected early.