• G Papadopoulos, M Brock, and K Eyrich.
• Klinik für Anaesthesiologie und operative Intensivmedizin, Universitätsklinikum Benjamin Franklin der FU Berlin.
• Anaesthesist. 1996 Mar 1; 45 (3): 235-9.

UnlabelledIntraoperative paradoxical air embolism may occur even if a patent foramen ovale (PFO) is excluded by contrast transoesophageal echocardiography (TEE) under 20 cm H2O positive airway pressure. It is questionable whether the combination of PEEP and ventilation with a large tidal volume increases the sensitivity of contrast TEE in detecting a PFO.MethodsEighty healthy patients (ASA status I, II) scheduled for surgery in the supine position and ranging from 25 to 72 years of age were investigated by TEE, which was performed in the biatrial viewing mode (short axis). Echocardiographic contrast (10 ml agitated gelatine solution) was injected during two different ventilation manoeuvres. Manoeuvre I: Contrast injection during the application of 20 cm H2O positive airway pressure for 5 s. The pressure was released when the right atrium became completely opacified by echo targets. The injected bolus was observed throughout the ventilatory cycle, with special attention being given to early expiration and systole. A right-to-left shunt was assumed if five echo targets were observed in the left atrium. Manoeuvre II: Contrast injection during ventilation with PEEP (15 cm H2O), a tidal volume of 1,200 ml, and a respiratory rate of 6/min.ResultsThe frequency of a PFO causing a right-to-left interatrial shunt was 8.7% (7 cases) in manoeuvre I and 15% (12 cases) in manoeuvre II. In one case a PFO was diagnosed intraoperatively by chance.DiscussionThe use of provocation manoeuvres including ventilation with PEEP and high tidal volumes might improve the ability to detect a PFO presenting with right-to-left interatrial shunt by intraoperative contrast TEE, but does not have 100% sensitivity. However, our results clearly indicate that ventilation with PEEP and high tidal volumes may predispose to paradoxical embolism.

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