A case of shunting postoperative patent foramen ovale under mechanical ventilation controlled by different ventilator settings

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Claudio Pragliola *
Sara Di Michele
Domenico Galzerano
(*) Corresponding Author:
Claudio Pragliola | claudio.pragliola@libero.it

Abstract

A 56-year old male with ischemic heart disease and an unremarkable preoperative echocardiogram underwent surgical coronary revascularization. An intraoperative post pump trans-esophageal echocardiogram (TOE) performed while the patient was being ventilated at a positive end expiratory pressure (PEEP) of 8 cm H2O demonstrated a right to left interatrial shunt across a patent foramen ovale (PFO). Whereas oxygen saturation was normal, a reduction of the PEEP to 3 cm H2O led to the complete resolution of the shunt with no change in arterial blood gases. Attempts to increase the PEEP level above 3 mmHg resulted in recurrence of the interatrial shunt. The remaining of the TEE was unremarkable. Mechanical ventilation, particularly with PEEP, causes an increase in intrathoracic pressure. The resulting rise in right atrial pressure, mostly during inspiration, may unveil and pop open an unrecognized PFO, thus provoking a right to left shunt across a seemingly intact interatrial septum. This phenomenon increases the risk of paradoxical embolism and can lead to hypoxemia. The immediate management would be to adjust the ventilatory settings to a lower PEEP level. A routine search for a PFO should be performed in ventilated patients who undergo a TEE.

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Author Biographies

Claudio Pragliola, The Heart Centre, King Faisal Specialist Hospital and Research Centre, Ryadh

Heart Centre

Domenico Galzerano, The Heart Centre, King Faisal Specialist Hospital and Research Centre, Ryadh

Heart Centre