Hypoxémies sévère en cours de CEC : démarches diagnostiques et conduite à tenir

Abstract

The occurring of hypoxemia during CPB is a potentially serious event that requests emergency correction. Hypoxemia can be documented by repeated arterial blood gases, either systematic, or performed because of a dark red coloration of arterial blood or a drop in venous oxygen saturation, pulse oximetry or near infrared spectroscopy. The continuous surveillance of PaO 2, if available, will provide the earliest diagnosis. Except hypoxemia due to operating troubles (low flow on a canulation problem, acute haemorrhage, insufficient anaesthesia, etc.), hypoxemia during CPB is linked either to a defect in the administering of gases at the oxygenator, or to a deficient oxygenator. The analysis of the fraction of oxygen at the oxygenator exit (FeoO 2) will prove the defect in the administering of gases. The treatment consists in the use of a spare oxygen cylinder in case of hospital supply failure, the use of the accessory anaesthesia circuit in case of a flaw in the flow meter, or the identification and repair of leaks. In case of a deficient oxygenator, the measure of resistances will differentiate an obstruction associated to a shunt (caused by a lack in anticoagulation, or by platelet activation phenomenon, whether transitional or not) from a loss in the membrane transfer properties, which will most often request a replacement of the oxygenator.