7.6.2 Left cavities purge

Before the heart resumes mechanical perfusion activity, it is essential to clear the left cavities (pulmonary veins, left atrium, left ventricle, root of the aorta) of any air bubbles that may have accumulated during the opening of these cavities or during cavitation and thermal variations. The air will accumulate in the overhanging areas: pulmonary veins, especially the right ones, the top of the interatrial septum, the mitro-aortic angle in the LA, the apical part of the interventricular septum (especially during Trendelenburg), the right sinus of Valsalva. Transoesophageal echocardiography is very useful in locating residual air pockets and assessing their size (see Figure 7.44) [1].

There are several techniques available to "debulk" the heart chambers.

• ForcedTrendelenburg position (prevention of cerebral emboli);
• Continuous suction (100-500 mL/min) through the cardioplegia cannula into the aortic root, held in place until after weaning;
• Brake on venous return from the ECC to fill the right chambers;
• Sustained pulmonary hyperinflation (inspiratory pressure of 30 cm H₂ O) to fill the LA through the pulmonary veins;
• Drainage by direct needle puncture of the cavity;
• Heart shaking and manipulation;
• Right roll (favours LA-LV passage), left roll (favours LV-aorta passage);
• Inotropic stimulation and high perfusion pressure (≥ 80 mmHg);
• Return to ECC in extreme cases.

Air that becomes trapped in the siphon of the pulmonary veins is only expelled when pulmonary venous flow becomes sufficient, i.e. during weaning. Systemic gas embolism manifests itself primarily as ischaemia (ST elevation) in the territory of the right coronary or venous bypass grafts re-implanted into the aorta, because these vessels terminate at the anterior part of the ascending aorta in a supine patient. If debulking is insufficient, air may embolise when the patient is transferred to bed because of the unavoidable body movements in several directions.

© CHASSOT PG, GRONCHI F, April 2008, last update, December 2019

 Reference

1. TINGLEFF J, JOYCE FS, PETTERSON G. Intraoperative echocardiography study of air embolism during cardiac operations. Ann Thorac Surg 1995; 60:673-7