Lung impairment following cardiac surgery in patients with pulmonary hypertension

Postoperative respiratory management following cardiac surgery is sometimes troublesome in patients with pulmonary hypertension. We retrospectively studied the relationship between the etiology of preoperative pulmonary hypertension and the postoperative decline of blood oxygenation capacity by focusing on the postoperative intravascular fluid volume.

Sixteen adult patients with an atrial septal defect (preload group) and 17 patients with solitary mitral valve disease (afterload group) were studied. The mean age of the patients in the preload and afterload group was 51 and 52 years old, respectively.

Preoperative pulmonary-systemic pressure ratio and pulmonary artery resistance index were significantly higher in the preload group than in the afterload group. The respiratory index (RI) and the pulmonary shunt ratio (Qs/Qt) measured immediately after the operation was larger in the afterload group than in the preload group. Postoperative RI and Qs/Qt remained high until postoperative day 3 in both groups. In the preload group RI on postoperative day 1 had a reverse correlation with the central venous pressure (CVP). Meanwhile, the RI in the afterload group on postoperative day 1 was slightly larger in patients with a high CVP and pulmonary capillary wedged pressure. Similar relationships were seen in the relations between pulmonary capillary wedged pressure and RI in the afterload group. CONCLUSIONS In conclusion, a preoperative pulmonary vascular change and a postoperative precipitous decrease of pulmonary blood flow may have caused postoperative lung oxygenation impairment in the preload group. An extended period of extracorporeal circulation associated with cardiac arrest and postoperative volume overload may have caused lung impairment in the afterload group. In aspect of postoperative management, low CVP is beneficial to the patients in the afterload group, however, hypovolemia should be avoided in patients of the preload group.