Background: Clinical observations suggest that pulmonary artery occlusion pressure (PAOP) underestimates the resuscitative volumes required prior to release of aortic cross-clamp.
Methods: To investigate pressure-volume relationships associated with repair of abdominal aortic aneurysm (AAA), we simultaneously monitored PAOP by pulmonary artery catheter (PAC) and estimated left ventricular (LV) diastolic volume using two-dimensional transesophageal echocardiography (TEE) in 22 patients undergoing AAA repair. Data from PAC monitoring and TEE were collected before, during, and after aortic occlusion. TEE cross-sectional images were obtained at the mid-papillary level.
Results: Overall, PAOP correlated with left ventricular end-diastolic area (LVEDA), but the correlation was not particularly strong (r = 0.37, P < 0.0001). Even within individual patients, LVEDA varied widely for a given PAOP. The strength of the correlation between PAOP and LVEDA also appeared to deteriorate during the course of surgery. The best correlation was seen prior to aortic cross-clamping (r = 0.50, P < 0.0001), but fell somewhat during aortic cross-clamping (r = 0.41, P < 0.0001), and even further after unclamping (r = 0.25, P = 0.005).
Conclusion: This study demonstrates a relatively weak correlation between PAOP and LVEDA using intraoperative TEE during AAA repair. Furthermore, the strength of the correlation worsened during surgery, particularly after unclamping. Although unclear at this time, this finding may be attributable to changes in LV compliance. We found TEE to be a valuable adjunct in guiding volume resuscitation of patients undergoing AAA repair.