Changes in cardiac output during major vascular surgery.

The largest decrease in cardiac output in patients undergoing aortoiliac bypass grafting for peripheral arterial occlusive disease occurs when the aorta is cross-clamped, not when it is declamped. This decrease was reduced in four patients who received 2 liters of Ringer's lactate preoperatively. Postoperatively, as peripheral resistance decreases, a large volume of fluid may be necessary to maintain homeostasis. By knowing when changes in cardiac hemodynamics can be expected to occur during aortoiliac surgery, it may be possible to prevent cardiac complications.