Spectral Analysis of Central Venous Pressure Waveform

The right internal jugular vein is located at the first rib level under ultrasound-guidance. Using an out-of-plane technique, a needle is introduced into the lumen of the vessel. The aspiration of blood into the syringe connected to the hub of the needle confirms the placement of the needle tip in the lumen. After the syringe is detached from the needle, a guidewire is advanced into the vessel lumen through the needle. A dilator is introduced over the guidewire and subsequently is removed. Then, a central venous catheter is introduced over the guidewire into the vessel lumen through the pathway expanded by the dilator. The catheter tip is placed in the superior vena cava by inserting the catheter as far as the distance between the edge of the right transverse process of the first thoracic vertebra and the carina, which is preoperatively measured on a posteroanterior chest radiograph.

Following the placement of a central venous catheter, a fluid-filled system for monitoring central venous pressure is connected to the proximal lumen of the catheter. The reference transducer is placed at the level of 4/5 of the anteroposterior diameter of the thorax.

Patients fast from 10 pm the day before surgery. On the arrival at the operating room, an intravenous catheter for Plasmalyte infusion is placed into the right cephalic or basilic vein. The distal lumen of the central venous catheter is used for the infusion of 6% hydroxyethyl starch. Fluid requirements due to anesthesia, surgery, and no per os intake are not replaced by minimizing the administration of the fluids. Five minutes after the collection of the baseline data, 20 mg of furosemide is administered to promote diuresis for facilitating the venous outflow of the liver. An additional dose of furosemide 20 mg is given if the urine output is \<1 ml/kg within 30 minutes after the first dose. Unless the second dose of furosemide produces \>1 ml/kg of urine within 30 minutes, 40 mg of furosemide is administered. In the absence of effective diuresis (1 ml/kg within 30 minutes after each dose), the use of furosemide is abandoned and the patients are excluded from the study.

Immediately after the graft procurement, 500 ml of 6% hydroxyethyl starch are infused over 25 minutes. Afterward, Plasmalyte is infused at a rate of 10 ml/min until the end of surgery.

Following anesthesia induction, the right radial artery is catheterized. The catheter is connected to the EV1000 monitor (Edwards Lifesciences, Irvine, CA) through the FloTrac transducer (Edwards Lifesciences). The transducer is level with the one for central venous pressure monitoring. Using pulse contour analysis without external calibration, the stroke volume for each heartbeat is measured. At a 20-second interval, stroke volume variation is calculated as (maximum stroke volume - minimum stroke volume)/mean stroke volume.