Hemodynamic instrumentation and design

The central venous pressure (CVP) was monitored continuously with a three-lumen central venous catheter placed using ultrasound-guided right internal jugular vein puncture and arterial pressure was monitored invasively in both groups using a catheter placed in the radial artery. The mean arterial blood pressure (MAP), HR, cardiac index (CI), stroke volume index (SVI), stroke volume variation (SVV), and left ventricular contractility index, which is the maximum increase in the speed of intraventricular pressure (dp/dt_max), were continuously monitored through PRAM (Most Care monitoring system; Vytech Healthcare, Padova, Italy) via a pressure catheter (Pulsion Medical Systems, Munich, Germany) in the CO-G group.

Hemodynamic management included fluid transfusion and use of vasopressors and/or inotropes: (1) Fluid management protocol: In the control group, fluid management was implemented mainly according to CVP, urine volume, bleeding, etc. CVP was maintained at a level of 6-12 mmHg, and the urine volume at ≥ 20 mL/h. If the urine volume was < 20 mL/h and/or CVP < 6 mmHg, 4% albumin or crystalloid was infused to expand the volume; if the urine volume was < 20 mL/h and/or CVP > 12 mmHg, 0.5 g/kg furosemide was also administered to decrease fluid load. In the CO-G group, fluid was infused at a rate of 10 mL/kg/h to maintain SVV at 12%-15%. If SVV was > 12%, 4% albumin or crystalloid was administered in combination with CI, SVI, and other parameters; and (2) Vasopressor and/or inotrope protocol: In the control group, if MAP was < 50 mmHg, norepinephrine or dopamine was pumped intravenously, and if MAP fell rapidly below 30 mmHg after the opening of the portal vein, rehydration and/or epinephrine of 1-5 mg/kg was administrated. In the CO-G group, the administration of vasopressors and/or inotropes according to the CO and other hemodynamic parameters is illustrated in the PRAM diagram (Figure ​(Figure1).1). Other management: Albumin and blood products were infused to maintain the blood volume and hemoglobin level at ≥ 8 g/L. The electrolyte and acid-base balance were maintained within the normal range during surgery and were kept warm.

Pressure recording analytical method. CI: Cardiac index; MAP: Mean arterial blood pressure; SVI: Stroke volume index; SVV: Stroke volume variation.