Stroke Volume Variation Versus Central Venous Pressure Guidance for Reducing Perioperative Blood Loss During Open Liver Resection

Liver resection is a major surgery that can be associated with significant intraoperative blood loss and blood transfusion. Among high-volume centers, median intraoperative blood loss ranges between 300-800 ml. Excessive blood loss is a strong independent predictor of worsened postoperative outcomes, increasing morbidity and mortality rates by 20%-35%. Additionally, perioperative allogeneic blood transfusions are associated with deleterious outcomes, including tumor recurrence and increased rates of complications and death. The liver is a highly vascular organ with minimal vascular resistance, receiving up to 25% of cardiac output and pooling 20% of the splanchnic blood. Hepatic veins are a common source of venous hemorrhage. The pressure in the hepatic veins is directly correlated with the pressure in the vena cava and reducing cardiac preload results in decreased hepatic vein congestion. Therefore, low central venous pressure anesthesia (typically below 5 mmHg) can reduce the pressure gradient for retrograde venous bleeding, facilitate the outflow of blood from hepatic veins, and decrease blood volume and pressure in the liver. This anesthetic method is the standard technique to minimize blood loss during liver resection. Central venous pressure was the static parameter used to indicate the right ventricular end-diastolic volume index (RVEDI) and was believed to be correlated with volume status. Despite this, central venous pressure did not reliably predict preload responsiveness due to the curvilinear shape of the ventricular pressure-volume curve, which indicates a poor relationship between ventricular filling pressure and volume. Additionally, the placement of a central venous catheter could lead to serious complications such as arterial cannulation, pneumothorax, and infection. Arterial waveform analysis is dynamic hemodynamic monitoring based on the interaction between the heart and lungs in patients with mechanical ventilation. Stroke volume variation (SVV) is one aspect of arterial pressure waveform analysis and is a less invasive alternative technique for guiding preload status and fluid management in patients undergoing major abdominal surgery. In liver resection, several anesthetic methods are used to achieve low central venous pressure (CVP \< 5 mmHg) during the liver parenchymal dissection phase. These methods include intraoperative volume restriction, administration of venodilators or vasodilators, the use of forced diuresis with furosemide, and the implementation of hypovolemic phlebotomy. As mentioned, central venous pressure is a static hemodynamic monitoring parameter and poorly correlates with volume status. Recently, stroke volume variation has been recognized as a good parameter to predict volume status and fluid responsiveness in patients undergoing liver resection. However, no previous publications have studied the efficacy of stroke volume variation monitoring compared with central venous pressure monitoring to reduce perioperative blood loss during open liver resection. The study aimed to compare the efficacy of maintaining high stroke volume variation versus low central venous pressure in reducing perioperative blood loss during the liver transection phase in open liver resection.