Goal Directed and Liberal Fluid Therapy

Intraoperative fluid management for major abdominal and intestinal surgeries is quite important in terms of postoperative organ perfusion and complications. Many complications such as acute renal failure, hypotension, arrhythmia, and anastomosis leak may occur secondary to intraoperative hypovolemia whereas hypervolemia may cause pulmonary edema, postoperative pneumonia, prolonged mechanical ventilation, delayed wound healing, edema in the gastrointestinal system (GIS), and decreased GIS motility.

In the perioperative period, fluid therapy and gastrointestinal function may complement each other or complicate it. If fluid therapy is not optimal, it may cause delayed gastrointestinal function and avoid early oral intake. If gastrointestinal dysfunction develops in the perioperative period, it may lead to fluid and electrolyte loss and metabolic problems. Thus, the intraoperative fluid management of the patient is very important.

Accurate assessment of a patient's volume status is an important goal for the anesthetist in the operating theatre to achieve hemodynamic stability and adequate tissue oxygenation. Different intraoperative fluid management protocols are in use for this purpose. The most common one is conventional fluid management (CFM). Fluid replacement is managed according to clinical assessment and heart rate (HR), arterial blood pressure (ABP) and central venous pressure (CVP) monitorization.

While goal-directed fluid therapy (GDFT) is a perioperative strategy, where fluid administration targets continuously-measured hemodynamic variables, such as cardiac output, stroke volume, stroke volume variation, pulse pressure variation and other factors to guide intravenous and inotropic therapy, with the aim of maximizing tissue perfusion and oxygen delivery.

Cardiac output is assessed by static indices or dynamic indices. Static indices of cardiac preload such as central venous pressure (CVP) and pulmonary artery wedge pressure are of little help for decisions regarding volume replacement. Dynamic variables such as pulse pressure variation (PPV) and stroke volume variation (SVV) are increasingly used to detect the cyclic fluctuation of the arterial pressure wave in the mechanically ventilated patient in order to predict fluid responsiveness.

Direct measurement of SV using noninvasive techniques has become an accepted tool for stroke volume optimization and guiding fluid administration in highly risk surgical patients. Many technologies are used to measure stroke volume, including Doppler monitoring, bio impedance/reactance measurements, and arterial waveform analysis. So, when stroke volume optimization is used as the end point, it could improve the outcomes for surgical patients with good prediction of fluid administration.

Impedance cardiography (ICG) is an accurate technique for noninvasive determination of hemodynamic variables such as stroke volume (SV), stroke volume index (SVI), cardiac output (COP), cardiac index (CI), systemic vascular resistance (SVR), and systolic time ratio (STR). ICG use electrical impedance changes to generate waveform that depend on volume and velocity of blood injected into aorta as well as the force and rate of left ventricle contraction. From that curve beside heart rate and blood pressure, stroke volume ,COP ,SVR and other hemodynamic parameter are derived