• combined perioperative morbidity [ Time Frame: within length of stay in hospital ]
  

• Tissue oxygenation, Wound Infection, Incidence of postoperative nausea and vomiting (PONV) and pain [ Time Frame: within length of stay in hospital ]
  

For a long time there is a raging debate whether crystalloid solutions or colloid solutions are better suited for fluid therapy. Early proponents both for crystalloids [Shires 1961] and colloids [Shoemaker 1979] deserve credit for elucidating important facts about volume replacement therapy - without answering the primary question. Elaborate reviews comparing crystalloid and colloid therapy for critically ill patients have been performed in the late nineties and updated recently [Roberts 2004]. However, it has been suggested that both questions and answers of reviews leave us none but wiser [Webb 1999]. Although a plethora of studies comparing crystalloid vs. colloid therapy in the last decades have been published, volume replacement therapy is still considered to be based on dogma and personal beliefs [Boldt 2003].

Goal-directed intraoperative fluid therapy monitored by Esophageal Doppler identifies volume-responders, thereby decreasing length of stay in hospital in orthopedic [Sinclair 1997], cardiac [Mythen 1995], and abdominal surgery patients [Gan 2002, Wakeling 2005, Noblett 2006]. However, all these studies have been performed with a colloid to be the substance applied. Thus, it has been questioned whether monitoring with the Esophageal Doppler monitor, or the application of additional colloid improved outcome [Horowitz, Kumar 2003].

Consequently, we will use Esophageal Doppler Monitoring for intraoperative goal-directed fluid therapy to compare the effects of crystalloid vs. colloid therapy on various organ systems, assessing combined perioperative morbidity [Bennett-Guerrero 1999] .