Perioperative Fluid Management in Patients Receiving Major Abdominal Surgery - Effects of Normal Saline Versus an Acetate Buffered Balanced Infusion Solution on the Necessity of Catecholamines for Cardiocirculatory Support

Background Intraoperative hypotension is a common problem that significantly contributes to perioperative mortality and morbidity. At the moment the "gold standard" for perioperative fluid management is the so called "goal-directed therapy" that features fluid resuscitation followed if necessary catecholamines if needed for perioperative cardiocirculatory support.

Worldwide the so called "physiological" sodium chlorid (0.9% NaCl) solution is the most often used infusate for perioperative fluid management. Despite its widespread use physiological saline has its major disadvantages such as the increased incidence of metabolic acidosis. Nevertheless catecholamines have their significant side effects as well (eg diminished renal perfusion, increased cardiovascular morbidity) and they therefore should be used with caution.

In a prior study by group members on patients undergoing renal transplantation receiving either physiological saline or an acetate-buffered infusate showed a 50% decrease in catecholamine necessity in the acetate-buffered infusate group. The investigators therefore would like to evaluate the effects of the perioperative fluid choice on the necessity of catecholamine use.

Aim

* Evaluation of the perioperative fluid choice on the necessity of catecholamines for cardiocirculatory support.
* Description of the relationship between perioperative fluid choice and minimal blood pressure as well as the time to catecholamine use and their dosage.

Methods The investigators plan a prospective randomized-controlled trial of all patients undergoing major abdominal surgery at the Vienna General Hospital and Medical University of Vienna. Fluid management and catecholamine use will be based on a oesophageal Doppler -based treatment scheme.


Eligibility Criteria:
Inclusion Criteria:

* All patients scheduled for open elective major abdominal surgery and expected to last a minimum of 2 hours will be included in the study.

(Major abdominal surgery includes all gynecological, urological and general surgical operations requiring laparotomy)

Exclusion Criteria:

* Patients younger than 18 years of age
* Patients unable to give informed consent
* Pregnancy or breastfeeding
* Patients transferred form the intensive care unit to the operating theater
* Patients with an already established catecholamine therapy
* Emergency operation
* Chronic inflammatory diseases (chronic inflammatory rheumatoid diseases, chronic inflammatory renal diseases, chronic inflammatory infectious diseases, chronic inflammatory bowel diseases, chronic liver disease with signs of liver insufficiency)
* Severe cardiovascular disease (heart disease with an ejection fraction below 30%, instable coronary syndromes, severe valvular disease)
* Any signs of infection or sepsis
* Any contraindication for oesophageal Doppler monitoring (oesophageal and aortic pathology, planned oesophageal resection)
* Renal insufficiency with a glomerular filtration rate below 30ml/min
* Patients with additional epidural anesthesia are excluded from the study if epidural anesthesia is planned to be used for analgesia intraoperatively