Preoperative fasting can evoke a hypovolemia which may cause a hemodynamic instability during introduction of anesthesia.

The purpose of this study is to test the hypothesis that a defined preoperative volume substitution compared to standard procedure will result in a reduced incidence of hemodynamic instabilities during introduction of anesthesia in elective surgery patients.

The preoperative fasting period often lasts longer than 2 hours as recommended by various national and international anesthetic guidelines. Thus, hypovolemia is more often then anticipated. In awake patients this condition is often masked. Introduction of anesthesia often leads to an unmasking of hypovolemia with a consecutive hemodynamic instability.

Aim of the study is to test the hypothesis that a preoperative volume substitution (8 ml/kg RingerAcetate Solution in 15 min. prior to introduction of anesthesia) reduces possible hemodynamic instabilities during initiation of anesthesia.

Inclusion Criteria:

• Age ≥ 18 years
• thyreoid, parathyroid or gallbladder surgery
• general anesthesia

Exclusion Criteria:

• coronary artery disease
• congestive heart disease (≥ New York Heart Association (NYHA) 2)
• insulin dependent diabetes mellitus
• renal insufficiency (creatinine > 2,0 mg/dl)
• cerebrovascular disease
• severe hypertension (≥ antihypertensive drugs)