Cristalloid versus colloid in patients with severe sepsis and septic shock

INTERVENTION: Subjects are assigned to be resuscitated either with cristalloids (sodium chloride 0.9%) or cristalloid combined with colloids (polyhydroxyethylstarch 10%) until resuscitation endpoints have been established. Endpoints are an intrathoracal blood volume of >850 ml/m^2, a mean arterial pressure of >70 mmHg and a cardiac index of >3.0 l/min/m^2. CONDITION: Sepsis, Septic shock ; Infections and Infestations ; Septicemia PRIMARY OUTCOME: The relation between the resuscitation regime and the tissue oxygen tension.; Furthermore the relation between the resuscitation regime and the amount of extravascular lung water, as well as the relation between the amount of extravascular lung water and the tissue oxygen tension. SECONDARY OUTCOME: 1. Subcutaneous temperature; 2. Laboratory findings: hemoglobin, hematrocrite, albumin, arterial and venous blood gasses; 3. Hemodynamic parameters: cardiac output, VO2, DO2; 4. Respiratory parameters: PEEP, PaO2/FiO2 ratio; inotropes INCLUSION CRITERIA: Sever sepsis or septic shock (according to the criteria of the American College of Chest Physicians/Society of Critical Care Medicine) in a mechanically ventilated ICU patient.