Dose-response Study of Arginine Supplementation in Severe Sepsis

Inclusion Criteria: * Written informed consent from close relative * Age \> 18 years * Patient meets the general criteria for severe sepsis or septic shock, diagnosed less than 48 h prior to study inclusion (see appendix A; in Dutch). * Patient must be relatively hemodynamically stable, defined as stable blood pressure (variation in mean arterial pressure \<15 mm Hg) during 2 h without necessity of increasing the vasopressor dose, inotropic support or rate of fluid administration. * Systemic and pulmonary arterial catheters in place with continuous pressure monitoring. * Patients in whom the clinician is prepared to provide full life support during the duration of the study, including a life expectance of \> 24 h. Exclusion Criteria: * Shock due to any cause other than sepsis (e.g. drug reaction or drug overdose, pulmonary embolus, burn injury etc.) * Corticosteroid use (prolonged intake of \> 1mg/kg daily or intake of \> 70 mg/day for 7 consecutive days within 1 month preceding the study) * Liver cirrhosis * Chronic pancreatitis * Diabetes mellitus type I * Metastases, haematological malignancies or chemotherapy * Patients on dialysis (CVVH or other)