• Sublingual microcirculation [ Time Frame: 24 hour ] [ Designated as safety issue: No ]
  

• Gases, hemoglobin and oxygen saturations [ Time Frame: 24 hours ] [ Designated as safety issue: No ]
  
• Electrolytes and lactate [ Time Frame: 24 hours ] [ Designated as safety issue: No ]
  
• Anion gap corrected to albumin [ Time Frame: 24 hours ] [ Designated as safety issue: No ]
  

Shock is the failure of circulatory system to maintain adequate cellular perfusion. Septic shock is primarily a form of distributive shock and is characterized by ineffective tissue oxygen delivery and extraction associated with inappropriate peripheral vasodilation despite preserved or increased cardiac output. In sepsis, a complex interaction between pathologic vasodilation, relative and absolute hypovolemia, myocardial dysfunction, and altered blood flow distribution occurs due to the inflammatory response to infection. Even after the restoration of intravascular volume, microcirculatory abnormalities may persist and lead to maldistribution of cardiac output. Notwithstanding the complexity of its pathophysiology and treatment, to maintain adequate organ perfusion is a main goal in the management of severe sepsis and septic shock. For this purpose, optimization of intravascular volume and preload is the more important step. Fluid challenge is a term used to describe the initial volume expansion period in which the response of the patient to fluid administration is carefully evaluated. During this process, large amounts of fluids may be administered over a short period of time under close monitoring to evaluate the patient's response and avoid the development of pulmonary edema. Fluid challenge should be given in all patients suspected of hypovolemia. Fluid resuscitation may consist of natural or artificial colloids or crystalloids. There is no evidence-based support for one type of fluid over another. As the volume of distribution is much larger for crystalloids than for colloids, resuscitation with crystalloids requires more fluid to achieve the same end points and might result in more edema. In addition, post-hoc analysis and experimental studies suggest that colloids might be superior to crystalloids, in terms of physiologic end-points, recruitment of the microcirculation and mortality.