The purpose of this study is to determine if there is equivalence between two different methods of treating patients with severe bloodstream infection called sepsis. We will randomly assign patients to one of two treatment methods. One of the treatment methods is the current standard of care and uses an infrared sensor on the end of a catheter to determine the adequacy of treatment. The second treatment method is identical to the first but instead of the infrared sensor a blood test that is performed as a part of standard care (with blood drawn from the catheter) will be used to determine the adequacy of treatment. This study will attempt to determine an easier method of guiding treatment.

Inclusion Criteria:

1. Suspected infection
2. Any two of four criteria of systemic inflammatory response
3. SBP < 90 mm Hg after 20cc/kg crystalloid (septic shock) or either a whole blood lactate > 4 mmol/L (severe sepsis).

Exclusion Criteria:

1. Age < 18 years
2. Pregnancy
3. Established "Do Not Resuscitate" orders prior to enrollment
4. Primary diagnosis other than sepsis
5. Requirement for immediate surgery in < 6 hours from admission
6. Any absolute contraindication to central venous catheterization