The first group will be patients who present to the SICU and are hemodynamically unstable. Hemodynamic instability will be defined as systolic blood pressure less than 90 mmHg or the requirement of continuous infusion of vasopressors to maintain the systolic blood pressure over 90 mmHg. The second group of patients will be a similar group that is expected to require massive fluid or blood resuscitation (>6L crystalloid or >6 units of blood) to maintain systolic blood pressure over 90 mmHg. This second group of patients will consist mainly of trauma patients. These patients or their closest available relative will be approached for consent to participate in the trial. For patients enrolled through a surrogate who regain their decision making capacity they will be informed of their participation in the study by one of the investigators.