An evaluation of the end points of resuscitation.

It is 2:00 A.M. and, as the general surgeon on trauma call at your medium-sized community hospital, you have just completed operative repair of a bulletshattered liver in a 20-year-old youth, your city’s most recent victim of gang violence. After rapidly completing your Joint Commission for the Accreditation of Healthcare Organizations-mandated operative dictation, you perform your first postoperative check of the patient in the intensive care unit. Obtunded and pale, the patient now lies in an ICU bed before you. His condition is poor: his blood pressure is low, pulse rapid and thready, urine output nonexistent. You resuscitate with intravenous saline and blood, and improvement is seen, but results seem suboptimal. How will you know you are giving this young man his best chance at survival, that your resuscitation is sufficient and complete? Resuscitation is the act of restoring full life to those approaching death; for purposes of this discussion, this entails treatments directed toward resolution of shock.The capricious syndrome “shock” takes many forms, but its recognition and treatment involve a commonality in approach. Three basic questions require answer: (1) Is the patient in shock? (2) How does one treat this form of shock? and (3) When is treatment for shock sufficient? Although diagnosis of and primary treatment approach to different forms of shock can be problematic, this discussion shall concentrate on the last question: the adequacy of resuscitation. Every clinician who cares for sick patients must know how to recognize and treat shock. Just as important is the knowledge of optimal goal(s) to reach with such treatment; such goals are often referred to as end points of resuscitation. Included in this article is a discussion of various measures that have been proposed and tested as end points to resuscitation, such as blood pressure, cardiac output, mixed venous oxygen saturation, blood lactate, base deficit, oxygen delivery and consumption, gastric mucosal pH, tissue oxygen tension, and venous hypercarbia. Why is it important that a patient in shock be fully resuscitated? Numerous published studies have shown that underresuscitated shock leads, if not to immediate death, to Systemic Inflammatory Response Syndrome, eventual irreversible body-wide ischemia, and then Multiple Organ Dysfunction Syndrome with its attendant high mortality (Fig. 1). Although discussion of the molecular mechanisms for Systemic Inflammatory Response Syndrome is beyond the scope of this review, the same studies support such contributing hypotheses as ischemiareperfusion injury, macrophage-induced cytokine and neutrophil activation, and a state of continuing systemic hypoperfusion that progresses to ischemic cellular injury and cell death. Adequate resuscitation implies adequate systemic perfusion, meaning sufficient oxygen delivery to meet the cell’s metabolic needs, correct cellular ischemia, and restore the cell’s energy stores. Without adequate oxygen delivery (DO2), the organism accumulates an ever-increasing oxygen “debt” (Figs. 2–3). This oxygen debt, expressed as the cumulative difference between measured oxygen consumption at baseline and during shock, at some point becomes unrecoverable. The opinions and assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.