ABSTRACT
The mammalian cardiovascular system is small relative to body weight, with sharp response to stresses placed on the patient. Tissue O2 delivery must be balanced with tissue oxygen (O2) demand at any moment in time. The sequence of “protective” actions begins when regional blood flow and O2 delivery are mismatched and do not meet the immediate metabolic needs of the tissues. Hemorrhage or hypovolemia results in decreased circulating fluid volume producing decreased blood pressure parameters. Shock is a symptomatic syndrome that is diagnosed by recognizing clinical signs reflecting regional perfusion maldistribution. Immediate resuscitation is indicated in cases demonstrating clinical signs of shock. All resuscitation strategies are based on improving O2 transport and delivery to tissues. Mortality in hypovolemic shock is directly related to duration of the ischemic insult. Crystalloid fluids are mixtures of sodium chloride and other physiologically active solutes. Hypertonic saline produces rapid hemodynamic improvement following acute administration. Colloids are large-molecular-weight substances that do not readily pass across capillary walls.
