Autonomic response to hypovolemic shock

Hypovolemic shock resulting from hemorrhage is a leading cause of death following traumatic injuries in the United States. The autonomic nervous system plays a significant role in providing physiological compensation during severe blood loss in an effort to maintain adequate delivery of oxygen (DO2) to vital organs in the face of falling cardiac output and oxygen carrying capacity. In this chapter, we detail the integration of various autonomically mediated compensatory mechanisms that are activated from the initiation of hemorrhage and serve to maintain adequate vital organ perfusion and hemodynamic stability in the scenario of reduced systemic DO2. We then describe the dynamics of autonomic failure that leads to the onset of decompensated shock. Data are introduced that challenge legacy concepts related to autonomic mechanisms that underlie baroreflex functions.