Comparison of Cardiorespiratory Changes in Surviving and Nonsurviving Shock Dogs

Hemodynamic measurements in experimental hemorrhagic shock have been widely studied in the past.^1-6 Most of the reported studies were conducted on an acute hemorrhagic shock preparation similar to that described by Wiggers.¹ These studies consistently described decreased cardiac output (CO) and increased peripheral resistance, which began shortly after the onset of hemorrhage. On replacement of the shed blood, CO transiently returned toward, but usually did not reach, control values. Then CO declined again, and most of the animals died within about six hours.¹ The acute hemorrhagic shock preparations such as Wiggers' technique have been used to provide a standardized experimental shock preparation to study physiological alterations. However, the types of hemorrhage and shock found in the clinical situations were variegated. Hemorrhage usually occurred less abruptly, and the hypovolemic state may have been more prolonged. Moreover, except for the early period immediately after the onset of hemorrhage, the