Physiologic Aspects of Porcine Hemorrhage. III. Heart Rate and Arterial Blood Pressure Changes during Spontaneous Recovery from 30 and 50 Percent Blood Volume Loss in the Conscious Animal.

Young domestic swine, 6 animals per group, were subjected to 30 and 50 hemorrhage of their estimated blood volume over a 1-hour period while in a conscious recumbent state. Before and for 5 hours after hemorrhage, hemodynamic functions were measured to assess the characteristics of spontaneous recovery from hemorrhagic hypotension. Six additional pigs, treated similarly except for hemorrhage, served as controls. Immediately after 30 hemorrhage, arterial mean, systolic, and diastolic blood pressure were 79, 104, and 59 mm Hg, respectively. During th 5-hour recovery period, these pressures reverted to 105, 129, and 81 mm Hg which were nearly the same as pre-hemorrhage values. Heart rates were unaltered by hemorrhage but increased slightly during recovery. Pulse pressure was not significantly affected by hemorrhage or recovery, while hematocrits declined during and following blood loss. After 50 hemorrhage, arterial mean, systolic, and diastolic pressures were 46, 79, and 26 mm Hg, respectively. During the recovery period these pressures rose to 81, 104, and 62 mm Hg all of these values remained significantly below pre-hemorrhage values. Pulse pressure increased significantly during the recovery period, while hematocrits decreased to an even greater degree than those in the 30 group. In both hemorrhage groups spontaneous recovery was associated with a progressive decrease in hematocrit which reflected a transfer of interstitial fluid to the circulation.