Single hemorrhage: a clinically relevant canine model of hemorrhagic shock

Clinically encountered hemorrhagic shock is usually caused by a single, rapid hemorrhage secondary to trauma. Experimental models of shock, however, have utilized anesthetic agents and hemorrhage protocols which may compromise the clinical relevance of their findings. This report characterizes the response of conscious, splenectomized dogs to a single hemorrhage of varying rates and volumes, uncomplicated by the presence of anesthetic agents. The duration of a 40 ml kg-1 hemorrhage affected the magnitude of blood pressure recovery, but did not alter the decompensating drop in blood pressure. The shortest hemorrhage duration was chosen for further study, as the blood pressure profile for this hemorrhage duration demonstrated most clearly the recovery, plateau, and decompensation phases. Increasing the hemorrhage volume to 43 ml kg-1 caused a reproducible decrease in the magnitude of the blood pressure recovery, the time to decompensation, and the time to death. Splenectomized dogs, then, demonstrate a reproducible response to a fixed-volume hemorrhage, making chronically instrumented conscious dogs a good animal model with which to study the progression of hypovolemic shock.