This is the pathophysiologic tale of two young domestic pigs, both barrows, which served as experimental subjects in a study of hemorrhagic hypotension. One week prior to the study a chronic carotid catheter was surgically implanted in each animal and exited from the dorsal surface of the neck. On the day of study each animal was brought into the laboratory in a small, 2 foot by 4 foot, mobile cage and was provided with bedding material. After 15 minutes or so of chewing, rooting, grunting and bedding rearrangement they voluntarily assumed a recumbent position at which point the carotid catheter was connected to a 3-way stopcock and appropriate pressure tubing, transducers, etc., for the removal of blood and the measurement of functional variables. After 30 additional minutes of unrestrained, recumbent rest two sets of baseline measurements were made at 15 minute intervals. Then 60 percent of the estimated blood volume was removed over a one-hour period; blood loss was based, arbitrarily, on an exponential scale such that 10 percent increments of the total blood volume were removed uniformly over successive intervals of about 7, 7.5, 8.5, 10, 12, and 15 minutes. The various functional measurements were repeated immediately after hemorrhage, at 15 minute intervals during the first two hours of spontaneous recovery and both pigs became nauseous and vomited during the course of hemorrhage. In both instances these effects were observed when slightly over 40 percent of the estimated blood volume had been removed. For the most part, both pigs displayed similar physiological and biochemical characteristics immediately after hemorrhage. Subsequently, however, the functional changes associated with spontaneous recovery differed markedly in the two animals. One pig, number 54, survived and appeared reasonable healthy 24 hours after hemorrhage. The other, number 35, showed early signs of recovery but ultimately deteriorated and died at two hours and 50 minutes into the recovery period.
The data collected from these animals are depicted in Figures 1 through 23. Some of the pathophysiologic questions raised by these data are listed immediately thereafter.