A comparison of survival at different degrees of hemorrhagic shock in germ-free and germ-bearing rats.

We have previously reported superior survival after one level of hemorrhagic shock in germ-free (GF) rats compared with germ-bearing (GB) rats. The objective of this study was to determine the effect of the GF state on survival at different degrees of hemorrhagic shock. GF and GB rats were bled to a mean arterial blood pressure of 30 mmHg. Shock was terminated after 10, 20, 40, or 80% of the maximum shed blood volume was reabsorbed spontaneously. Both shock time and time to decompensation were significantly longer in GF rats (p < .05). Comparative survival was greater for GF rats at most levels of shock (p < .01). This superiority in survival was greatest at moderate shock levels and decreased at severe shock levels. There may be several reasons for the increased tolerance of GF animals to hemorrhagic shock such as metabolic or immunologic variations. It is hard to avoid the fact, however, that the most notable difference between the GF and GB rat is the presence or absence of bacteria.