Confounding factors in the hemorrhage of conscious swine: a retrospective study of physical restraint, splenectomy, and hyperthermia.

A retrospective study showed that variability in the responses of heart rate and mean arterial pressure to hemorrhage in conscious swine can be induced by handling procedures, hyperthermia, and splenectomy. All animals were hemorrhaged 38.5 ml/kg over 1 hour. Physical restraint caused tachycardia prior to hemorrhage, an effect that was enhanced during hemorrhage; hemorrhage had no effect on the heart rate of unrestrained animals. Animals restrained in a sling also had an attenuated fall in mean arterial pressures throughout the experiment compared to normothermic swine. Splenectomized swine had elevated heart rates compared to sham-operated animals, with the difference persisting throughout hemorrhage. No difference in mean arterial pressure was noted due to splenectomy. These sources (handling, hyperthermia, and splenectomy) of experimental variability should be considered in the design and interpretation of experiments using conscious swine.