Microcirculatory changes in visceral organs during slowly progressing hypovolaemia in pigs

The loss of 30% of the blood volume, reported in early experimental haemorrhagic pancreatitis, was simulated in anaesthetized piglets by inducing slowly progressive haemorrhage leading to the loss of one third of the blood volume during five hours. Cardiac output, determined by thermodilution, was measured hourly as was mean blood pressure and pulse rate. Organ blood flow was determined before and at the end of the experiment with the reference sample method using radioactive microspheres. During the experiment cardiac output decreased by 33% (p less than 0.001) and mean blood pressure by 21% (p less than 0.005), the decrease being almost linear in both parameters. However, pulse rate increased only slightly. Organ blood flow decreased roughly in proportion to the decrease in cardiac output in almost all organs the decrease being significant in the spleen, antral mucosa and kidneys. Blood flow to the spleen, however, decreased significantly more while blood flow to the adrenal glands increased insignificantly. According to the results, it is obvious, that some form of vasoregulation took place during the experiment, since no frank hypovolaemic shock was observed. The present results closely resemble those observed earlier during experimental haemorrhagic pancreatitis, with the exception of greater cardiac output related decrease in organ blood flow in experimental haemorrhagic pancreatitis, suggesting that the circulatory changes during experimental haemorrhagic pancreatitis are mainly due to secondary hypovolaemia.