Enhanced heart rate response to haemorrhage by ileus in the pig

Effects of ileus on cardiovascular and hormonal responses to haemorrhage were evaluated in 10 anaesthetized pigs. Ileus was induced and the bleeding sequence repeated on the following day. Before ileus, a resting heart rate (HR) of 105 (range 83-140) beats min-1 remained unchanged until haemorrhage amounted to 15% of the blood volume. With a blood loss of 28% HR increased to a maximum of 162 (126-245) beats min-1. In contrast, ileus increased HR upon initiation of haemorrhage from a similar resting value to a maximum of 200 (152-250) beats min-1 (P < 0.0005). There were neither statistical differences in mean arterial pressure, cardiac output, central venous pressure, thoracic electrical impedance, pulmonary arterial mean pressure, pulmonary wedge pressure, pulmonary and systemic vascular resistances, nor in plasma concentrations of dopamine, adrenaline, vasopressin and aldosterone during haemorrhage before and after ileus. Plasma noradrenaline increased more with haemorrhage after than before ileus: from 2.8 (1.2-5.0) to 13 (2.3-59.0) vs. 3.0 (1.5-4.2) to 3.6 (2.7-17.5) nmol l-1 (P < 0.005). Also, the pancreatic polypeptide response to haemorrhage was enlarged with ileus (29 (0-60) to 90 (45-145) vs. 23 (0-64) to 57 (27-106) pmol l-1 (P < 0.005)). No significant differences could be detected in cardiovascular and hormonal responses to haemorrhage before and after a sham-operation in three pigs. Results demonstrate an immediate and enhanced HR response to haemorrhage in the pig with ileus, reflected in sympathetic activation as indicated by plasma noradrenaline.