Experimental study in bile duct-ligated rats of vasopressin and preoperative volume loading to prevent hypotensive crises

Background. Systemic hypotension may result in postoperative renal failure in jaundiced patients. Attenuated responsiveness to catecholamines and hypovolaemia has been reported in jaundiced animals and may be a mechanism contributing to the increased susceptibility of jaundiced patients to haemorrhagic shock. This suggests that an alternative to vasoactive amines to control perioperative hypotension could be desirable. Methods. This study evaluated the pressor response to vasopressin in normovolaemic 3-day bile duct-ligated rats and in 3-day bile duct-ligated rats after an acute controlled haemorrhage. It also evaluated the response after volume loading with 0.9 per cent saline, 7.5 per cent saline, colloid and mannitol before controlled haemorrhage. In addition, blood volume was measured using radiolabelled albumin. All the data obtained from bile duct-ligated rats were compared with data from sham-operated animals. Results. Attenuated pressor responses to vasopressin were not observed in either normotensive bile duct-ligated rats or in bile duct-ligated rats subjected to controlled haemorrhage. Volume loading with the four fluids over the dosing range 2.5-7.5 μl per g body-weight in bile duct-ligated rats reversed the susceptibility to haemorrhagic hypotension. Conclusion. Although no reduction in blood volume was demonstrated, bile duct-ligated rats may have a reduced effective blood volume manifesting itself as a latent hypovolaemia and/or tendency to hypotension. Preoperative fluid loading could be beneficial because it corrects hypovolaemia and improves cardiovascular function, as well as improving the cardiovascular response to haemorrhage.