Different impact of normo- and hypotensive brain death on renal macro- and microperfusion--an experimental evaluation in a porcine model.

Abstract

Despite the growing use of kidneys from living donors, organs harvested from brain dead donors are the dominant graft types used in renal transplantation. It is accepted that brain death (BD) has a damaging effect on the renal allograft, with a lower graft survival. Amongst various causes, changes in renal microperfusion could be responsible. Renocortical microperfusion was assessed during BD using thermal diffusion in a porcine model. Two types of BD were induced in two groups of pigs [hypotension (Hypo-BD): n = 11; normotension (Normo-BD): n = 10] and compared to controls (n = 5) over a period of 210 min. We analysed systemic parameters [heart rate (HR), mean arterial blood pressure (MAP)], aortic blood flow (ABF) and renal perfusion [renal artery blood flow (RABF) and renocortical blood flow (RCBF)]. Following the two distinct forms of BD induction, a stable normo- or hypotension was observed. Haemodynamic parameters were only slightly changed (control group: MAP, 62+/-2 mmHg; HR, 95+/-3/min; Normo-BD: MAP, 56+/-4 mmHg; HR, 104+/-8/min; Hypo-BD: MAP, 43+/-3 mmHg; HR, 112+/-7/min). Solely dependent on systemic haemodynamics, RABF and RCBF decreased in the Hypo-BD (RABF: 142+/-19 to 94+/-9 ml/100 g/min; RCBF: 80+/-4 to 52+/-2 ml/100 g/min), while in Normo-BD group RABF mildly changed (158+/-13 ml/100 g/min) and RCBF decreased slightly from 76+/-3 to 70+/-6 ml/100 g/min. As opposed to the Normo-BD group, animals with Hypo-BD showed a significant decrease in RABF (reduction of 34%) and RCBF (reduction of 35%) with a sharp drop of MAP (reduction of 25%), however ABF remained relatively constant. In this model, a reduction of renocortical microperfusion in brain dead pigs was only found during haemodynamic instability (hypotension) and could not be attributed to BD as such. Our findings would support intensive cardiocirculatory stabilization for potential BD donors in order to minimize kidney preservation damage.