Detection of local metabolic changes after progressive and stepwise reduction of renal blood flow in pigs

Vascular complications after renal transplantation causing initially only partial renal ischemia can be difficult to discover in time to save the kidney. Our aims were to design an animal model allowing progressive and stepwise reduction of the arterial renal blood flow (RBF) and to investigate whether microdialysis could detect the subsequent metabolic changes.

Eight pigs were used. Two microdialysis catheters were placed, one in the lateral renal cortex, the other just outside the renal capsule. Baseline measurements were obtained at steady state. Five injections of 100 mu-polyvinyl alcohol (PVA) particles were administered once every hour through an angiographic catheter placed in the renal artery to cause the RBF to gradually decline. The glomerular filtration rate (GFR) was estimated by (51)Cr-EDTA.

One diseased animal was excluded. GFR, RBF, and all metabolites measured by microdialysis remained stable during 2 hours of baseline measurements (ANOVA; P > .05). Within 30 minutes, the first injection of PVA particles caused a reduction of RBF to 40 +/- 13% of the baseline flow (t test; P < .001 vs baseline). Significant changes in cortical lactate and glutamate as well as extracapsular glutamate were also seen, at indicating ischemia (n = 7). Cortical glucose changed 60 minutes after baseline (n = 7).

Acute, stepwise renal blood flow reduction was achieved by injection of PVA particles. An early warning of developing ischemia is provided by microdialysis. This technique could be clinically valuable because it could be instrumental in improving survival of transplanted kidneys suffering from postoperative ischemia.