The influence of an agonal phase on the vascular resistance of the kidney measured during hypothermic perfusion studies

The effect of temporary clamping of the renal vessels on the vascular resistance in rabbit kidneys

In studies of 45 rabbits, either the renal artery (35 animals), or the renal artery and vein (10 animals) were clamped in situ. The effect of the clamping--of the warm ischemia--on the vascular resistance of the kidney after reestablishment of the circulation was examined in perfusion studies made after removal of the kidneys from groups of 5 animals between 1 and 5 days after revascularization. Resistance patterns were measured during hypothermic perfusion. The results confirm earlier findings that vascular resistance increases in proportion to the duration of warm ischemia up to 60 min, but not thereafter. The renal vascular resistance falls over the days following revascularization, more slowly after longer periods of ischemia. Thus after 60 min of warm ischemia the vascular resistance became normal within 24 hours, but after 180 min of warm ischemia, the normal resistance range was not reached until 96 hours after reestablishment of the circulation. When both the renal artery and the renal vein were clamped, the pattern was the same but much less emphatic. The vascular resistance never attained such high values as seen after clamping of the renal artery alone, and became normal after 24 hours of revascularization, even when the period of warm ischemia was as long as 180 min.

Vascular resistance in hypothermically perfused kidneys damaged by warm ischemia

Vascular resistance was determined during hypothermic perfusion of rabbit kidneys after various periods of warm ischemia. Ischemia was induced by clamping of the renal artery, or of the renal artery and vein, in situ. Studies were made after periods of clamping ranging from 0 to 180 min. The perfusing fluid was 5% Dextran of low molecular weight in balanced saline solution (Tis-U-Sol), with addition of 5 mg % Papaverin. When the renal artery was clamped for more than 15 min, vascular resistance increased. Maximal resistance was reached after 60 min of clamping, and was 3 times as high as that value in the control group of kidneys which were not clamped. The vascular resistance attained after 60 min of clamping did not further increase when clamping was maintained for 180 min. When both the renal artery and the renal vein were clamped vascular resistance first increased after 30 min. Maximal resistance was reached after 60 min of clamping, but was only 1/2 of that level seen when the renal artery alone was clamped.