Clinical Study On The Effect Of Renal Ischemia Time On GFR

Objective: The time of kidney warm ischemia should not exceed thirty minutes in the traditional view,otherwise the irreversible damage of renal function would happen.The effect of different times of kidney warm ischemia on long-term glomerular filtration rate(GFR)was studied in this research to illustrate that the maximum tolerable time of warm ischemia of kidney was more than 30 minutes and provide the technology support to extend the time of renal artery clamping reasonably.Methods: 51 medical records of renal artery clamping and partial nephrectomy under laparoscopic were analyzed retrospectively.These records were divided into four groups according to the different time of renal artery clamping(kidney warm ischemia).Group A(15 cases): The duration of warm ischemia were less than thirty minutes and the average time was 19.87±5.34 min.Group B(12 cases): The duration of warm ischemia were more than or equal to thirty minutes and less than forty minutes,and the average time was 31.58±2.68 min.Group C(12 cases): the duration of warm ischemia was more than or equal to forty minutes and less than fifty minutes,and the average time was 44.25±2.83 min.Group D(12 cases): the times of warm ischemia were more than or equal to fifty minutes and the average time was 67.58±22.90 min.The time of warm ischemia in the traditional view was defined as control group(Group A);Group B,C and D were experimental groups.Comparing the differences in long-term GFR among these groups.GFR was eGFR which was converted by Asian formula CKD-EPI with serum creatinine values.The main factors which affected the GFR after renal artery clamping and partial nephrectomy under laparoscopic were:(1)the damage of warm ischemia,(2)the volume loss of kidney during surgery.It showed that the decreased ratio of GFR after surgery was equal to the volume loss of kidney in reasonable ischemia time,so that the ratio of residual kidney after surgery could be calculated by CT and the glomendar filtration rate(estimated eGFR)after surgery which was only affected by volume loss could be estimated.But in fact,the GFR after surgery was suffered from different damage of warm ischemia.The glomendar filtration rate(real eGFR)after surgery was calculated by hydroxyproline,which was affected by the volume loss of kidney and the damage of warm ischemia at the same time.Comparing the real and estimated eGFR in each group.The damage of warm ischemia could be thought to cause the decline of renal function after surgery if the real eGFR was decreased and more than estimated eGFR,and the ratio of decreasing was more than 10%.Results:(1)The real eGFRs after surgery in each ischemia groups were less than the estimated eGFR,but the ratio of decreasing of Group D was more than control group.The result of difference had statistical significant(P<0.05).(2)Among those groups which the ratio of decreasing that the real eGFR was less than estimated eGFR was more than 10%,Group D had higher ratio than other groups,and the result of difference had the statistical significant(P<0.05).Conclusion: The research proved that the maximum tolerable time of warm ischemia of kidney was more than 30 minutes.The irreversible damage of renal function after LPN only happened when the time of warm ischemia was more than 50 minutes,which meant that damage of warm ischemia decreased the GFR of kidney.