Introduction: There have been multiple studies on the effects of cold and warm ischaemia time on graft function after kidney transplantation. An extended cold ischaemia time (CIT) or extended warm ischaemia time (WIT) have independently been shown to adversely affect graft survival. However, there are few studies which have analysed both cold and warm ischaemia times. We aimed to determine if a composite measure of cold and warm ischaemic time had a significant association with graft function.
Methods: All kidney transplants performed at our center between April 2017 and March 2018 were analysed, and cases were excluded where CIT, WIT, or 1 year creatinine measurements were not available. A total of 107 cases were included in the analysis. We used a cutoff of 15 hours for CIT and 35 minutes for WIT.
We compared mean 1 year creatinine for groups with long vs short CIT and long vs short WIT. We also analysed the effect of CIT and WIT on delayed graft function. Cases were also separated into four groups based on length of CIT and WIT (low CIT/low WIT, low CIT/high WIT, high CIT/low WIT, high CIT/high WIT). The mean 12 month creatinine between each group was also compared.
Results and Discussion: In our cohort of patients, there were a relatively a small number of patients with a long CIT >15 hours (n=17) compared to CIT <15h (n=86). However an extended CIT of 15 hours had a significantly increased mean creatinine at 12 months (173 vs 148 µmol/L, p=0.02) compared to CIT <15 hours. Grafts with WIT>35 minutes also had a significantly raised creatinine compared to WIT <35 minutes (64 vs 131 µmol/L, p=0.006).
When cases were divided into 4 groups, there was a significant difference in mean creatinine in grafts with long CIT/long WIT compared to all other groups. There was no difference in mean creatinine between the other groups. There was also no difference in DGF between any groups. The differences in high CIT/high WIT and high CIT/low WIT were greatest (mean difference 87 µmol/L, p=0.012), followed by low CIT/low WIT (76 µmol/L, p=0.001), and finally low CIT/high WIT (mean difference 53 µmol/L, p=0.04). An extended cold and warm ischaemia time is associated with the worst graft function at one year, but the results suggest that WIT may have a greater impact on long term graft function than CIT.
Conclusion: The duration of WIT and CIT have previously been shown to adversely affect graft function. A composite measure of CIT and WIT may be useful in predicting longer term outcomes in kidney transplantation. Our study suggests that WIT has a greater impact on graft function than CIT, and that maintaining CIT <15h and WIT <35 minutes is associated with improved one year creatinine.