From the Guidelines
In renal transplantation, minimizing both warm and cold ischemia times is critical for optimal graft outcomes, with warm ischemia time (WIT) ideally kept under 30 minutes and cold ischemia time (CIT) limited to under 24 hours, preferably less than 18 hours, as supported by the most recent evidence 1.
Key Considerations
- Warm ischemia time (WIT) refers to the period when the kidney has no blood supply at body temperature, occurring during procurement from the donor and during anastomosis in the recipient.
- Cold ischemia time (CIT) represents the period when the kidney is preserved in cold solution between procurement and implantation.
- Extended CIT beyond 24 hours significantly increases the risk of delayed graft function, while each hour of WIT substantially raises the likelihood of graft failure, as noted in studies such as 1 which highlights the importance of minimizing ischemia times for optimal renal function post-surgery.
Ischemia Time Recommendations
- Warm ischemia time should be kept under 30 minutes to minimize the risk of graft failure, as prolonged WIT is associated with diminished postoperative eGFR 1.
- Cold ischemia time should be limited to under 24 hours, preferably less than 18 hours, to reduce the risk of delayed graft function, with some studies suggesting that even shorter CITs may be beneficial 1.
Modern Preservation Techniques
- Machine perfusion can better maintain organ viability during storage compared to static cold storage, especially for marginal donor kidneys or those with expected prolonged CIT, as discussed in the context of combined liver-kidney transplantation 1.
Clinical Implications
- Minimizing ischemia times is crucial for optimal graft outcomes, and clinicians should strive to keep WIT and CIT as short as possible to reduce the risk of graft failure and delayed graft function, in line with recommendations from recent studies 1.
From the Research
Warm Ischemia Time and Cold Ischemia Time in Renal Transplant Surgery
- Warm ischemia time refers to the period during which the kidney is not perfused with blood at body temperature, typically occurring during the implantation of the graft 2.
- Cold ischemia time, on the other hand, refers to the period during which the kidney is preserved at a lower temperature, usually during transportation or storage before transplantation 3, 4, 5, 6.
Effects of Ischemia Time on Graft Function
- Prolonged cold ischemia time has been associated with delayed graft function, especially in expanded criteria donors, and possibly an increased acute rejection rate 3.
- Warm ischemia time during implantation has also been shown to impact early graft function, with longer times leading to poorer outcomes 2.
- Ischemia/reperfusion injury, which occurs when the kidney is reperfused after a period of ischemia, can lead to inflammation, oxidative stress, and cellular damage, ultimately affecting graft survival 4, 6.
Strategies to Minimize Ischemia Time
- Machine perfusion, also known as pump machine perfusion, has been shown to reduce delayed graft function and improve long-term graft survival 4.
- The use of antilymphocyte antibody therapy before reperfusion has also been studied as a potential strategy to prevent ischemia/reperfusion injury 4.
- Minimizing warm ischemia time during implantation, for example by optimizing surgical techniques, may also help to improve early graft function 2.