From the Guidelines
Warm ischemia time (WIT) should be minimized to less than 30 minutes, and cold ischemia time (CIT) should be less than 24 hours to optimize outcomes in renal transplantation, as prolonged ischemia times are associated with delayed graft function, acute rejection, and reduced long-term graft survival 1. In renal transplant surgery, WIT and CIT are critical factors that affect graft outcomes. WIT refers to the period when the kidney lacks blood supply at body temperature, and CIT begins when the organ is cooled with preservation solution and ends when it's removed from cold storage for implantation.
Key Considerations
- WIT should be minimized to prevent tissue damage, with a recommended duration of less than 30 minutes in living donor transplants.
- CIT should be less than 24 hours, as longer CIT is associated with delayed graft function, acute rejection, and reduced long-term graft survival.
- Preservation solutions like University of Wisconsin (UW), histidine-tryptophan-ketoglutarate (HTK), or Custodiol can be used to reduce metabolic demands during cold storage.
- Machine perfusion can extend safe preservation time compared to static cold storage.
Recommendations
- Surgeons should aim to minimize both WIT and CIT through efficient procurement techniques, coordinated surgical timing, and rapid recipient preparation.
- The damaging effects of prolonged ischemia occur through mechanisms including ATP depletion, calcium overload, free radical formation, and inflammatory responses during reperfusion.
- Kidneys from expanded criteria donors are particularly sensitive to prolonged ischemia times, requiring even more careful management of these intervals.
Evidence-Based Practice
- The American Society of Transplant Surgeons recommends standardizing the terminology of warm ischemia time and avoiding the term DWIT due to its ambiguity 1.
- The use of NRP in the United States is considered an acceptable practice available to procure organs from DCD donors, and postmortem A-NRP and TA-NRP are safe and feasible in DCD organ procurement 1.
- The evidence suggests that warm ischemia time longer than 60 min leads to significant exponential losses in kidney function 1.
From the Research
Warm Ischemia Time and Cold Ischemia Time in Renal Transplant Surgery
- Warm ischemia time and cold ischemia time are crucial factors in renal transplant surgery, as they can significantly impact graft function and patient outcomes 2, 3, 4, 5, 6.
- Prolonged warm ischemia time during anastomosis has been shown to be an independent predictor of delayed graft function in kidney transplant recipients 6.
- Cold ischemia time is also an important factor, with studies suggesting that it can affect graft function and patient outcomes 3, 5.
- The impact of warm ischemia time on graft function can be significant, with longer times associated with poorer early graft function and a higher risk of delayed graft function 5, 6.
- However, the long-term effects of warm ischemia time on graft function may be limited, with some studies suggesting that it has little impact on serum creatinine levels at 3 months or later 5, 6.
Factors Affecting Warm Ischemia Time
- Recipient body mass index (BMI) and the presence of multiple arteries in donor kidneys can prolong implantation time and increase warm ischemia time 5.
- The surgical technique and immunosuppression protocols used can also impact warm ischemia time and graft function 6.
- Minimizing warm ischemia time during anastomosis is important to reduce the risk of delayed graft function and the need for dialysis in the perioperative period 6.
Cold Ischemia Time and Graft Function
- Cold ischemia time can affect graft function, with longer times associated with poorer early graft function and a higher risk of delayed graft function 3, 5.
- The use of pump machine perfusion and antilymphocyte antibody therapy can help reduce the impact of cold ischemia time on graft function 2.
- Standardizing cold ischemia time is important to ensure consistent injury in experimental models of kidney transplantation 3.