What is the recommended warm ischaemia time to prevent tissue damage and organ dysfunction?

Warm Ischemia Time Thresholds to Prevent Tissue Damage and Organ Dysfunction

For donation after circulatory death (DCD) liver transplantation, true warm ischemia time should not exceed 20-30 minutes, and total warm ischemia time should remain under 30-45 minutes to prevent increased complications and organ dysfunction. 1

Organ-Specific Warm Ischemia Time Limits

Liver Transplantation

The most critical thresholds for DCD liver transplantation are:

• True warm ischemia time (interval from significant ischemic insult such as mean arterial pressure <60 mmHg to cold perfusion): ≤20-30 minutes 1
• Total warm ischemia time (interval from withdrawal of life support to cold perfusion): ≤30-45 minutes 1, 2
• Cold ischemia time: ≤8-10 hours 1, 2
• Recipient warm ischemia time (anastomotic time from removal from cold storage to reperfusion): <90 minutes 1, 2

The American Society of Transplant Surgeons emphasizes that the time from first reduction of systolic blood pressure to <50 mmHg until cold flush (sBP 50-interval) should be recorded for all DCD donors to accurately assess functional warm ischemia time. 1

Kidney Transplantation

For DCD kidney transplantation:

• Total warm ischemia time: ≤45-60 minutes 1
• Functional warm ischemia time (time from systolic blood pressure <50 mmHg to cold flush): <30 minutes is optimal 3
• Cold ischemia time: ≤24 hours 1
• Recipient warm ischemia time: Each 10-minute increment beyond 20 minutes increases the hazard ratio for death/graft failure progressively, reaching 1.23 for times ≥60 minutes 4

Research demonstrates that 94.4% of DCD kidney donors with total warm ischemia time between 0.5-2 hours maintained functional warm ischemia time <30 minutes, suggesting that functional warm ischemia time may be more predictive of outcomes than total warm ischemia time alone. 3

Pancreas Transplantation

For DCD pancreas transplantation:

• Total warm ischemia time: ≤45-60 minutes 1
• Cold ischemia time: ≤18 hours 1

Surgical Timing Requirements

The American Society of Transplant Surgeons provides specific operative time limits:

• Donor hepatectomy time (flush/cross-clamp to placement in hypothermic solution): ≤30 minutes 1
• Kidney extraction time (flush/cross-clamp to placement in hypothermic solution): ≤60 minutes 1
• Time from incision to cold flush in combined thoracic/abdominal procurements: 2-3 minutes maximum unless washed banked blood is prepared in advance 1

Critical Time Points for Documentation

The 2023 American Society of Transplant Surgeons guidelines mandate recording these specific time points: 1

• Time of withdrawal of life-sustaining treatment
• Time heparin is administered
• First minute when SpO₂ drops to <70%
• First minute when systolic blood pressure drops to <50 mmHg (critical for functional warm ischemia time calculation)
• Time of circulatory arrest determination
• Time of incision
• Time of cold flush/cross-clamp
• Time of organ removal

Strategies to Minimize Warm Ischemia Time

To optimize outcomes, implement these evidence-based practices:

• Preferentially perform withdrawal of life support in the operating room after prepping and draping 1
• Administer heparin before withdrawal rather than at onset of the agonal phase 1
• Limit mandatory "no-touch" time to ≤5 minutes after circulatory arrest declaration to avoid unnecessary warm ischemic injury 1
• Monitor blood pressure, heart rate, and oxygenation every minute during the agonal phase 1
• Use experienced DCD procurement teams familiar with rapid surgical techniques 1

Important Caveats

A common pitfall is using ambiguous terminology. The term "donor warm ischemia time" (DWIT) should be avoided due to its ambiguity; instead, specify "functional DWIT" and clearly define which measurement is being used. 1

For uncontrolled DCD (cardiac arrest donors), acceptable warm ischemia times are substantially longer than controlled DCD, with total warm ischemia (no-flow plus low-flow periods) ranging from 120-150 minutes when appropriate preservation techniques are employed. 1 However, this applies only to specific protocols with extracorporeal membrane oxygenation support and should not be extrapolated to standard DCD procurement.

The combination of prolonged warm ischemia time with other risk factors (donor age ≥65 years, cold ischemia time >8 hours, hepatic steatosis) significantly compounds the risk of graft failure and should be carefully considered when accepting organs. 1