Normothermic Machine Perfusion (NMP) in Liver Transplantation: Evidence and Cases

Understanding Normothermic Machine Perfusion (NMP)

• 💡 Normothermic machine perfusion (NMP) involves perfusing donor organs with oxygenated, nutrient-rich blood at normal body temperatures outside the body.
• 🎯 This contrasts with traditional static cold storage, which uses cold preservation solutions at hypothermic temperatures to reduce metabolic rate and energy requirements.
• 🚀 The theory behind NMP is to mimic physiological conditions, potentially reducing ischemia-reperfusion injury and increasing the utilization of marginal or extended criteria donors.

Key Clinical Trials: PROTECT and Chapman et al.

• 🔬 The PROTECT trial (2022) compared NMP using the OCS liver device to static cold storage in deceased donor liver transplantation.
• ✅ Results showed NMP was associated with improved early outcomes, including lower rates of early allograft dysfunction and reduced non-anastomotic biliary complications.
• 📈 The Chapman et al. trial (2023) aimed to assess NMP's benefit in routine practice, hypothesizing it would particularly help high-risk donors.
• ⚠️ While the overall primary outcome (early allograft dysfunction) was not significantly different, NMP showed significant benefits for high-risk organs, such as those from DCD donors or with a high donor risk index.

NMP in Clinical Practice and Case Examples

• 📌 In a 2017 case without NMP, a DCD liver transplant resulted in ischemic cholangiopathy, highlighting the risks associated with traditional preservation for these grafts.
• ⚡ When using NMP in a similar DCD donor case in 2025, assessment involved monitoring lactate levels, bile production, and perfusion dynamics to evaluate graft function.
• 📊 A starting lactate of 11, decreasing to 7 at 2 hours, would prompt further monitoring and assessment of other parameters like flow and bile production, rather than immediate rejection.
• ⚠️ A 27-year-old brain-dead donor with a BMI of 31 for a redo liver transplant recipient (MELD 34) could benefit from NMP to allow for extended recipient hepatectomy time and logistical flexibility.
• 📈 For a 66-year-old DCD donor with 30% macrosteatosis and a BMI of 35, NMP could provide reassurance and a tool to assess the graft's viability before transplantation, given the increasing need to utilize less ideal organs.

Evolving Trends and Future Directions

• 🚀 The number of deceased donor after cardiac death (DCD) donors has significantly increased, driving the need for advanced preservation techniques like NMP.
• 📈 NMP is becoming a crucial tool for assessing and utilizing high-risk grafts, expanding the donor pool and potentially saving more lives.
• 🧩 While pivotal trials have specific inclusion criteria, NMP is increasingly being used off-label in complex cases, requiring careful patient-driven rationale.
• ⚠️ The field is continuously pushing the envelope to use more organs, balancing the need to save lives with the inherent risks of transplanting less ideal grafts.