Normothermic Regional Perfusion: Why Isn't the Lactate Coming Down?

Area of Science:

• Organ transplantation
• Cardiovascular surgery
• Physiology

Background:

• Lactate is a key liver viability marker during normothermic regional perfusion (NRP).
• Stored red blood cells (pRBCs) continue producing lactate, potentially confounding NRP lactate measurements.
• The age of transfused pRBCs can influence lactate levels in the NRP circuit.

Purpose of the Study:

• To investigate the impact of stored red blood cell age on lactate levels during NRP.
• To determine if pRBC age correlates with lactate concentrations in the NRP perfusate.
• To assess the clinical implications for liver viability assessment in donation after circulatory death (DCD) donors.

Main Methods:

• Prospective study of 16 DCD donors undergoing NRP.
• Lactate levels measured in pRBC bags before transfusion.
• Serial lactate measurements of the NRP circuit perfusate every 15 minutes.

Main Results:

• pRBC lactate levels ranged from 4.4 mmol/L to >20 mmol/L, strongly correlating with blood age (r² = 0.74).
• Donors receiving newer pRBCs (≥20 days from expiration) showed significantly lower 60-minute NRP lactate compared to those receiving older pRBCs (<20 days from expiration) (4.0±2.0 mg/dL vs. 6.3±2.3 mg/dL; p = 0.048).

Conclusions:

• The age of stored red blood cells is a significant factor affecting lactate levels during NRP.
• Clinicians should consider older pRBC transfusion as a potential reason for non-decreasing lactate levels.
• Further lactate assessment or extended perfusion (NRP/NMP) may be warranted before declining a liver based solely on lactate trends.