Ex Vivo Normothermic Perfusion of Human Upper Limbs

Abstract

Original Clinical Science-General Background. Ischemia-reperfusion injury remains a primary concern in upper extremity transplantation. Ex vivo normothermic perfusion (EVNP) enables near-physiological organ preservation, avoiding the deleterious effects of hypoxia and cooling. We investigated the effectiveness of human limb EVNP compared with static cold storage (SCS). Methods. Twenty human upper extremities were procured. Ten were perfused at 38 °C with an oxygenated red blood cell-based solution, and contralateral limbs served as SCS control (4 °C). EVNP was terminated with systolic arterial pressure ≥115 mm Hg, compartment fullness, or a 20% decline in oxygen saturation. Weight, contractility, compartment pressure, tissue oxygen saturation, and uptake rates were assessed. Perfusate fluid dynamics, gases, electrolytes, and metabolites were measured. Myocyte injury scores and liquid chromatography-mass spectrometry analysis were performed. Results. EVNP duration was 41.6 ± 9.4 h. Vascular resistance averaged 173.0 ± 29.4 mm Hg × min/L. Weight change and compartment pressures were 0.4 ± 12.2% (P = 0.21) and 21.7 ± 15.58 mm Hg (P = 0.003), respectively. Arterial and venous carbon dioxide partial pressure, oxygen saturation, and pH were 509.5 ± 91.4 mm Hg, 15.7 ± 30.2 mm Hg, 87.4 ± 11.4%, and 7.3 ± 0.2, respectively. Oxygen uptake rates averaged 5.7 ± 2.8 mL/min/g. Lactate reached 20 mmol/L after 15 (interquartile range = 6) h. Limb contractility was preserved for 30.5 (interquartile range = 15.8) h (P < 0.001) and negatively correlated with perfusate potassium (ρ = -0.7, P < 0.001). Endpoint myocyte injury scores were 28.9 ± 11.5% (EVNP) and 90.2 ± 11.8% (SCS) (P < 0.001). A significant increase in taurine (P = 0.002) and decrease in tryptophan (P = 0.002) were detected. Infrared thermography and indocyanine green angiography confirmed the presence of peripheral perfusion. Conclusions. EVNP can overcome the limitations of cold preservation by extending preservation times, enabling limb quality assessment, and allowing limb reconditioning before transplantation.

Preclinical evaluation of molecularly targeted fluorescent probes in perfused amputated human limbs

“… 30 Existing protocols used for upper extremity transplant surgery provide a useful basis for normothermic limb perfusion, but they are limited by short perfusion times and minimal use. The evolving field of vascular composite allografts (VCAs) has yet to be widely adopted, 31 and no trials to date have exceeded 10 patients. These protocols also present a fairly substantial additional cost.…”

Some Like It Hot—A Commentary to Ex Vivo Normothermic Perfusion of Human Upper Limbs

“…This could be a potential explanation for the remarkable rise of lactic acid levels in Rezaei et al’s study, whereas the measured tissue oxygenation during EMP almost reached the baseline values. 2 It remains unclear whether VCA, when preserved in static cold storage, would be accessible for muscle twitch response testing after a rewarming phase. As stated by the authors, there are no clear criteria, which define the transplantability of a VCA; thus, muscle contractility seems to be a valid option to estimate later function.…”

“…Valentin Haug, MD, 1 Yannick F. Diehm MD, 1 Ulrich Kneser MD, 1 and Bohdan Pomahac MD 2 T he shortage of suitable donors for vascularized composite allotransplantations (VCAs) is exacerbated by inadequate tissue preservation methods. Revascularization within several hours of procurement is mandatory, dramatically reducing the geographical radius for donor recruitment.…”

“…Comparability remains a challenge when it comes to different methods of EMP of human VCAs. Rezaei et al 2 compared the effects of normothermic EMP of 20 human upper extremities versus static cold storage. The main differences in the settings of working groups examining the effects machine perfusion has on VCA are the composition of the perfusion solution, the temperature and pressure settings, and the setup of the machine itself.…”

Weight gain is an early indicator of injury in ex vivo normothermic limb perfusion (EVNLP)

“…7 Ex vivo normothermic limb perfusion (EVNLP) aims at maintaining physiological cellular metabolism while avoiding cold injury, ischemia reperfusion injury (IRI), and allowing for viability assessment. 8 In a 2022 study by Rezaei et al, human limbs were preserved using EVNLP for 41 ± 9.3 h, maintaining contractility for 30.5 ± 15.8 h. 9,10 On histological analysis, EVNLP limbs showed less evidence of myocyte damage than SCS control limbs. Rohde et al demonstrated presence of active metabolism throughout 24-h EVNLP.…”