How does the metra work?

During normothermic machine perfusion with the OrganOx metra, the donor liver is continuously perfused with oxygenated blood, medications and nutrients at normal body temperature and near physiological pressures and flows.

This means the liver is functional throughout preservation, enabling functional assessment and evidence-based decisions on whether to transplant a donor organ.


Oxygen is concentrated from ambient air and supplied, on-demand to the oxygenator. The blood is also warmed by the on-board heater.


Blood is drawn from the liver by a centrifugal pump, which automatically varies in speed according to changes in blood pressure.

OrganOx Diagram


Warm, oxygenated blood is stored in the soft-shell reservoir, and supplied to the liver under near-physiological pressure.

Medicines & nutrition

Medicines and nutrition are delivered automatically throughout perfusion, in order to minimise operator hands-on time.

Assessment of liver function prior to transplant with the metra may result in more donor livers being available for transplant.1

Conventional cold preservation involves storage of the liver at 4°C and aims to minimise liver degradation. The metra, however, recreates a near physiological environment by continuously perfusing the liver at near physiological pressures and flows with oxygen-carrying red blood cells at 37°C. The liver remains functional during preservation, producing bile, metabolising glucose and maintaining pH, allowing the objective assessment of organ performance prior to transplant. 1,2

Via onboard blood gas analysis, the metra automatically measures and controls blood gases in the perfusate without user intervention.


Fully automated and simple to use

  • Pre-assembled sterile disposable perfusion circuit for ease of connection and disposal.
  • Transportable battery powered device.
  • Graphical User Interface with real time parameters.
  • Self regulating oxygen supply: No need for gas canisters.
  • Single-button operation for ease of use.
  • Single priming port for hands-off and rapid circuit priming.
  • Continuous and automated monitoring of bile production.
  • Robust and transportable device.


The metra has a rugged, robust design for ease of transport and safe storage when not in use. It has a battery for transportation when not on mains power and a self-regulating oxygen supply, removing the need to carry gas canisters.


The metra has a simple control panel with just three main buttons: start, stop and remove cartridge. The onboard automation allows automated control of flows, pressures, temperature and blood gases, providing the same perfusion conditions every time. 


Simplicity of use is paramount in a clinical setting and the metra's fully automated perfusion system provides this. The sterile disposable circuit is pre-assembled making it simple and rapid to prime as well as being easy to dispose of after the procedure.


Rapid Setup

All connectors are simple and rapid to use, ensuring that preparation time is minimal. The metra self primes under gravity in less than 15 minutes.

Maximise transplant logistics with the metra

Clinical evidence has been generated using the metra in two ways: transport mode1 (continuous NMP) or “back to base” mode (NMP following static cold storage)3,4 offering transplant centres maximum flexibility of use.

Want to know more about the metra?

If you would like to know more about the metra and how it may benefit your liver transplantation unit, click ‘Contact Us’ and a member of the OrganOx team will be in touch.

Contact Us


References: 1. Nasralla D et al. Nature 2018; 557(7703):50–56. 2. Jayant K et al. Exp Rev Gastroenterol Hepatol 2018;12:1045–1058. 3. Ceresa CDL et al. Liver Transpl 2019; [Epub ahead of print]. 4. Bral M et al. Liver Transpl 2019; 25(6):848–858.

UK/US MD-040-7-1 - September 2022