Title
Membrane lung exhaust carbon dioxide monitoring to guide fresh gas flow management during normothermic regional perfusion
First and Presenting author
Marta Velia Antonini MSc m.antonini@unibo.it
Department of Medical and Surgical Sciences (DIMEC), University of Bologna, Bologna, Italy
Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Co-authors
Alessandro Circelli MD Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Giovanni Scognamiglio MD Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Alessandra Venditto MD Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Emiliano Gamberini MD Intensive Care Unit, Morgagni – Pierantoni Hospital, AUSL della Romagna, Forlì, Italy
Giuseppe Tarantino MD Emilia-Romagna Transplant Reference Centre, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy
Mattia Carnelli MD Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Giampaolo Orsolini MD Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Tiziana Digiacomo MD Intensive Care Unit, Infermi Hospital, AUSL della Romagna, Rimini, Italy
Bernardo Caldini MD Intensive Care Unit, Santa Maria delle Croci Hospital, AUSL della Romagna, Ravenna, Italy
Maria Laura Marzi MD Intensive Care Unit, Umberto I Hospital, AUSL della Romagna, Lugo, Italy
Mirko Belliato Prof Cardiothoracic Anesthesia and Intensive Care, Cardiothoracovascular Department, IRCCS Policlinico San Matteo Foundation, Pavia, Italy
Vanni Agnoletti Prof Intensive Care Unit, Bufalini Hospital, AUSL della Romagna, Cesena, Italy
Introduction
Normothermic regional perfusion (NRP) is a strategy of extracorporeal support implemented in donors undergoing circulatory determination of death (DCDDs).
Similar to conventional extracorporeal membrane oxygenation (ECMO), the circuit membrane lung (ML) is extremely effective in clearing CO2 from the blood. The sweep gas flow (SGF) is the major determinant of ML CO2 removal (VMLCO2). During abdominal NRP (NRP) if the native lung are not ventilated, the ML is the only determinant of CO2 removal. An increase in the SGF will decrease partial pressure of CO2 at the ML gas outlet (EMLCO2 ), increasing the pressure gradient in between blood and gas phase, so increasing VMLCO2.
Methods
We aimed to assess the feasibility and effectiveness of PEMLCO2 continuous monitoring to guide SGF management during NRP. We used the conventional CO2 monitoring in use on the patient before withdrawal of life sustaining measures (monitor, sensor, cuvette). The cuvette was connected to the ML using “waste” tubings from the extracorporeal circuit (a schematics of connections and devices is included in figures A-B). Both capnogram “waveform” (continous due to continuous SGF inside the ML gas pathway) and numeric PEMLCO2 value in mm Hg were monitored during NRP.
The PEMLCO2 value was used to adapt SGF (volume in liter per minute, provided to the ML gas inlet). The partial pressure of CO in the blood exiting the ML (PEMLCO2) was recorded at NRP initiation and every 30 minutes. The waveform was used to detect complications as the presence of condensation in the exhaust gas tubing.
The formula to calculate VMLCO2 from PEMLCO2 has been previously described for ECMO (figure B).
Results
We implemented continuous PEMLCO2 monitoring in 10 DCDDs undergoing abdominal NRP (native lungs did not undergo mechanical ventilation, so ML was the sole determinant of CO2 removal). Detailed data on PEMLCO2, SGF, PPOST-MLCO2, VMLCO2 are included in figure C-D.
Conclusions
Non-invasive PEMLCO2 monitoring appears feasible, allowing for prompt SGF optimization if modified blood PCO2 is suspected between blood analyses, potentially improving NRP safety.
All the devices used to implement PEMLCO2 monitoring are commonly available in any intensive care unit or operating room. In our experience, all of these were used on the patients antemortem; procedural costs were unaffected.
