Title Page The physiological changes of circulatory death with respect to organ donation Poppy Sarah Aldam Kings College, University of Cambridge January 2019 This dissertation is submitted for the degree of Doctor of Philosophy 1 2 Declaration This dissertation is the result of my own work and inCludes nothing whiCh is the outcome of work done in Collaboration exCept as deClared in the Preface and speCified in the text. It is not substantially the same as any that I have submitted, or, is being ConCurrently submitted for a degree or diploma or other qualifiCation at the University of Cambridge or any other University or similar institution exCept as deClared in the Preface and speCified in the text. I further state that no substantial part of my dissertation has already been submitted, or, is being ConCurrently submitted for any suCh degree, diploma or other qualifiCation at the University of Cambridge or any other University or similar institution exCept as deClared in the Preface and speCified in the text It does not exCeed the presCribed word limit for the relevant Degree Committee. Poppy Sarah Aldam Cambridge, January 2019 3 This work is dediCated to Stuart and our beautiful girls 4 Donation of organs after CirCulatory death (DCD) is re-emerging as an important sourCe of organs for transplantation worldwide, and in the United Kingdom DCD donors Comprise 39% of all deCeased organ donors. However, organs from DCD organ donors work less well after transplantation than those from brainstem dead organ donors. This inCreased prevalenCe of initial poor funCtion, despite good performanCe in the donor prior to death, suggests that Changes in donor physiology during the agonal phase, together with the subsequent period of warm isChaemia, may be responsible for the differenCes seen in organ funCtion. Although donated organs and warm isChaemia have been extensively studied, the physiologiCal Changes oCCurring in the DCD organ donor during the dying proCess remain poorly understood and ill-defined meChanistiCally. In this thesis, the physiology of the DCD donor between withdrawal of life supporting treatment and death is examined in detail for the first time in human donors. Extensive publiC and patient engagement work demonstrate publiC support for researCh in the potential organ donor, and this finding is borne out by foCus group work. Examination of a Cohort of DCD donors demonstrated previously undoCumented patterns of physiology, whiCh have signifiCant impliCations for the funCtion of transplanted organs. A key finding is the lack of ConCordanCe between arterial oxygen saturations when measured by pulse oximetry and by arterial blood gas (ABG) analysis. This has demonstrated that saturation assessment by ABG analysis doCument oxygen saturation being above generally acCepted minimal levels for up to 40 minutes longer in donors during the maximum acCepted agonal period of 240 minutes. I also present evidenCe of CardiothoraciC organ retrieval deCisions based on saturations whiCh have led to potentially transplantable organs being deClined. An investigation of markers of anaerobiC metabolism in the potential donors who do proCeed to DCD revealed Correlations between hypotension, oxygen delivery and oxygen extraction ratio, and elevated lactate levels. Further examination of the relationship between oxygen delivery and systoliC blood pressure in this Cohort demonstrate that blood pressure is Conserved in many patients beyond the point at whiCh oxygen delivery falls to CritiCal levels. This finding suggests Current organ retrieval deCisions based on systoliC blood pressure may not be best practiCe or evidenCe based. These physiologiCal Changes during the agonal period of CirCulatory death are acCompanied by Cognate Changes in human donor biology that have not previously been doCumented in DCD donors. These inClude evidenCe of sympathetiC stimulation (elevated CateCholamine levels), activation of the hypothalamiC-pituitary-adrenal axis (with Cortisol levels elevated in a subgroup surviving over 30 minutes after withdrawal of life support), and immune activation (Changes in IL-6 and TNF-a that mirror those seen in animal models of DCD donation). In ConClusion, this thesis demonstrates physiologiCal Changes not previously recorded in human subjeCts in a Cohort of DCD organ donors undergoing CirCulatory death. These Changes have impliCations for the management of potential organ donors undergoing CirCulatory death, and impact on the organs they donate. Modulation of these Changes represent a therapeutiC target, suCCessful modulation of whiCh Could translate to improved donation rates and organ transplantation outcomes. 5 6 Abbreviations ABG Arterial blood gas ADH Anti-diuretic hormone APACHE Acute Physiology and Chronic Health Evaluation BMI Body mass index BTS British Transplantation Society CaO2 Venous oxygen content CJD Creutzfeldt-Jakob disease CKD Chronic kidney disease CNS Central nervous system CVC Central venous catheter CvO2 Arterial oxygen content DBD Donation after brainstem death DCD Donation after circulatory death DGF Delayed graft function DIC Disseminated intravascular coagulation DO2 Oxygen delivery ECMO Extra corporeal membrane oxygenation FiO2 Fraction of inspired oxygen GFR Glomerular filtration rate GMC General Medical Council HIV Human immunodeficiency virus HMGB-1 High mobility group box 1 protein HPA Hypothalamic pituitary axis HRA Health Research Authority HTA Human Tissue Authority IABP Intra-aortic balloon pump ICNARC Intensive care national audit and research centre ICP Intracranial pressure ICU Intensive care unit IFN-g Interferon gamma IL-1b Interleukin 1 beta IL-6 Interleukin 6 IL-8 Interleukin 8 IL-12p70 Interleukin 12 IL-2 Interleukin 2 IL-4 Interleukin 4 MCA Mental Capacity Act NCCU Neurosciences critical care unit NHSBT NHS Blood and Transplant NICE The National Institute for Health and Care Excellent NIHR National Institute for Health Research NORS National organ retrieval service NRP Normothermic Regional Perfusion ODR Organ donor register OER Oxygen extraction ratio 7 PaCO2 Arterial partial pressure of carbon dioxide PAFC Pulmonary artery flotation catheter PaO2 Arterial partial pressure of oxygen PEEP Positive end expiratory pressure PICC Peripherally inserted central catheter QUOD Quality in organ donation initiative REC Research Ethics Committee RINTAG Research, Innovation and Novel Technology Advisory Group SaO2 Arterial oxygen saturation SNOD Specialist nurse in organ donation SOFA Sequential organ failure assessment SpO2 Pulse oximetry measurement of oxygen saturation TB Tuberculosis TNF-a Tumour necrosis factor alpha TSH Thyroid stimulating hormone VAD Ventricular assist device VO2 Oxygen consumption WLST Withdrawal of life supporting treatment 8 Acknowledgements This work would not have been possible without the help and support of a large number of people. I would like to acknowledge the following people for their Contribution to this thesis. Professor Chris Watson, my prinCiple supervisor, who has always been helpful and supportive but has pushed me to reach further with the study than I would have gone myself. In addition, for making every effort to be present for all the reCruited donors despite his own rigorous CliniCal and academiC sChedule. I Consider myself extremely fortunate to have had a prinCiple supervisor so enthusiastiC about my study and so motivated for helping me achieve my researCh goals. Professor David Menon, my co-supervisor, for inspiring my interest in anaesthetiC researCh, guiding my path from ACademiC CliniCal Fellow to PhD Candidate, and having an open door for questions and queries. I’ve never left the end offiCe without a plan of what to do next or an idea for how to do something better. Dr Charlotte Summers for being an exCellent and ever available sounding board about all things life and researCh. Dr Andrew Conway Morris for his guidanCe and enthusiasm regarding my immunology seCtion and for helping me find a struCture to the thesis when I Couldn’t see the wood for the trees. The SpeCialist Nurses in Organ Donation from Addenbrookes Hospital and the Eastern region for their work in identifying potential donors, introduCing me to donor families and helping with the logistiCs of the study, often in the early hours of the morning when they had many other responsibilities on their plates. And also, for providing Company, tea and ChoColate at 4am while waiting for theatre space. 9 Keith Burling and Peter Baker at the Core BioChemiCal Assay Laboratory for their help and guidanCe in sample ColleCtion proCedures and sample analysis, and for being inCredibly good humoured about having an amateur near their expensive equipment. The mediCal and nursing staff of NCCU and JVF at Addenbrookes hospital, for their willingness to be involved in this researCh projeCt and without whom this work would not have been possible. Theatre ODPs (in partiCular Lisa, Wendy and MalColm) for running ABG samples all night with endless good humour, providing Company and muCh needed Cups of tea. Finally, and most importantly, the donors and their families who agreed to partiCipate in this study. At a time of great physiCal and emotional stress they allowed me a window into their world for whiCh I am hugely grateful and feel very privileged. I hope that this stands as a suitable memorial to a selfless and generous group of people. Thankyou to Mark Knopfler for the musiC to write to. In his words: ‘Why worry. There should be laughter after pain. There should be sunshine after rain. These things