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The Microcirculation Physiome
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Aleksander S. Popel and Roland N. Pittman
e motion of leukocytes through blood capillaries has also been studied thoroughly. Because leukocytes are larger and stier than RBCs, under normal ow conditions, an increase in capillary resistance caused by a single leukocyte may be orders of magnitude greater than that caused by a single RBC [79]. Under certain conditions, ow stoppage may occur, caused by leukocyte plugging. Aer a period of ischemia, RBC and leukocyte plugging may prevent tissue reperfusion (ischemia-reperfusion injury) [37]. Chemical bonds between membrane-bound receptors and endothelial adhesion molecules play a crucial role in leukocyte-endothelium interactions. Methods of cell and molecular biology permit manipulation of the receptors and thus make it possible to study leukocyte microcirculatory mechanics at the molecular level; biophysical methods allow force measurements of single adhesion bonds. ese methods open new and powerful ways to study cell micromechanics and cell-cell interactions.
Devices for donor lung preservation
Published in Expert Review of Medical Devices, 2022
Cora R Bisbee, Curry Sherard, Jennie H. Kwon, Zubair A. Hashmi, Barry C. Gibney, Taufiek Konrad Rajab
Static cold storage, or preservation of organs in an ice cooler at 4°C, remains the most used system for clinical lung transplantation. Lungs are initially flushed with a low potassium, dextran preservation solution, then immersed into the solution and stored in an ice cooler at 0–4°C until transplantation. The hypothermic environment initiates the arrest of cell function, and the preservation solution reduces cellular metabolism and provides cytoprotection [10]. While SCS is simple and cost-effective, preservation time is limited as extended periods of cold exposure increase ischemia reperfusion injury (IRI) once transplanted into the recipient. Reperfusion injury may result in inflammation, vascular leakage, reactive oxygen species, and cell death, all contributing to graft dysfunction [9]. Additionally, the inhibition of cellular metabolism eliminates the possibility for reparative processes after donor organ injury but prior to recipient implantation [9]. Lung grafts subjected to longer periods of hypothermia during SCS experience tissue damage conferring worse survival and post-operative outcomes when compared to lungs subjected to shorter periods of cold storage [11]. This hypothermia-induced tissue damage reduces the flexibility for extended preservation times when using standard 4°C static cold storage devices. Furthermore, more recent studies point to better graft function for lungs in SCS preservation at 10°C for 12 hours compared to 4°C. Preservation at 10°C could become the standard of care for prolonged pulmonary preservation in SCS, providing benefits to both patients and transplant care teams [12–14].
Intraoperative storage of saphenous vein grafts in coronary artery bypass grafting
Published in Expert Review of Medical Devices, 2019
Catherine J. Pachuk, Sophie K. Rushton-Smith, Maximilian Y. Emmert
In organ transplant, preservation solutions are used to maintain the viability of an organ prior to grafting, involving − to a significant extent − protection against IRI initiated during ischemic episodes [13–15]. The initial ischemic damage primes cells and tissues for further damage, the effects of which manifest only upon reperfusion [16]. Subsequent reperfusion does not therefore restore normality, but instead exacerbates damage incurred during ischemia [13,15]. Reperfusion injury in response to ischemic injury occurs both during the initial reperfusion phase and long-term during a prolonged reperfusion phase, the severity of which is related to the level of initial ischemic insult [17].