Background. Normothermic machine perfusion (NMP) bears the potential for significant prolongation of liver preservation before transplantation. Although safety and feasibility have been recently published, no data are available describing the significant challenges of establishing NMP programs outside clinical studies. We herein present our experience and propose a multidisciplinary approach for liver NMP in the clinical routine. Methods. In February 2018, liver NMP was introduced for routine use in marginal organs, logistic challenges, and complex recipients at our institution. In a multidisciplinary effort among transplant coordinators, perfusionists, transplant surgeons, anesthesia, nurses, blood bank as well as laboratory staff, a clinical routine was established and 34 NMP cases were performed without critical incidents or organ loss. Results. Nine livers were discarded due to poor organ quality and function observed during NMP. Twenty-five livers were successfully transplanted after preservation of up to 38 h. The extended criteria donors rate was 100% and 92% in discarded and transplanted livers, respectively. Nighttime procedures and parallel transplantations were eventually omitted. Graft and patient survival was 88% at 20 mo. No cholangiopathy was observed despite the use of extended criteria donor organs in 92% of cases. Conclusions. NMP in a multidisciplinary approach enables a safe prolongation of liver preservation and overnight organ care. A first field test of NMP indicates safety and benefit of this approach.
-Hematocrit (Hct) of awake hamsters and CD-1 mice was acutely increased by isovolemic exchange transfusion of packed red blood cells (RBCs) to assess the relation between Hct and blood pressure. Increasing Hct 7-13% of baseline decreased mean arterial blood pressure (MAP) by 13 mmHg. Increasing Hct above 19% reversed this trend and caused MAP to rise above baseline. This relationship is described by a parabolic function (R 2 ϭ 0.57 and P Ͻ 0.05). Hamsters pretreated with the nitric oxide (NO) synthase (NOS) inhibitor N -nitro-L-arginine methyl ester (L-NAME) and endothelial NOS-deficient mice showed no change in MAP when Hct was increased by Ͻ19%. Nitrate/nitrite plasma levels of Hct-augmented hamsters increased relative to control and L-NAME treated animals. The blood pressure effect was stable 2 h after exchange transfusion. These findings suggest that increasing Hct increases blood viscosity, shear stress, and NO production, leading to vasodilation and mild hypotension. This was corroborated by measuring A1 arteriolar diameters (55.0 Ϯ 21.5 m) and blood flow in the hamster window chamber preparation, which showed statistically significant increased vessel diameter (1.04 Ϯ 0.1 relative to baseline) and microcirculatory blood flow (1.39 Ϯ 0.68 relative to baseline) after exchange transfusion with packed RBCs. Larger increases of Hct (Ͼ19% of baseline) led blood viscosity to increase Ͼ50%, overwhelming the NO effect through a significant viscosity-dependent increase in vascular resistance, causing MAP to rise above baseline values. nitric oxide; shear stress; vascular resistance; hypertension IT IS A GENERAL MEDICAL and clinical perception that an increase in blood viscosity may lead to short-and long-term negative physiological conditions, and there appears to be universal agreement that increased blood viscosity is a factor in hypertension. Lowering blood viscosity, however, is not advocated as a means for controlling hypertension with the exception of erythrocytosis, substantial Hct increases consequent to adaptation to high altitudes, and cardiovascular impairment in premature infants. These conditions represent extremes of an increase in blood viscosity and clearly must be corrected by lowering Hct, because the extreme excess of red blood cells (RBCs) is superfluous in providing adequate oxygen-carrying capacity and is in fact a hindrance to blood flow and therefore oxygen delivery.Clinical studies (14, 37) report a significant relationship between hypertension and high Hct levels. Hypertensive patients have higher Hct values than normotensive control individuals (23). Patients suffering from polycythemia vera or other erythrocytoses present with pathologically high Hcts leading to hypertension, thromboembolism, and other severe clinical complications (2, 15). There is evidence, however, that individuals, such as Peruvian miners, survive with Hct levels of 75-91% (18), suggesting the existence of an adaptive mechanism.Endothelial cells play a key role in the regulation of blood pressure and blood flow beca...
During haemodilution, substitution of fibrinogen and PCC causes an enhancement of coagulation and final clot strength. This reversal of dilutional coagulopathy may reduce blood loss and mortality when large amounts of colloids are needed to maintain normovolaemia during huge blood losses.
Cabrales, Pedro, Judith Martini, Marcos Intaglietta, and Amy G. Tsai. Blood viscosity maintains microvascular conditions during normovolemic anemia independent of blood oxygen-carrying capacity. Am J Physiol Heart Circ Physiol 291: H581-H590, 2006. First published March 3, 2006 doi:10.1152/ajpheart.01279.2005.-Responses to exchange transfusion with red blood cells (RBCs) containing methemoglobin (MetRBC) were studied in an acute isovolemic hemodiluted hamster window chamber model to determine whether oxygen content participates in the regulation of systemic and microvascular conditions during extreme hemodilution. Two isovolemic hemodilution steps were performed with 6% dextran 70 kDa (Dex70) until systemic hematocrit (Hct) was reduced to 18% (Level 2). A third-step hemodilution reduced the functional Hct to 75% of baseline by using either a plasma expander (Dex70) or blood adjusted to 18% Hct with all MetRBCs. In vivo functional capillary density (FCD), microvascular perfusion, and oxygen distribution in microvascular networks were measured by noninvasive methods. Methylene blue was administered intravenously to reduce methemoglobin (rRBC), which increased oxygen content with no change in Hct or viscosity from MetRBC. Final blood viscosities after the entire protocol were 2.1 cP for Dex70 and 2.8 cP for MetRBC (baseline, 4.2 cP). MetRBC had a greater mean arterial pressure (MAP) than did Dex70. FCD was substantially higher for MetRBC [82 (SD 6) of baseline] versus Dex70 [38 (SD 10) of baseline], and reduction of methemoglobin to oxyhemoglobin did not change FCD [84% (SD 5) of baseline]. PO2 levels measured with palladium-meso-tetra(4-carboxyphenyl)porphyrin phosphorescence were significantly changed for Dex70 and MetRBC compared with Level 2 (Hct 18%). Reduction of methemoglobin to oxyhemoglobin partially restored PO2 to Level 2. Wall shear rate and wall shear stress decreased in arterioles and venules for Dex70 and did not change for MetRBC or rRBC. Increased MAP and shear stress-mediated factors could be the possible mechanisms that improved perfusion flow and FCD after exchange for MetRBC. Thus the fall in systemic and microvascular conditions during extreme hemodilution with low-viscosity plasma expanders seems to be, in part, from the decrease in blood viscosity independent of the reduction in oxygen content. microcirculation; extreme hemodilution; plasma expander; intravascular oxygen; methemoglobin; methylene blue; functional capillary density CORRECTION OF BLOOD LOSSES commences with the initial restitution of volume by means of plasma expanders, followed by the reinstatement of oxygen-carrying capacity via blood transfusion on reaching the so-called transfusion trigger. Multiple factors are responsible for reaching this point, including the amount of the blood loss and the dilution due to fluid infused to restore volume. As anemia progresses, oxygenation becomes a concern, when the oxygen-carrying capacity may be insufficient to supply the metabolic demand, and a blood transfusion is performed. The le...
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