Donation after circulatory death donors (DCD) have the potential to increase the number of heart transplants. The DCD hearts undergo an extended period of warm ischemia, which mandates the use of machine perfusion preservation if they are to be successfully recovered for transplantation. Because the minimum coronary artery flow needed to meet the basal oxygen demand (DCRIT) of a DCD heart during machine perfusion preservation is critical and yet unknown, we studied this in a DCD rat heart model. Adult male rats were anesthetized, intubated, heparinized, and paralyzed with vecuronium. The DCD hearts (n = 9) were recovered 30 minutes after circulatory death whereas non-DCD control hearts (n = 12) were recovered without circulatory death. Hearts were perfused through the aorta with an oxygenated Belzer Modified Machine Perfusion Solution (A3-Bridge to Life Ltd. Columbia, SC) at 15°C or 22°C starting at a flow index of 300 ml/100 g/min and decreasing by 40 ml/100 g/min every 10 minutes. Inflow (aortic) and outflow (inferior vena cava) perfusate samples were collected serially to assess the myocardial oxygen consumption index (MVO2) and O2 extraction ratio. The DCRIT is the minimum coronary flow below which the MVO2 becomes flow dependent. The MVO2, DCRIT, and oxygen extraction ratios were higher in DCD hearts compared with control hearts. The DCRIT for DCD hearts was achieved only at 15°C and was significantly higher (131.6 ± 7 ml/100 g/min) compared with control hearts (107.7 ± 8.4 ml/100 gm/min). The DCD hearts sustain warm ischemic damage and manifest higher metabolic needs during machine perfusion. Establishing adequate coronary perfusion is critical to preserving organ function for potential heart transplantation.
Calcineurin inhibitors remain an integral component of immunosuppressive therapy regimens following solid organ transplantation. Although nephrotoxicity associated with these agents is well documented, type IV renal tubular acidosis is a rare and potentially underreported complication following liver transplantation. Hepatologists must be able to recognize this adverse effect as it can lead to fatal hyperkalemia. We describe a case of tacrolimus-induced hyperkalemic type IV renal tubular acidosis in a patient following an orthotopic liver transplant for alcoholic cirrhosis.
The case of a 39-year-old highly sensitized woman who underwent second renal transplantation after being on warfarin because of a history of frequent thromboses of her left femoral arteriovenous graft (AVG) is reported here. The patient received a flow cytometric positive crossmatch kidney transplant from a deceased donor. Her posttransplant course was complicated by prolonged delayed graft function (DGF) lasting for 9 months. Antibody-mediated rejection occurred in the immediate postoperative period. This resolved after treatment, and resolution was confirmed by repeat biopsy. Despite this, she had persistent DGF and remained dialysis dependent. A computed tomography scan due to the development of perinephric hematoma after posttransplant biopsy demonstrated venous collateralization around the allograft. At 7 months posttransplant, a venogram during declotting of AVG revealed chronic thrombus in the inferior vena cava (IVC) above the level of native renal veins with a venous gradient of 26 mmHg. After declotting of the graft, iliac venoplasty, and subsequent IVC stent, her renal function continues to improve with a most recent creatinine of 1.4 mg/dL at 36 months posttransplant. Venous hypertension secondary to IVC thrombosis in presence of patent femoral AVG should be considered as a rare cause of prolonged DGF.
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