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Summary Ischemia time is a prognostic factor in renal transplantation for postoperative graft function and survival. Kidney transplants from living donors have a higher survival rate than deceased donor kidneys probably because of shorter ischemia time. We hypothesized that measurement of intraoperative kidney oxygenation (μHbO2) and microvascular perfusion predicts postoperative graft function. We measured microvascular hemoglobin oxygen saturation by reflectance spectrophotometry and microcirculatory kidney perfusion by laser Doppler flowmetry 5 and 30 min after kidney reperfusion on the organ surface in 53 renal transplant patients including 19 grafts from living donors. These values were related to systemic hemodynamics, cold ischemia time (cit), early postoperative graft function and length of hospital stay. μHbO2 improved 30 min after reperfusion compared to 5 min (from 67% to 71%, P < 0.05). μHbO2 correlated with mean arterial blood pressure and central venous pH (P < 0.01). Most importantly, μHbO2 was significantly higher in kidneys from living compared with deceased donors (74% vs. 63%) and in kidneys without vs. with biopsy‐proven postoperative rejection (71% vs. 45%, P < 0.001). Finally, μHbO2 correlated positively with cit and postoperative creatinine clearance and negatively with postoperative plasma creatinine, need for hemodialysis and length of hospital stay. Our results suggest higher oxygen extraction and thus oxygen demand of the grafts shortly after reperfusion. The intraoperative measurement of tissue oxygenation in kidney transplants is predictive of early postoperative graft function. Future studies should evaluate the potential effect of intraoperative therapeutic maneuvers to improve organ tissue oxygenation in renal transplantation.

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Considerable amounts of heat may be lost or gained through the extracorporeal circuit during hemodialysis and influence the hemodynamic stability of the dialysis patient. The effects of two levels of extracorporeal heat flux (Jtherm in W) on blood pressures and ultrafiltration-induced blood volume changes were studied in eight patients on conventional hemodialysis. Treatments were controlled automatically for mild to medium Jtherm of either -13.4 +/- 3.3 W (group A) or -30.2 +/- 3.7 W (group B) (1 W = 1 J/s = 3.6 kJ/h = 0.239 cal/s = 0.86 kcal/h) and repeated once. Values are given as mean +/- SD. With low blood flows (Qb = 251 +/- 21 ml/min), dialysate temperatures were automatically set at 37.3 +/- 0.3 degrees C (group A) and 35.3 +/- 0.2 degrees C (group B) for the two levels of Jtherm, respectively. Arterial blood temperatures increased by 0.4 +/- 0.4 degree C with mild extracorporeal cooling (group A), whereas arterial blood temperatures slightly decreased by -0.1 +/- 0.4 degree C in the group with medium negative heat flux (group B) (P < 0.01). Blood pressures tended to drop in the warm dialysate group and to remain unchanged in the cool dialysate group (P = NS). Relative blood volume changes calculated from on-line ultrasonic blood measurements were significantly larger with cool (-12.8 +/- 8.3 vol%) than with warm (-7.2 +/- 5.5 vol%, P < 0.05) dialysate, indicating reduced fluid removal from peripheral body compartments during cool hemodialysis ultrafiltration. Despite the larger reduction in intravascular volume, intradialytic hemodynamic stability was maintained with extracorporeal cooling and cool dialysate prescription.