Effect of increased pressure during pulsatile pump perfusion of deceased donor kidneys in transplantation

INTRODUCTION

Pulsatile pump perfusion of potential kidneys for transplantation is known to decrease the rate of delayed graft function (DGF) and improve their 1-year survival. Flow and resistance parameters are often used to determine the suitability of kidneys for transplantation. Kidneys with low flow rates are often subjected to higher pressures to improve flow. This study evaluated the effect of higher pump pressures on posttransplant renal function.

METHODS

We performed a retrospective analysis of 73 deceased donor kidneys preserved using pump perfusion (LifePort) at our center between May 2006 and September 2009. We calculated the mean pump pressure (MP) for the duration of perfusion of each kidney, using systolic pressure (SP) and diastolic pressure (DP) readings with the following formula: (MP = DP + 1/3 (SP - DP). The kidneys were divided into a low (LP; n = 49) and a high-pressure group (HP; n = 24) based on a MP cutoff value of 23 mm Hg. The two groups were then compared for differences in perfusion dynamics and primary endpoints including DGF and 1-year graft survival. Statistical analysis was performed using paired Student t test and chi-square analysis.

RESULTS

The two groups were comparable for donor age, extended criteria, sensitization, and cold ischemic times. They differed significantly in higher initial (0.65 ± 0.4 versus 0.4 ± 0.2, P = .01), average (0.25 ± 0.08 versus 0.18 ± 0.06, P = .0006), and terminal resistance (0.21 ± 0.07 versus 0.17 ± 0.06, P = .008) of HP versus LP kidneys. Flow rates were comparable between the two groups. DGF was higher in HP kidneys (75% versus 40%, P = .006) with similar 1-year graft survival (87.5% versus 89%, P = .7).

CONCLUSIONS

Perfusate flow through a kidney can be improved by increasing pressure settings to overcome elevated resistance. This maneuver was not associated with a lower rate of DGF after transplantation. One-year graft survival remained unaffected.

Conversion to low-dose tacrolimus or rapamycin 3 months after kidney transplantation: a prospective, protocol biopsy-guided study

Long-term survival of kidney allografts is primarily limited by a progressive decline in function characterized by the presence of interstitial fibrosis (IF) and tubular atrophy (TA) on biopsy. Since chronic calcineurin-inhibitor (CNI) drug toxicity has been implicated as a significant cause of IF/TA, a major effort in transplantation has been to decrease or eliminate CNI therapy. We now report the clinical and histological consequences of converting renal transplant recipients at 3 months to either very low levels of tacrolimus (TAC; 4-6 ng/mL) or sirolimus (SRL; 6-10 ng/mL) therapy. Fifty-eight enrollees in this prospective randomized trial received low-dose (2.9±0.6 mg/kg) rabbit antithymocyte globulin induction followed by standard doses of TAC (10-15 ng/mL), mycophenolic acid, and low-dose steroids for 3 months. Protocol biopsies were performed at implantation and 3 and 12 months. Six patients had evidence of either borderline changes (n=5) or grade 1A rejection (n=1) on the 3-month protocol biopsy and were not randomized. Only one patient had clinically evident rejection that occurred after randomization to SRL. One patient in each group had borderline changes at 12 months. Renal function (estimated glomerular filtration rate) was equivalent in both groups at 12 months (TAC 74±15 vs SRL 66±18 mL/min, P=.22). Chronic allograft damage index scores at 1 year were similar in both groups (TAC 2.8±2.4 vs SRL 2.0±2.7, P=.71). The percentage of patients with IF/TA scores greater than 2 at 1 year was low in both groups (TAC 12% vs SRL 9%, P=.78). Therefore, in a low-risk population defined as having a normal 3-month protocol biopsy, TAC levels can be successfully decreased to very low concentrations. One-year graft function and histology were equally well maintained with either low-dose TAC or SRL immunosuppression.