Evaluation of Enoxaparin Dosing as a Risk Factor for Bleeding in Lung Transplant Recipients.

BACKGROUND: Lung transplant recipients commonly develop complications that lead to anticoagulation. Standard FDA-approved enoxaparin dosing in this population results in a high incidence of above-goal anti-Xa levels, but its association with bleeding remains unclear. OBJECTIVE: To evaluate the association between enoxaparin dosing and bleeding in lung transplant recipients and assess the relationship between dosing and anti-Xa levels. METHODS: We conducted a single-center retrospective cohort study of adult lung transplant recipients who received therapeutic enoxaparin between 2000 and 2012 at a tertiary academic center. We dichotomized enoxaparin dosing regimens into standard dose (FDA-approved doses with a 10% rounding margin) and reduced dose. Clinicians ordered anti-Xa levels as deemed clinically appropriate. The primary outcome was major bleeding or clinically relevant nonmajor bleeding. RESULTS: Of 222 patients treated with enoxaparin, 33 (14.9%) had bleeding events, of which half (17/33) were major. Bleeding occurred in 25/146 (17.1%) patients who received standard-dose enoxaparin versus 8/76 (10.5%) patients who received reduced-dose enoxaparin (P = 0.190). Multiple logistic regression demonstrated an independent association between standard-dose enoxaparin and bleeding, after adjusting for confounders (adjusted odds ratio = 3.04; 95% CI = 1.14-8.10). The median enoxaparin dose in patients with above-goal versus at-goal anti-Xa levels was 0.89 versus 0.76 mg/kg every 12 hours; P = 0.006. However, doses yielding at-goal anti-Xa levels had an interquartile range of 0.67 to 0.90 mg/kg, which overlapped with doses yielding above- and below-goal anti-Xa levels. CONCLUSIONS: Enoxaparin dose reduction and anti-Xa level monitoring can improve drug safety and facilitate individualized dose optimization in lung transplant recipients.

Hyperammonemia Syndrome After Lung Transplantation: A Single Center Experience.

BACKGROUND: Hyperammonemia is a rare, often fatal complication after transplantation. The etiology is unknown, but recognition and rapid treatment may help to improve the survival of this unusual syndrome. We present the largest case series to date of hyperammonemia after lung transplantation (LTx) and discuss a treatment protocol that has been developed at our institution. METHODS: We conducted a retrospective cohort series of patients who underwent LTx between January 1, 2000, and December 31, 2013. Patients who developed hyperammonemia syndrome in the posttransplantation period, which was defined as symptoms of encephalopathy and plasma ammonia level exceeding 200 µmol/L on at least 1 occasion, were included. Data including demographics, antimicrobial and immunosuppression regimens, ammonia levels and other pertinent laboratory data, treatments administered, and outcomes were recorded. RESULTS: Eight of 807 lung transplant recipients developed hyperammonemia syndrome postoperatively during this time period. Median time to onset was 9.0 days, and median peak ammonia level was 370 µmol/L. All 8 patients were treated with hemodialysis, 7 of 8 patients were treated with bowel decontamination, and 5 of 8 patients were treated with nitrogen scavenging agents. Six of the 8 patients died. CONCLUSIONS: The incidence of hyperammonemia syndrome in LTx patients was approximately 1%. Future research is needed to determine the efficacy of treatment, including hemodialysis, bowel decontamination, antibiotics, and the use of nitrogen scavenging agents in lung recipients with hyperammonemia.

Analysis of enoxaparin dose titration at a large, tertiary teaching facility.

Therapeutic drug monitoring of enoxaparin with antifactor Xa levels (AXALs) is recommended in some populations; however, the approach to dose titration is poorly described. Our study at a large, tertiary teaching facility examined the dose response to titration of enoxaparin based on AXAL. Patients from 2008 to 2012 receiving enoxaparin were included, provided 2 or more steady state AXAL were obtained within 30 days and that the enoxaparin was prescribed for treatment rather than prophylaxis. The primary outcome was the percentage of dose change required to obtain goal range AXAL following dose titration. Eighty-seven patients were available for analysis with the following key characteristics: renal dysfunction during treatment 72%, obesity 8%, and solid organ transplant 26%. Initial goal AXAL was attained in 27 (31%) patients, and ultimately 54 (62%) patients achieved goal AXAL. Of the 31 patients who had initial AXAL above goal, 13 (42%) patients reached goal with a median dose decrease of 24%. In the 29 patients who had an initial AXAL below goal, 11 (38%) achieved therapeutic AXAL with a median dose increase of 16%. The AXAL monitoring can guide enoxaparin titration with subtherapeutic or supratherapeutic AXAL and an increase or decrease of roughly 20% is suggested as an initial change.

Acute antibody-mediated rejection after lung transplantation.

BACKGROUND: Antibody-mediated rejection (AMR) after lung transplantation remains enigmatic, and there is no consensus on the characteristic clinical, immunologic and histologic features. METHODS: We performed a retrospective, single-center cohort study and identified cases of acute AMR based on the presence of circulating donor-specific human leukocyte antigen (HLA) antibodies (DSA), histologic evidence of acute lung injury, C4d deposition and clinical allograft dysfunction. RESULTS: We identified 21 recipients with acute AMR based on the aforementioned criteria. AMR occurred a median 258 days after transplantation; 7 recipients developed AMR within 45 days of transplantation. All patients had clinical allograft dysfunction, DSA, histology of acute lung injury and capillary endothelial C4d deposition. Fifteen recipients improved clinically and survived to hospital discharge, but 6 died of refractory AMR. One survivor had bronchiolitis obliterans syndrome at the time of AMR diagnosis; 13 of the 14 remaining survivors developed chronic lung allograft dysfunction (CLAD) during follow-up. Overall, 15 recipients died during the study period, and the median survival after the diagnosis of AMR was 593 days. CONCLUSIONS: Acute AMR can be a fulminant form of lung rejection, and survivors are at increased risk of developing CLAD. The constellation of acute lung injury, DSA and capillary endothelial C4d deposition is compelling for acute AMR in recipients with allograft dysfunction. This clinicopathologic definition requires validation in a multicenter cohort, but may serve as a foundation for future studies to further characterize AMR.