Biomedical subjects

Oliver Lenz

Publications and source records attributed to Oliver Lenz.

40 records · Page 3Linked to original sources

PubMedDate not supplied

Overutilization of central venous catheters in incident hemodialysis patients: reasons and potential resolution strategies.

Even after adjusting for comorbidities, the outcomes in hemodialysis (HD) patients using a central venous catheter (CVC) as dialysis access are worse than in those with a permanent vascular access. In spite of this, nationwide data suggest that only about 25% of incident HD patients initiate dialysis with an arteriovenous fistula. We conducted a retrospective study to identify reasons and resolution strategies for CVC use in patients who initiated HD at an academic medical center with a well-established chronic kidney disease (CKD) clinic and a dedicated vascular surgeon. Estimated glomerular filtration rate (eGFR) loss over time to record progression of patients to HD was also examined. The charts of 170 consecutive patients were reviewed. Ninety-two percent were found to initiate HD using a CVC. Three factors explained 93% of all CVC in our cohort: absence of adequate predialysis care (45%), acute illness with failure to recover from an episode of acute renal failure (31%), and patient's failure to adhere to scheduled clinic or surgical appointments (17%). In addition, analyses of eGFR suggest that the velocity of GFR loss rather than a defined degree of renal function might be a better trigger for vascular access referral. We conclude that early referral, a close follow up of CKD patients who initiate dialysis due to acute illness, and patient education may have a positive impact to counteract overutilization of CVCs for dialysis. The rate in eGFR decline might also be used to calculate the referral time adequate for fistula creation.

Acute Kidney Injury↗

PubMedDate not supplied

Utility of static pressure ratio recording during angioplasty of arteriovenous graft stenosis.

Intra-access static pressure ratio (SPR) (intra-access pressure/mean arterial pressure) can be measured during angioplasty (PTA) to assess the functional importance of an arteriovenous graft (AVG) stenosis. We used SPR in 70 patients with AVGs who underwent 98 angioplasty procedures. SPR was measured during angioplasty by placing a catheter tip at mid-access. Inflow stenosis (IF) = stenosis proximal to the tip of the catheter. Outflow stenosis (OF) = stenosis distal to the tip of the catheter up to the superior vena cava-atrial junction. Post PTA, access flow (Qa) was assessed within 2 weeks. Complete data sets for both SPR and Qa were available in 83 procedures. Using a normal SPR ratio of 0.3-0.4 at mid-graft, three patterns of SPR were noted. In 63 of 83 (76%) cases SPR was elevated prior to PTA (0.71 +/- 0.13 SD). PTA reduced SPR toward normal range (0.44 +/- 0.12) in 53 cases (84%). In the remaining 10 (16%), SPR decreased to a low value (0.22 +/- 0.03) and normalized (0.40 +/- .0.11) only after PTA of a coexisting inflow stenosis. In 12 of 83 (14%) procedures, the initial SPR was low (0.18 +/- 0.04) and increased toward normal (0.3 +/- 0.08) following IF stenosis PTA in seven (58%) cases. For the remaining five (42%) cases SPR increased to a high value (0.70 +/- 0.21) and decreased toward normal range (0.33 +/- 0.07) only after OF stenosis angioplasty. In 8 of 83 (10%) procedures, initial SPR was normal (0.33 +/- 0.02). Angiography revealed coexisting IF and OF stenoses. SPR remained within the normal range after PTA of these lesions (0.33 +/- 0.02). Qa increased significantly in 74 of 83 (89%) procedures (before = 572 +/- 201, after = 1109 +/- 368 ml/min; p < 0.001). SPR measurements can assist in hemodynamic assessment of an AVG during angioplasty procedure.

Aged↗

PubMedDate not supplied

Light-driven hydrogen production by a hybrid complex of a [NiFe]-hydrogenase and the cyanobacterial photosystem I.

In order to generate renewable and clean fuels, increasing efforts are focused on the exploitation of photosynthetic microorganisms for the production of molecular hydrogen from water and light. In this study we engineered a 'hard-wired' protein complex consisting of a hydrogenase and photosystem I (hydrogenase-PSI complex) as a direct light-to-hydrogen conversion system. The key component was an artificial fusion protein composed of the membrane-bound [NiFe] hydrogenase from the beta-proteobacterium Ralstonia eutropha H16 and the peripheral PSI subunit PsaE of the cyanobacterium Thermosynechococcus elongatus. The resulting hydrogenase-PsaE fusion protein associated with PsaE-free PSI spontaneously, thereby forming a hydrogenase-PSI complex as confirmed by sucrose-gradient ultracentrifuge and immunoblot analysis. The hydrogenase-PSI complex displayed light-driven hydrogen production at a rate of 0.58 mumol H(2).mg chlorophyll(-1).h(-1). The complex maintained its accessibility to the native electron acceptor ferredoxin. This study provides the first example of a light-driven enzymatic reaction by an artificial complex between a redox enzyme and photosystem I and represents an important step on the way to design a photosynthetic organism that efficiently converts solar energy and water into hydrogen.

Cyanobacteria↗

PubMedDate not supplied

Treatment options for severe lupus nephritis.

Renal involvement in systemic lupus erythematosus is a common complication that significantly worsens morbidity and mortality. Landmark trials conducted by the National Institutes of Health established cyclophosphamide as the mainstay of therapy. Since then, the prognosis of patients with lupus nephritis has markedly improved, and 10-year survival rates now surpass 75%. These superior outcomes have come at the expense of adverse events such as serious infections and gonadal failure in a significant number of patients,and the relapsing nature of the disease continues to pose a problem. For thesereasons, new treatment protocols, such as mycophenolate mofetil induction or sequential therapies using azathioprine or mycophenolate mofetil in the maintenance phase, have been developed in recent years with the goal to maintain remission and reduce adverse events. In addition, ongoing research into the pathogenesis of lupus nephritis has confirmed the importance of B and T cell activation, leading to the identification of potential new therapeutic targets. This article discusses established and novel treatment options for patients with severe lupus nephritis corresponding to WHO classes III, IV, and V withIII or V with IV.

Adrenal Cortex Hormones↗