No abstract

Vascular catheter use for dialysis remains highly prevalent, however, it is frequently adversely affected by access recirculation (AR). We previously reported the utility of effective ionic dialysance (EID)/blood flow rate (Qb) ratio in identifying significant (>5%) AR in arteriovenous (AV) fistulas (Mohan et al ASAIO J 56:427-433, 2010). We present data from 58 patients, receiving hemodialysis via venous catheters (85% tunneled cuffed catheters) who underwent intermittent monitoring for AR with the saline dilution technique (Transonic HD02 monitor) and had EID and Qb measurements from Diascan biosensor in the Gambro Phoenix dialysis machine available. Among the 193 hemodialysis sessions studied, 74 instances of significant access recirculation (sAR) were identified. A higher incidence of sAR occurred with temporary catheters and catheters in the femoral vein. We report a significant correlation between the EID/Qb ratio and AR in addition to demonstrating the predictive utility of the ratio for identifying dysfunction catheters with sAR (area under the receiver operator characteristic curve of 0.86 with a sensitivity of 79% and a specificity of 76% at an EID/Qb ratio of ≤ 0.60). Our data demonstrate the utility of the EID/Qb ratio as an indicator of sAR in dialysis catheters albeit at a different threshold than that seen with AV fistulae.

Abstract. Chronic infection with hepatitis C virus (HCV) has been linked to the development of glomerular disease. HCV infection is highly prevalent among intravenous drug users, a population that is also at risk for HIV coinfection. This study reports the clinical-pathologic features and outcome of HCV-associated glomerular disease (HCV-GD) in 14 patients with HIV coinfection. All were intravenous drug users and all but one were African-Americans. Renal presentations included renal insufficiency, microscopic hematuria with active urine sediment, hypertension, and nephrotic syndrome or nephrotic-range proteinuria without hypercholesterolemia. Hypocomplementemia and cryoglobulinemia were present in 46 and 33% of patients, respectively. The predominant renal biopsy findings were membranoproliferative glomerulonephritis type 1 or type 3 (Burkholder subtype) in 79% of patients and membranous glomerulopathy with atypical features in 21% (including overlap with collapsing glomerulopathy in one patient). The clinical course was characterized by rapid progression to renal failure requiring dialysis. The overall morbidity and mortality were high with median time of 5.8 mo to dialysis or death. Although most patients died in renal failure, cause of death was primarily attributable to long-term immunosuppression and advanced AIDS. Patients with AIDS had shorter survival than those without (median survival time of 6.1 mo versus 45.9 mo, log-rank test P = 0.02). Only two patients were alive with stable renal function at follow-up of 28.5 mo. In patients with HCV-GD, coinfection with HIV leads to an aggressive form of renal disease that can be easily confused with HIV-associated nephropathy. Although hypocomplementemia, cryoglobulinemia, and more prominent hypertension and microscopic hematuria may provide clues to the presence of HCV-GD, renal biopsy is essential to differentiate HCV-GD from HIV-associated nephropathy.

Previous reports have suggested a poor renal prognosis in patients with HIV and HCV co-infection with a preponderance of immune complex mediated glomerular disease on biopsy. Although the benefits of HAART on HIVAN are known, its impact on co-infected patients is unclear. We describe the renal biopsy findings and renal outcome in 29 co-infected patients in the HAART era and compare them to findings in 14 historical controls reported from our institution in the pre-HAART era. Our present cohort was predominantly male and Black with the majority reporting a history of intravenous (i.v.) drug use. Renal biopsy findings included 16 patients with immune complex mediated glomerular disease and 14 patients with FSGS, of which only 3 had collapsing features and/or tubular microcysts typical of HIVAN. Five patients had other biopsy diagnoses not directly related to viral infection. Median renal survival in our cohort was 15.6 months - significantly better than the 1.7 months seen our pre-HAART cohort. The modern cohort's improved renal outcome occurred despite older patients, longer HIV infection and similar levels of renal insufficiency. Our data indicate a changing epidemiology and natural history of renal disease in the HAART era with less immune complex mediated glomerular disease and more non-collapsing FSGS of the usual type. The marked improvement is likely to be multifactorial, including use of antiretroviral and anti-HCV therapies, RAAS antagonists, earlier nephrology referral and generally improved medical care.

A 70-year-old diabetic male patient with a baseline serum creatinine of 1.4 mg/dL presented with nausea and vomiting. He was diagnosed with metformin-associated lactic acidosis and acute kidney injury. He was managed with continuous veno-venous hemodiafiltration (CVVHDF). By measuring metformin concentration at different time intervals, we calculated the apparent volume of distribution of metformin at 34.7 L. The decline in serum metformin followed single-compartment first-order kinetics with an elimination rate constant of 0.0418/h and a serum half-life of 16.5 h; no metformin rebound was seen after discontinuation of CVVHDF. Using the previously calculated volume of distribution we calculated the expected serum metformin concentration 25 h post CVVHDF to be 3.0-3.7 μg/mL. The measured serum metformin of 3.4 μg/ml fell within the predicted range. During CVVHDF, dialyzer metformin clearance approximates 88.7 % of dialyzer urea clearance and 90.1 % of dialyzer creatinine clearance.