Occult infection of old nonfunctioning arteriovenous grafts: a novel cause of erythropoietin resistance and chronic inflammation in hemodialysis patients.

BACKGROUND: Occult infection of old nonfunctioning arteriovenous grafts (AVGs) is frequent among hemodialysis patients. It is a recognized cause of bacteremia and other infectious complications. Additionally, old nonfunctioning AVGs may be harbingers of other noninfectious complications. The aim of this study was to investigate whether occult infection of old nonfunctioning AVGs is a cause of a chronic inflammatory state in hemodialysis patients.
METHODS: This study was performed in two phases: In the first phase (study 1), 22 patients with clinically proven occult infection of old nonfunctioning AVG were identified, and data on hemoglobin, weekly erythropoietin dose, and albumin levels were collected retrospectively. Comparisons were made between values obtained pre- and post-AVG resection. In the second phase (study 2), we examined whether the presence of a chronic inflammatory state is associated with occult AVG infection in old nonfunctioning AVGs. Twenty hemodialysis patients were identified with chronic inflammatory state based on erythropoietin dose (units/wk)/hematocrit ratio>470, serum albumin <3.3 g/dL, and CRP>25 mg/L. Among these patients, we found eight with old nonfunctioning AVGs. We then performed indium-labeled white blood cell (WBC) scans on the eight patients to screen for occult infection of old nonfunctioning AVGs. The AVGs with positive indium scan were resected and cultured. Data on hematocrit, erythropoietin dosing, serum albumin, ferritin, and CRP were obtained at 2 months following AVG resection and compared to pre-resection values.
RESULTS: In study 1, the 22 patients with occult infection of old nonfunctioning AVG exhibited profound anemia and hypoalbuminemia. Their mean hemoglobin was 9.2 +/- 1.2 g/dL which improved to 11.6 +/- 0.8 g/dL (P < 0.05) 3 months after AVG resection. Their mean serum albumin was 3.3 +/- 0.5 g/dL which improved to 3.8 +/- 0.2 g/dL (P < 0.05) 3 months after AVG resection. Their mean erythropoietin dosages (units/patient/wk) fell from 14,240 +/- 350 to 6,675 +/- 455 (P < 0.05). In study 2, among the 8 patients with chronic inflammatory state and old nonfunctioning AVG, 6 (75%) had positive indium scans and underwent surgical resection that proved bacterial infection. Upon follow-up, the 2-month data showed a remarkable improvement in the following parameters: weekly erythropoietin dose/hematocrit ratio from 622 +/- 137 to 254 +/- 28 (P < 0.05), plasma ferritin values from 690 +/- 126 ng/mL to 247 +/- 42 ng/mL (P < 0.01), and plasma CRP from 56.7 +/- 9.0 to 14.5 +/- 3.8 mg/L (P < 0.01). Serum albumin values also improved from 3.07 +/- 0.08 g/dL to 3.34 +/- 0.14 g/dL (P = 0.13). Percent plasma iron saturation did not appreciably differ from baseline (20.5% +/- 4.4% to 19.8 +/- 1.9%, P = 0.89).
CONCLUSIONS: Occult infection of old nonfunctioning AVG is a common cause of erythropoietin resistance and chronic inflammatory state among hemodialysis patients. Resection of old nonfunctioning AVGs with occult infection is associated with resolution of markers of chronic inflammatory state.